Farnell | Electronic Component Distributors · 2009. 2. 27. · Information About Cautions and...
Transcript of Farnell | Electronic Component Distributors · 2009. 2. 27. · Information About Cautions and...
April 2002 Data Acquisition Products
User’s Guide
SLAU083
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications,enhancements, improvements, and other changes to its products and services at any time and to discontinueany product or service without notice. Customers should obtain the latest relevant information before placingorders and should verify that such information is current and complete. All products are sold subject to TI’s termsand conditions of sale supplied at the time of order acknowledgment.
TI warrants performance of its hardware products to the specifications applicable at the time of sale inaccordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TIdeems necessary to support this warranty. Except where mandated by government requirements, testing of allparameters of each product is not necessarily performed.
TI assumes no liability for applications assistance or customer product design. Customers are responsible fortheir products and applications using TI components. To minimize the risks associated with customer productsand applications, customers should provide adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right,copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or processin which TI products or services are used. Information published by TI regarding third–party products or servicesdoes not constitute a license from TI to use such products or services or a warranty or endorsement thereof.Use of such information may require a license from a third party under the patents or other intellectual propertyof the third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of information in TI data books or data sheets is permissible only if reproduction is withoutalteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproductionof this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable forsuch altered documentation.
Resale of TI products or services with statements different from or beyond the parameters stated by TI for thatproduct or service voids all express and any implied warranties for the associated TI product or service andis an unfair and deceptive business practice. TI is not responsible or liable for any such statements.
Mailing Address:
Texas InstrumentsPost Office Box 655303Dallas, Texas 75265
Copyright 2002, Texas Instruments Incorporated
EVM IMPORTANT NOTICE
Texas Instruments (TI) provides the enclosed product(s) under the following conditions:
This evaluation kit being sold by TI is intended for use for ENGINEERING DEVELOPMENT OR EVALUATIONPURPOSES ONLY and is not considered by TI to be fit for commercial use. As such, the goods being providedmay not be complete in terms of required design-, marketing-, and/or manufacturing-related protectiveconsiderations, including product safety measures typically found in the end product incorporating the goods.As a prototype, this product does not fall within the scope of the European Union directive on electromagneticcompatibility and therefore may not meet the technical requirements of the directive.
Should this evaluation kit not meet the specifications indicated in the EVM User’s Guide, the kit may be returnedwithin 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVEWARRANTY MADE BY SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED,IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANYPARTICULAR PURPOSE.
The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the userindemnifies TI from all claims arising from the handling or use of the goods. Please be aware that the productsreceived may not be regulatory compliant or agency certified (FCC, UL, CE, etc.). Due to the open constructionof the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostaticdischarge.
EXCEPT TO THE EXTENT OF THE INDEMNITY SET FORTH ABOVE, NEITHER PARTY SHALL BE LIABLETO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.
TI currently deals with a variety of customers for products, and therefore our arrangement with the user is notexclusive.
TI assumes no liability for applications assistance, customer product design, software performance, orinfringement of patents or services described herein.
Please read the EVM User’s Guide and, specifically, the EVM Warnings and Restrictions notice in the EVMUser’s Guide prior to handling the product. This notice contains important safety information about temperaturesand voltages. For further safety concerns, please contact the TI application engineer.
Persons handling the product must have electronics training and observe good laboratory practice standards.
No license is granted under any patent right or other intellectual property right of TI covering or relating to anymachine, process, or combination in which such TI products or services might be or are used.
Mailing Address:
Texas InstrumentsPost Office Box 655303Dallas, Texas 75265
Copyright 2002, Texas Instruments Incorporated
EVM WARNINGS AND RESTRICTIONS
It is important to operate this EVM within the power supply voltage range of 5.5 V to 15 V (5 V for regulated power inputs) and the analog input range of 0 V to 5 V.
Exceeding the specified supply range may cause unexpected operation and/or irreversibledamage to the EVM. If there are questions concerning the supply range, please contact a TIfield representative prior to connecting the input power.
Applying loads outside of the specified output range may result in unintended operation and/orpossible permanent damage to the EVM. Please consult the EVM User’s Guide prior toconnecting any load to the EVM output. If there is uncertainty as to the load specification,please contact a TI field representative.
During normal operation, some circuit components may have case temperatures greater than40°C. The EVM is designed to operate properly with certain components above 40°C as longas the input and output ranges are maintained. These components include but are not limitedto linear regulators, switching transistors, pass transistors, and current sense resistors. Thesetypes of devices can be identified using the EVM schematic located in the EVM User’s Guide.When placing measurement probes near these devices during operation, please be awarethat these devices may be very warm to the touch.
Mailing Address:
Texas InstrumentsPost Office Box 655303Dallas, Texas 75265
Copyright 2002, Texas Instruments Incorporated
Information About Cautions and Warnings
iii
Preface
About This Manual
This users guide describes the function and operation of the ADS1254EVManalog-to-digital converter evaluation module. This manual helps you quicklyset up the evaluation module and its accompanying software, so that you canrapidly test and evaluate the ADS1254. Complete circuit descriptions, as wellas schematic diagrams, PCB layouts, and bill of materials, are also included.
How to Use This Manual
This manual begins with an introductory chapter which describes the EVM andwhat it can do. If you are anxious to set things up and start testing, we suggestyou read at least the first two chapters. These two chapters introduce you tothe board and how to set it up to start working with it.
Information About Cautions and Warnings
This book may contain cautions and warnings.
This is an example of a caution statement.
A caution statement describes a situation that could potentiallydamage your software or equipment.
This is an example of a warning statement.
A warning statement describes a situation that could potentiallycause harm to you.
The information in a caution or a warning is provided for your protection.Please read each caution and warning carefully.
Trademarks
iv
Related Documentation From Texas Instruments
Data Sheets Literature Number
ADS1254 SBAS213MAX3238 SLLS349MSP430F149 SLAS272REG1117 SBVS001REG103 SBVS010OPA350 SBOS099SN74LVC1G07 SCES296SN74LVC1G08 SCES217SN74LVC1G125 SCES223
FCC Warning
This equipment is intended for use in a laboratory test environment only. It gen-erates, uses, and can radiate radio frequency energy and has not been testedfor compliance with the limits of computing devices pursuant to subpart J ofpart 15 of FCC rules, which are designed to provide reasonable protectionagainst radio frequency interference. Operation of this equipment in other en-vironments may cause interference with radio communications, in which casethe user at his own expense will be required to take whatever measures maybe required to correct this interference.
Trademarks
Windows is a trademark of Microsoft Corporation.
If You Need Assistance. . .
If you have questions about this or other Texas Instruments data converterevaluation modules, feel free to e–mail the data converter application team [email protected]. Include the product name in the subject heading.
Contents
v
1 Introduction 1-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 The ADS1254 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 EVM System Overview 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Analog Inputs 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Prototyping Area 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Power Requirements 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Host Computer Requirements 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Getting Started 2-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 Unpacking the EVM 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Default Configuration 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Quick Start 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3 Operation 3-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Jumpers 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.1.1 JMP1: Reference Source Select 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 JMP2, JMP3: Power Source Select 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 JMP4: Reference Disconnect 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 JMP5: MCU Disable 3-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Reset Switch 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Connectors 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1 J7: RS-232 Connector 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 J6: 3.3-V JTAG Port 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 J1, J4, J5, BT1: Power Connectors 3-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.4 J2: Analog Inputs 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.5 J3: External Reference Input 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.6 J8: External Digital Control 3-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.7 J9, J10: DSK Motherboard Connectors 3-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.8 TP1–6: Test Point 3-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 Circuit Description 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 ADS1254 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Microcontroller 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 Clock Generation 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.4 Firmware and Host Communication 3-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.5 Power Supply 3-11. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 Host PC Software 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Main Window 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.2 Display Modes 3-14. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.3 Setup Dialog 3-15. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Contents
vi
4 Physical Description 4-1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 Board Layouts 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Schematics 4-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figures
1–1 ADS1254EVM Block Diagram 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1–2 ADS1254EVM Component Locations 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2–1 Start-Up Display 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–1 Main Window 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3–2 Setup Dialog 3-16. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4–1 Board Layout Top Layer 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–2 Board Layout Bottom Layer 4-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–3 Schematic (Sheet 1 of 2) 4-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4–4 Schematic (Sheet 2 of 2) 4-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tables
2–1 Factory Jumper Settings 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–1 Jumper/Function Reference 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–2 J7: RS-232 Port Pinout 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–3 J8: 3.3-V JTAG Port 3-5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–4 J1: Unregulated Power Input Connector 3-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–5 J4: External Digital Power Supply Input Connector 3-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–6 J5: External Analog Power Supply Input Connector 3-6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–7 BT1: 9-V Battery Connector 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–8 J2: Analog Inputs 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–9 J3: External Reference Input 3-7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–10 J8: 3.3-V JTAG Port 3-8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3–11 TP1–6: Test Points 3-9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1-1
This chapter provides an overview of the ADS1254EVM evaluation moduleand software.
Topic Page
1.1 The ADS1254 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.2 EVM System Overview 1-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.3 Analog Inputs 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.4 Prototyping Area 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.5 Power Requirements 1-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1.6 Host Computer Requirements 1-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 1
The ADS1254
1-2
1.1 The ADS1254
The ADS1254 is a precision 24-bit delta-sigma analog-to-digital converter withfour differential input channels. The delta-sigma architecture employed in theADS1254 enables the device to achieve 19 bits of effective resolution (1.8 ppmRMS noise) at data rates of up to 20 kHz. The part also has a no-missing-codescharacteristic across the full 24 bit range.
The ADS1254 employs an unidirectional two-wire synchronous serialinterface (modified SPI) for communication with the host system. Isolation canbe applied to this interface at minimal cost.
1.2 EVM System Overview
A block diagram of the ADS1254 evaluation module is shown in Figure 1–1.
Figure 1–1. ADS1254EVM Block Diagram
RS-232Serial Port
MSP430F149Microcontroller
128 k × 8SRAM
ClockGenerator
ADS1254
ReferenceBuffer
Serial Data
SPI
Inputs
Reference Inputs
SystemClock
During normal operation, data is read from the ADS1254 into the user’scomputer via the ADS1254EVMs RS-232 port. Once read, the data can bedisplayed and analyzed in a variety of ways using the supplied ADS1254EVMsoftware.
The ADS1254 can supply data much faster than it can be transmitted to thehost PC over the RS-232 connection. Because of this, data read from theADS1254 is stored in an onboard RAM, where it is kept until retrieved by thehost system. This process is controlled by the user through the ADS1254EVMsoftware.
Analog Inputs
1-3Introduction
The ADS1254EVM incorporates a PLL-based clock generator which cansynthesize clocks of nearly arbitrary frequency up to the maximum of 8 MHz.The PLL exhibits increased jitter, so for certain clock frequencies, a directdivide-down circuit derived from a crystal oscillator is used instead. Thedivide-down is selected automatically.
The ADS1254EVM can be powered using an ac power adapter (not included),a 9-volt battery, or a user-supplied laboratory power supply.
A photograph of the ADS1254EVM with the locations of major componentshighlighted is shown in Figure 1–2.
Figure 1–2. ADS1254EVM Component Locations
CHANNEL INPUTS
EXTERNALREFERENCE
INPUT
RS-232 PORT
ANALOGREGULATED
POWER
DIGITALREGULATED
POWER
UNREGULATEDPOWER
JTAGADS1254
BATTERYCONNECTOR
MCU DISABLE VREF DISCONNECTVREF SOURCE SELECT
DIGITAL VDD SOURCE
ANALOG VDD SOURCE
SRAM
MCU
DSK PERIPHERAL CONNECTOR
DSK MEMORY CONNECTOR
EXT DIGITAL
1.3 Analog InputsAnalog input is supplied through the eight-way screw terminal block, J2. Eachinput is connected to the ADS1254 through a 1-kΩ resistor. The inputs are notprotected against overvoltage.
1.4 Prototyping AreaA prototyping area is provided on the ADS1254EVM. This may be used toincorporate additional circuitry, such as special reference or conditioningcircuits, into the system. Certain holes are connected to convenient circuitpoints, such as ground, reference, etc.
1.5 Power RequirementsThe ADS1254EVM must be supplied with 5.5 V–15 V for proper operation.Power can be supplied through barrel jack, J1 (tip positive), screw terminalblocks J4 and J5, or with a 9-volt battery connected to battery snap BT1.
Host Computer Requirements
1-4
1.6 Host Computer Requirements
The ADS1254EVM software is designed to run on a PC running anyWindows platform (Windows 95, 98, NT, 2000, etc.).
Minimum Requirements:
IBM-compatible 486 PC or higher
Windows 95/98/2000 or NT4.0
64 MB RAM minimum
20 MB available hard disk space
CD-ROM drive
Available serial port
2-1Getting Started
This chapter guides you through unpacking your EVM and setting it up so youcan begin working with it immediately.
Topic Page
2.1 Unpacking the EVM 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.2 Default Configuration 2-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.3 Quick Start 2-3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 2
Unpacking the EVM
2-2
2.1 Unpacking the EVM
After unpacking the ADS1254EVM kit, check to make sure you received all ofthe items listed here:
ADS1254EVM board
9-pin D-sub male-female serial cable
Software CD-ROM
If any of these items are missing, contact Texas Instruments to receivereplacements.
2.2 Default Configuration
Although much of the ADS1254EVMs operation is controlled by the host PC,some configuration must be done directly on the board, using five jumpers(shorting blocks). The ADS1254EVM is configured as follows at the factory:
Table 2–1.Factory Jumper Settings
Jumper Identifier Description Default Setting
JMP1 External reference select 2–3
JMP2 Digital power supply source 1–2
JMP3 Analog power supply source 1–2
JMP4 Reference disconnect 1–2
JMP5 MCU disable Disconnected
For more information about the jumpers, see Section 3.1.
Quick Start
2-3Getting Started
2.3 Quick Start
Once the ADS1254EVM has been unpacked from its shipping container, andyou have verified that the board is configured as shown in Table 2–1, it can bepowered on and tested.
First, connect the board to the host PC using the supplied 9-pin serial cable.Then power the board on by plugging a wall power adapter into a suitable acpower source and plugging the barrel plug into the barrel jack on theADS1254EVM, or by connecting your laboratory power supply to the externalpower inputs and setting JMP2 and JMP3 to the 2–3 position. (You do not haveto connect the serial cable first; it is also acceptable to apply power to the boardfirst.) When the board is properly powered on, the two power good indicatorlamps near the power connectors glow brightly. (The 5-V LED may glowbrighter than the 3.3-V LED; this is normal.)
Place the CD-ROM into your PCs CD-ROM drive. Locate the setup programon the disk, and run it. The setup program installs the ADS1254EVM softwareon your PC. If you are running a Windows platform that is NT-based, such asWindows NT or Windows 2000, you need administrator privileges to install thesoftware. Follow the instructions that the installer gives you.
Once the program has been successfully installed, it can be executed. Whenthe program is run, it displays a title screen, and then you see something likethe display in Figure 2–1.
Figure 2–1. Start-Up Display
Quick Start
2-4
The setup window appears first, allowing you to make adjustments to theprograms configuration. For the test run, you should select the serial port towhich the ADS1254EVM is connected, using the serial port menu.
If no serial ports are available, a message box appears informing you that theprogram cannot run. This is usually because other programs are using all ofthe available serial ports. If this is the case, closing these programs andrerunning the program should fix the problem.
Once the correct serial port has been selected, click OK. The setup dialogdisappears and you see the main window. Click the acquire button. After aperiod of activity, you see data displayed in the data display window.
3-1Operation
This chapter describes each function of the ADS1254EVM, and how to use theaccompanying software to control the ADS1254.
Topic Page
3.1 Jumpers 3-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2 Reset Switch 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3 Connectors 3-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4 Circuit Description 3-10. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5 Host PC Software 3-12. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 3
Jumpers
3-2
3.1 Jumpers
Table 3–1 shows the function of each jumper on the EVM:
Table 3–1.Jumper/Function Reference
ReferenceDesignator
Setting Function Default Section
JMP1 1 to 2 External reference 2–3 Section 3.1.1
2 to 3 Onboard reference
JMP2 1 to 2 Digital power supplied from barreljack, battery, or DSK
1–2 Section 3.1.2
2 to 3 Digital power supplied from screwterminal block J4
JMP3 1 to 2 Analog power supplied from barreljack, battery, or DSK
1–2 Section 3.1.2
2 to 3 Analog power supplied from screwterminal block J4
JMP4 Connected Reference pin is connected Connected Section 3.1.3
Disconnected Reference pin is not connected
JMP5 Connected MCU controls ADS1254 Disconnected Section 3.1.4
Disconnected MCU does not control ADS1254
3.1.1 JMP1: Reference Source Select
The ADS1254EVM can use an externally supplied reference or an onboard4.096-V zener reference (D1 and R1); use JMP1 to connect the desiredreference source. Shorting pins 1 and 2 connects the external reference;shorting pins 2–3 connects the onboard reference.
3.1.2 JMP2, JMP3: Power Source Select
The ADS1254 has separate analog and digital power supplies. JMP2 is usedto select the source for the digital power supply, and JMP3 is used to selectthe source for the analog supply. To use the barrel jack or battery (onboardregulator), short pins 1–2; if you wish to use an external power supply, shortpins 2–3.
3.1.3 JMP4: Reference Disconnect
JMP4 is used to connect an external reference directly to the ADS1254, with-out using the onboard filtering. Removing this jumper disconnects theADS1254 reference pin. External reference voltage must be applied to pin 2.
Jumpers
3-3Operation
3.1.4 JMP5: MCU Disable
Shorting the pins of this jumper has the same effect as plugging theADS1254EVM into a DSP DSK: the onboard regulators are shut down, and ifpower is still available, the MCU is disabled. Power may still be suppliedthrough the external power connectors J4 and J5, or through the DSK;however, power cannot be supplied to the onboard clock generator from theDSK, since the clock generator is only supplied from the onboard regulators.
If you want to use an external system to control the ADS1254, instead of theonboard MCU, you must connect this jumper to prevent conflicts with the MCU.Since this jumper disables the onboard power supply, you must also power theboard externally.
If JMP5 is shorted, and power is available to the MCU, it is active, but iteffectively disconnects itself from the ADS1254 by 3-stating any pins leadingto the 1254. This prevents conflicts with the DSK. The MCU can stillcommunicate with the host PC in this mode.
Reset Switch
3-4
3.2 Reset Switch
Switch SW1 is a miniature pushbutton which, when pressed, forces the MCUsRESET line low. When released, the MCU enters a reset cycle. Ifcommunication becomes disrupted between the host and the board, or theboard is unresponsive, pressing RESET returns the system to normaloperation.
3.3 Connectors
The various connectors on the ADS1254EVM are described in this section.
3.3.1 J7: RS-232 Connector
The host PC controls the board through this connector, which is a 9-pin femaleD-shell type, pinned out in the usual manner. Certain of the flow control linesare used for special purposes by the ADS1254EVM board; these aredescribed in the table.
In the RS-232 electrical specification, –5 V to –15 V on a line indicates a logichigh (mark), and 5 V to 15 V indicates logic low (space). Line states aredescribed here according to their logical states.
If a non-handshaking RS-232 cable is used, that is, one which connects onlyRD, TD, and signal ground. The board can still operate normally, but it cannotbe reset by the host PC, and bootstrap firmware upgrading cannot beperformed through the serial port (it can still be done through the JTAG portJ6, but this requires a special programming adapter and software).
Table 3–2.J7: RS-232 Port Pinout
PinNumber
SignalName
RS-232 Name Direction(at board)
Function
1 DCD Data carrier detect Output None
2 RD Receive data Output Serial data output to host PC
3 TD Transmit data Input Serial data input from host PC
4 DTR Data terminal ready Input Connected to the MCUs reset circuit. A lowon this line resets the MCU. Must be heldhigh for normal operation
5 SG Signal ground Power Ground reference
6 DSR Data set ready Output None
7 RTS Request to send Input Connected to TCK on MCU. Used for boot-strap firmware loading. Must be held highfor normal operation
8 CTS Clear to send Output None
9 RI Ring indicator Output None
Connectors
3-5Operation
3.3.2 J6: 3.3-V JTAG Port
This connector is used mainly during firmware development. It provides a fastway to download firmware into the MCU, and also allows access to the MCU’shardware debugging features. If you have MSP430 software developmenttools, you can use this port to write your own firmware for the ADS1254EVM.
This port is designed for use only with 3.3-V JTAG tools, such as thoseprovided by TI for use with the MSP430. If you attempt to use 5-V JTAGtools with this port, you permanently damage the MSP430, as it is not 5-Vtolerant.
Table 3–3.J8: 3.3-V JTAG Port
Pin Num-ber
PinSymbol
Signal Name Direction(at board)
Function
1 TDI/TDO Test data in/out Output JTAG TDO port (see JTAG standard)
2 VCCTOOL Power from JTAGadapter
Power JTAG adapter–provided power supply(not used on ADS1254EVM)
3 TDI/VPP Test data in/pro-gramming voltage
Input Used as a test data input, and for blowingthe security fuse
4 VCCLOCAL Power sensefrom board
Output High rail from board; used for signal sensewhen board is using its own power supplyduring programming
5 TMS Test mode select Input JTAG test mode select pin (see JTAGstandard)
6 NC Not connected – Not used
7 TCK Test clock Input JTAG serial clock input (see JTAGstandard)
8 NC Not connected – Not used
9 GND Ground Power Signal ground
10 NC Not connected – Not used
11 RST/NMI Reset/non-mask-able interrupt
Input MCU reset line
12 NC Not connected – Not used
13 NC Not connected – Not used
14 NC Not connected – Not used
Connectors
3-6
3.3.3 J1, J4, J5, BT1: Power Connectors
The ADS1254EVM features a flexible power supply. Externally generatedpower, the onboard regulator circuitry and an ac adaptor, or a 9-V battery mayall be used to supply power. Furthermore, the separated analog and digitalpower supplies may be powered differently; for example, the analog powersupply may be powered externally, and the digital power supply may use thebuilt-in regulator, at the same time. (This is configured using jumpers JMP2and JMP3.) The exception to this is that the battery and ac adaptor cannot beused at the same time (see below).
An additional source of power may come from a DSP development board(DSK). When the ADS1254EVM is plugged in to a DSK motherboard, theonboard regulators are shut down, and power is sourced from the DSK. TheDSK’s power supply, however, may not be suitable for powering the analogcircuitry, as it is likely to be somewhat dirty, so for best performance it isnecessary to use an external supply for the analog circuitry when using theADS1254EVM with a DSK.
Four power connectors are provided: screw terminal blocks J4 and J5 forexternal power, battery terminal BT1 for a 9-V transistor radio battery, and J1for a wall-wart. J1 is a switched jack: connecting a plug to J1 automaticallydisconnects the battery terminal. This prevents the battery and J1 fromsupplying power simultaneously.
Battery power is regulated by the same circuitry that regulates J1 (wall-wart)power.
Be very careful when connecting external power supplies to J4 and J5.They are not protected against reversed polarity. If you connect thembackwards (that is, with reversed polarity), permanent damage to theADS1254EVM is likely.
Table 3–4.J1: Unregulated Power Input Connector
Terminal Name Function
Tip Positive power supply input
Sleeve Power ground
Table 3–5.J4: External Digital Power Supply Input Connector
Terminal Number Function
1 Digital positive power supply input
2 Digital ground
Table 3–6.J5: External Analog Power Supply Input Connector
Terminal Number Function
1 Analog positive power supply input
2 Analog ground
Connectors
3-7Operation
Table 3–7.BT1: 9-V Battery Connector
Terminal Name Function
Split (female) ring Positive (mates with solid/male post onbattery)
Solid (male) ring Negative (mates with split/female post onbattery)
3.3.4 J2: Analog Inputs
Terminal block J2 is the main analog input to the ADS1254EVM. Two terminalsare provided for each of the ADS1254 four differential inputs. Each terminalis connected to the ADS1254 through a 1-kΩ resistor.
Table 3–8.J2: Analog Inputs
TerminalNumber
TerminalName
ADS1254Pin
Function
1 CH4– 19 Channel 4 negative input
2 CH4+ 20 Channel 4 positive input
3 CH3– 6 Channel 3 negative input
4 CH3+ 5 Channel 3 positive input
5 CH2– 4 Channel 2 negative input
6 CH2+ 3 Channel 2 positive input
7 CH1– 2 Channel 1 negative input
8 CH1+ 1 Channel 1 positive input
3.3.5 J3: External Reference Input
The ADS1254EVM has an onboard 4.096-V bandgap reference. If alower-noise reference source or a reference with a different voltage is desired,it can be connected to screw–terminal block J3. The reference source,onboard or external, is selected using JMP3. Both the onboard and externalreference inputs are filtered and buffered by R2, C3, and U4, and bypassedby C10.
It is also possible to supply a reference voltage directly to the ADS1254 by dis-connecting JMP4 and connecting the reference to pin 2.
Table 3–9.J3: External Reference Input
Terminal Number Function
1 External reference voltage input
2 Analog ground
Connectors
3-8
3.3.6 J8: External Digital Control
Header J8 provides access to certain signals connected between the DSK andthe ADS1254. It can also be used as an additional place to connect externalequipment for communicating with the ADS1254.
Table 3–10.J8: 3.3-V JTAG Port
PinNumber
PinSymbol
SignalName
Direction(at board)
Function
1 NC – – Not connected
3 HOST_CLKXA SERIAL_CLK Input SPI clock for ADS1254
5 HOST_CLKRA HOST_CLKRA Output SPI clock from board; not used
7 HOST_DXA HOST_DXA Output SPI data from board; not used
9 HOST_DRA HOST_DRA Input SPI data for ADS1254 from DSK
11 HOST_FSXA HOST_FSXA Output Frame sync from board; not used
13 HOST_FSRA HOST_FSRA Input Frame sync from DSK; not used
15 HOST_CLKOUT HOST_CLKOUT – Not used
17 HOST_CLKSA HOST_CLKSA – Not used
19 NC – – Not connected
Even-numberedpins
DGND DGND Power Signal ground
3.3.7 J9, J10: DSK Motherboard Connectors
These two connectors are used as both electrical connection and mechanicalsupport for plugging the ADS1254EVM into a DSP DSK. Communicationbetween a DSP on a DSK and the ADS1254 on the EVM is accomplishedthrough these connectors.
J9, the memory interface connector, carries the DSP external bus. J10, theperipheral and control connector, carries various GPIO and peripheral signalsfrom the DSP.
The ADS1254, being a purely SPI part, does not make use of the DSP externalparallel bus; therefore, only one signal connection from J9, a timer output, isused.
J10 carries the DSK serial channels. Texas Instruments DSPs currentlyavailable on DSKs incorporate a multichannel buffered serial port, or McBSP,which among other things supports full-duplex SPI and a frame-sync signal.The ADS1254 has neither of these, so only the McBSPs SPI clock and dataoutputs are connected. The other McBSP signals are brought to J8 forconvenience.
Connectors
3-9Operation
3.3.8 TP1–6: Test Point
The test points are used to monitor certain signals on the board, or to connectexternal signals to the ADS1254.
Consult the ADS1254 data sheet for information on the signals connecteddirectly to the ADS1254.
Table 3–11. TP1–6: Test Points
Test PointDesignator
ADS1254 PinNumber
ADS1254 PinName
Signal Description
TP1 – – Onboard reference voltage
TP2 15 CHS1 Channel Select 1
TP3 16 CHS0 Channel Select 0
TP4 8 ADCLK ADS1254 timing and conversion clock
TP5 13 DOUT SPI data from MCU
TP6 14 SCLK SPI clock
Circuit Description
3-10
3.4 Circuit Description
The ADS1254EVM combines a microcontroller, RAM, and an ADS1254 toprovide a platform for simplified evaluation of the ADS1254.
3.4.1 ADS1254
The ADS1254 (U5) is supported by reference circuitry D1, U4 and associatedcomponents; inputs come from J2 through current–limiting resistors R5–R12.The clock generation circuitry is described below.
For detailed information about the ADS1254, consult the ADS1254 productdata sheet.
3.4.2 Microcontroller
A Texas Instruments MSP430F149 microcontroller (U7), clocked at 8 MHz,provides intelligence for the system. It communicates with the ADS1254 usingone of its two built-in USARTs in synchronous mode, and with the host PCusing the other USART in asynchronous mode. Firmware is stored in andexecuted from the onboard flash memory.
Bulk storage of datapoints collected from the ADS1254 is provided by a128-kilobyte static RAM (U10). It is connected to the MSP430 using 28 GPIOlines.
For detailed information about the MSP430F149, consult the relevantdocumentation, which is available from Texas Instruments website.
3.4.3 Clock Generation
The ADS1254 requires a system clock, from which it derives its sampling rate;the sampling rate is the system clock frequency divided by 384. The systemclock’s maximum specified rate is 8 MHz (maximum sampling frequency is20833 Hz); up to this maximum, virtually any sampling frequency may beselected by generating a clock of the appropriate frequency.
To support a wide range of evaluation situations, the ADS1254EVM has avariable-frequency clock generation system consisting of the MCU, PLL clockgenerator U13, and gate U14. The ICD2053 is a programmable frequencygenerator containing a PLL oscillator and programmable dividers; it is capableof generating frequencies in the 500 kHz–8 MHz range. The reference clockfor the ICD2053 is a buffered version of the MCU main clock, which runs at8 MHz.
Although the ICD2053 adds great flexibility to the ADS1254EVM, its jitter israther high, degrading performance somewhat. The MCU clock source ismuch cleaner. Therefore, those frequencies which can be produced using theMCU are sourced from the MCU instead of the ICD2053. This includes 8 MHz,4 MHz, 2 MHz, and 1 MHz. The choice between the PLL clock and the MCUclock is made by the firmware.
Circuit Description
3-11Operation
3.4.4 Firmware and Host Communication
The ADS1254EVM firmware controls the acquisition of data from theADS1254 and the clock generation circuitry. It is capable of receiving data fromthe ADS1254 at the full data rate, while simultaneously performing averaging.
Communication with the host is performed using TI’s CSR-232 protocol, whichis designed for efficient system control over point-to-point serial links.CSR-232 is based on IEEE P1212r, the control and status registers draftstandard.
The firmware may be upgraded by the user through the serial port. TI mayperiodically make enhancements to the ADS1254EVM firmware; theseupgrades are available on TI’s web site, together with a program for performingthe upgrades.
3.4.5 Power Supply
Power is brought into the board through external power connectors J4 and J5,battery connector BT1, unregulated power input J1, or through the DSKconnectors J9 and J10. If a wall power adaptor is plugged into J1, the batteryis disconnected.
Power supplied from the battery or through J1 is regulated by voltageregulators U1, U12, and U2, which provide 5-V digital and analog supplies, anda 3.3-V digital supply. Power supplied from the external connectors is notfiltered; regulated power of the correct voltages must be supplied to theseconnectors. Power from the DSK is filtered and bypassed. Resistors R15 andR16 limit current in case a DSK is plugged in and the onboard regulators havenot yet shut down.
The board is laid out with separate analog and digital power supplies. Analogpower is 5 V and is supplied from regulator U2, external power connector J5,or the DSK. 3.3-V digital power is supplied from regulator U12 or the DSK.When the external power connector J4 is used, it supplies regulator U12.
Only one component on the board, clock generator U13, uses 5-V digitalpower. When the DSK is used, this component does not operate; however, thisis of no concern, as the DSK supplies its own clock.
Host PC Software
3-12
3.5 Host PC Software
After having installed the software for the ADS1254EVM as described inSection 2.3, you can use it to evaluate the ADS1254. The software is describedin the following subsections.
3.5.1 Main Window
The main window is shown in Figure 3–1. The window is shown as it firstcomes up when the program is started.
Figure 3–1. Main Window
3.5.1.1 Performing an Acquisition
Clicking the acquire button causes an acquisition to begin. Acquisition isperformed in the following sequence:
1) The software configures the ADS1254EVM, telling it what sampling rateto use, how many averages to perform per sample (this is configured inthe Setup window), and how many samples to take.
2) The software instructs the ADS1254EVM to begin sampling.
Host PC Software
3-13Operation
3) The ADS1254EVM begins collecting samples. The ADS1254EVMinforms the software of the progress of the acquisition approximately fourtimes a second; this information is displayed in the status bar at the bottomof the window.
4) The ADS1254EVM tells the software that the acquisition has completed.
5) The software begins reading sample data from the ADS1254EVM. Theread can take some time; the progress of the read operation is indicatedin the status bar.
6) When all of the requested sample data has been read, it is displayed.
3.5.1.2 Acquisition Modes
Two modes of acquisition are available: single shot, and continuous. Themodes are selected using the acquisition mode radio buttons.
In single shot acquisition mode, the program requests one conversion eachtime the acquire button is clicked. In continuous acquisition mode, the programautomatically initiates another conversion when a conversion completes; thisprocess continues until the STOP button is clicked. The STOP button appearswhen an acquisition is started in continuous mode.
3.5.1.3 Sampling Rate
To change the sampling rate, type the desired sampling frequency in hertz inthe sample data rate edit box, and press enter. The program immediatelyrequests that the board change to this sampling rate.
Not all sampling rates are realizable by the board; that is, the clock generatorcircuitry has a finite resolution. The board configures the clock generator sothat it generates the nearest frequency to that requested. It then reports backthe frequency actually being generated. The program replaces the typed-infrequency with the actual frequency being generated by the board, so that youcan always see what the actual sampling frequency is.
Note that the actual frequency of the clock generator is the sampling frequencytimes 384. This adjustment is made by the board.
3.5.1.4 Number of Samples to Acquire
When an acquisition begins, the program requests that the board acquire acertain number of samples. The number of samples to acquire is set using thenumber of samples box. You can type a value in or use the up and downbuttons to select the number of samples to acquire.
Host PC Software
3-14
3.5.2 Display Modes
The evaluation software offers four ways to display sample data:
Scope displays the data as a sample number versus amplitude graph,similar to an oscilloscope
FFT displays a fast Fourier transform of the data on a frequency versusmagnitude graph
Histogram displays the data on a value versus count graph (histogram)
Data list displays the raw sample data in a list
Modes are selected by clicking a tab on the tab bar above the data displayarea, or by selecting an option from the View menu.
The modes are fully described in the following sections.
3.5.2.1 Scope
In scope mode, collected data are displayed as a function of sample number,with the vertical axis measured by code.
You can zoom in on the graph by selecting a rectangular area with the mouse,by clicking and dragging. To zoom out, left-click on the graph and select undozoom from the popup menu that appears; the graph will return to its originalscale.
Left-clicking on the graph brings up a pop–up menu containing numerousdisplay options. Double-clicking with the right mouse button brings up anoptions dialog containing other display options. You can export the graph invarious file formats by selecting export dialog from the popup menu.
3.5.2.2 FFT
In FFT mode, a fast discrete Fourier transform is applied to the dataset, anddisplayed as a graph of frequency in hertz versus magnitude in dB of full scale.A number of options for changing certain parameters of the FFT, such aswindow type and normalization type, are available by clicking the options tab.
You can zoom in on the graph by selecting a rectangular area with the mouse,by clicking and dragging. To zoom out, left-click on the graph and select undozoom from the popup menu that appears; the graph returns to its original scale.
Left-clicking on the graph brings up a popup menu containing numerousdisplay options. Double-clicking with the right mouse button brings up anoptions dialog containing other display options. You can export the graph invarious file formats by selecting export dialog from the popup menu.
Host PC Software
3-15Operation
3.5.2.3 Histogram
In histogram mode, the data are analyzed to see how many times each valueoccurs; this information is shown on a count-versus-value bar graph. Forexample, if the column marked zero shows a bar which is 2 units high, it meansthat two zeros are present in the data. Histograms are useful for analyzingreadings of dc voltages for accuracy.
You can zoom in on the graph by selecting a rectangular area with the mouse,by clicking and dragging. To zoom out, left-click on the graph and select undozoom from the popup menu that appears; the graph returns to its original scale.
Left-clicking on the graph brings up a popup menu containing numerousdisplay options. Double-clicking with the right mouse button brings up anoptions dialog containing other display options. You can export the graph invarious file formats by selecting export dialog from the popup menu.
3.5.2.4 Data List
In data list mode, the data are shown in a list, in order of reception. The datamay be shown in one of four modes:
As integers: Each sample is displayed as a signed base-10 integer. Thesample values are shown exactly as received from the ADS1254.
As hexadecimal integers: Each sample is displayed as an unsignedhexadecimal number. The hexadecimal values are precisely those codesread out from the ADS1254.
As percentage of full scale: The percentage of full scale of each sampleis calculated and displayed.
Scaled by LSB: The voltage measured at each point is calculated anddisplayed.
3.5.3 Setup Dialog
The setup dialog allows you to configure several aspects of the ADS1254EVMsoftware’s operation. It is shown when the program is started, and when theEVM setup option is selected from the edit menu.
Once you are finished making changes in the setup dialog, click the OK buttonto make them effective, or cancel to discard the changes. No changes youmake in the setup dialog take effect before you click the OK button.
Host PC Software
3-16
Figure 3–2. Setup Dialog
3.5.3.1 Serial Port Menu
The serial port menu allows you to choose which serial port to use forcommunication with the ADS1254EVM. The ADS1254EVM must beconnected to the port selected here, or the program will not work.
All of the available ports are shown in the menu. If you know that a port exists,but you do not see it in the menu, it usually means that the port is being usedby another program.
3.5.3.2 Channel to Acquire
The ADS1254EVM can read any of four differential channels. Use the channelto acquire buttons to select which channel to read when performing anacquisition.
By default, this is set to CH1 (channel 1).
3.5.3.3 Reference Voltage
Here you can tell the program what reference voltage you are using. This valueis used in certain display calculations. You must input the correct referencevoltage here, because the board cannot detect the reference voltage, so thesoftware has no way to obtain the information automatically.
Changing the reference voltage here does not affect the operation of theboard; it only changes the reference voltage value used by the program incertain calculations. If the reference voltage selected here is incorrect, somevalues shown by the program will be incorrect, but the program and boardoperate normally otherwise.
Host PC Software
3-17Operation
3.5.3.4 Averaging
The ADS1254EVM board can average together a selectable number ofsamples for each reading. If you want to perform averaging on the data, thiscan drastically reduce the download time, since averaging is performed on theboard, and only the averaged data is downloaded by the host. It also allowsmuch longer readings to be taken, since the board’s RAM is not filled up bysamples which are averaged together; instead, averaging is done before thedata is written into the board’s RAM.
The figure selected here is the number of successive samples that arecollected together and averaged to form one sample. For example, if youselect 32 here, then for each reading, 32 samples are taken and averagedtogether to form that reading. This means that if you request 256 samples tobe acquired, 256 samples are returned, but each sample returned is actually32 successive samples averaged together; so for that acquisition, 8,192samples are taken by the ADS1254.
Note that this changes the effective sampling rate of the returned data.Requesting 32 averages per sample, for example, divides the effectivesampling rate by 32. This is not reflected in the main window; the sampling rateyou select there is always the basic sampling rate, and not the effectivesampling rate after averaging.
The ADS1254EVM can only average samples in quantities which are powersof 2. This dramatically simplifies the averaging calculations that the board’smicrocontroller must perform. The allowable values are all shown in theAveraging menu; up to 32,768 samples per reading can be averaged together.Selecting none from the menu—the default—means that no averages aretaken, and data is returned as read from the ADS1254.
3.5.3.5 Serial Monitor
Checking this box causes the serial monitor window to appear when the setupdialog is closed. This window displays, as it occurs, all serial communicationsbetween the program and the ADS1254EVM, in hexadecimal bytes.
4-1Physical Description
This chapter contains the schematic drawings and PCB layouts for theADS1254EVM board.
Topic Page
4.1 Board Layouts 4-2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2 Schematics 4-4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Chapter 4
Board Layouts
4-2
4.1 Board Layouts
Figure 4–1. Board Layout Top Layer
Board Layouts
4-3Physical Description
Figure 4–2. Board Layout Bottom Layer
Schematics
4-4
4.2 Schematics
The ADS1254 schematics are shown on the following pages.
Schematics
Figure 4-3. Schematic (Sheet 1 of 2)
Physical Description 4-5
12
34
56
ABCD
65
43
21
D C B A
RE
VIS
ION
HIS
TOR
YR
EV
EN
GIN
EE
RIN
G C
HA
NG
E N
UM
BE
RA
PPR
OVE
D
DVCC1
P6.
3/A
32
P6.
4/A
43
P6.
5/A
54
P6.
6/A
65
P6.
7/A
76
VREF+7
XIN8
XOUT/TCLK9
VEREF+10
VREF-/VEREF-11
P1.
0/TA
CLK
12
P1.
1/TA
013
P1.
2/TA
114
P1.
3/TA
215
P1.
4/S
MC
LK16
P1.
5/TA
017
P1.
6/TA
118
P1.
7/TA
219
P2.
0/A
CLK
20
P2.1
/TA
INC
LK21
P2.
2/C
AO
UT/
TA0
22
P2.
3/C
A0/
TA1
23
P2.
4/C
A1/
TA2
24
P2.
5/R
OS
C25
P2.
6/A
DC
12C
LK26
P2.
7/TA
027
P3.
0/S
TE0
28
P3.
1/S
IMO
029
P3.
2/S
OM
I030
P3.
3/U
CLK
031
P3.
4/U
TXD
032
P3.
5/U
RXD
033
P3.
6/U
TXD
134
P3.
7/U
RXD
135
P4.
0/TB
036
P4.
1/TB
137
P4.
2/TB
238
P4.
3/TB
339
P4.
4/TB
440
P4.
5/TB
541
P4.
6/TB
642
P4.
7/TB
CLK
43
P5.
0/S
TE1
44
P5.
1/S
IMO
145
P5.
2/S
OM
I146
P5.
3/U
CLK
147
P5.
4/M
CLK
48
P5.
5/S
MC
LK49
P5.
6/A
CLK
50
P5.
7/TB
OU
TH51
XT2OUT52
XT2IN53
TDO/TDI54
TDI55
TMS56
TCK57
RST/NMI58
P6.
0/A
059
P6.
1/A
160
P6.
2/A
261
AVSS62
DVSS63
AVCC64
U7
MS
P43
0F14
9IP
M
C2+1
GND2
C2-3
V-4
TOU
T15
TOU
T26
TOU
T37
RIN
18
RIN
29
TOU
T410
RIN
311
TOU
T512
FOR
CE
ON
13
FOR
CE
OFF
14IN
VALI
D15
RO
UT1
B16
TIN
517
RO
UT3
18
TIN
419
RO
UT2
20R
OU
T121
TIN
322
TIN
223
TIN
124
C1-25
VCC26
V+27
C1+28U8
MAX3238CPW3.
3Vdd
3.3V
dd
C18
1 uF
C20
1 uF
C15
1 uF
C16
.22
uFC17
1 uF
I/O0
21
I/O1
22
I/O2
23
I/O3
25
I/O4
26
I/O5
27
I/O6
28
I/O7
29
A0
20
A1
19
A2
18
A3
17
A4
16
A5
15
A6
14
A7
13
A8
3
A9
2
A10
31
A11
1
A12
12
A13
4
A14
11
A15
7
A16
10
VDD8
CE
26
CE
130
OE
32
WE
5
GND24
U10
CY6
2128
VLL-
70ZC
3.3V
dd
RA
M_D
0R
AM
_D1
RA
M_D
2R
AM
_D3
RA
M_D
4R
AM
_D5
RA
M_D
6R
AM
_D7
3.3V
dd
RA
M_A
0R
AM
_A1
RA
M_A
2R
AM
_A3
RA
M_A
4R
AM
_A5
RA
M_A
6R
AM
_A7
RA
M_A
8R
AM
_A9
RA
M_A
10R
AM
_A11
RA
M_A
12R
AM
_A13
RA
M_A
14R
AM
_A15
RA
M_A
16
RA
M_A
9R
AM
_A10
RA
M_A
11R
AM
_A12
RA
M_A
13R
AM
_A14
RA
M_A
15R
AM
_A16
C23
10 u
F
C21
10 u
F
RA
M_A
1R
AM
_A2
RA
M_A
3R
AM
_A4
RA
M_A
5R
AM
_A6
RA
M_A
7R
AM
_A8
X1
HC
M49
-8.0
00M
AB
JT
RA
M_C
E
RA
M_O
ER
AM
_WE
RA
M_C
ER
AM
_OE
RA
M_W
E
SP_
TXD
SP_
CTS
SP
_DS
RS
P_D
CD
SP_
RI
SP
_RXD
3.3V
dd
SP_
RTS
3.3V
dd
SP_DTR
SP_
RTS
SP_
TXD
SP_
TXD
SP_
CTS
SP
_DS
R
SP
_DC
D
SP_
RI
SP
_RXD
SP
_RXD
246
1357891011121314
J6 3.3V
JTA
G P
OR
T
RA
M_A
0M
CU
_EN
BL
TCK
3.3V
dd
RE
SE
T#
RE
SE
T#
RD
CTS
DS
RD
CD
RI
TDRTS
DTR
R17
10K
3.3V
dd
RA
M_A
[1..1
6]
1 6 2 7 3 8 4 9 5
DC
D
RD
TD DTR
SG
DS
R
RTS
CTS
RI
J7
7478
44-4
AVd
d
AVd
d
C10
10 u
F
3.3V
dd
C12
1 uF
AVD
D7
CH
1+1
CH
1-2
CH
2+3
CH
2-4
CH
3+5
CH
3-6
CH
4+20
CH
4-19
CH
S1
15
CH
S0
16
AG
ND
17
Vref
18
NC
10
NC
11
DVD
D9
DG
ND
12
CLK
8
SC
LK14
DO
UT
13
U5
AD
S12
54E
R5
1K R6
1K R7
1K R12
1KR8
1K R9
1K R10
1K R11
1K
C3
10 u
F
R2
10K
R1
5.1K
AVd
d
C9
1 uF
J1 PJ-
102B
BT1
9VC
1.1
uFC
4.3
3 uF
C7
10 u
FR
1322
0
C8
10 u
F
D3
SM
L-LX
1206
GC
-TR
D4
SM
L-LX
1206
GC
-TR
R14
390
AVd
d
3.3V
dd
C19
18pF
C14
18pF
SW
1
EVQ
-PJU
04K
6730
SO
UTH
TU
CS
ON
BLV
D.,
TUC
SO
N, A
Z 85
706
US
A
TITL
E
SH
EE
TO
FFI
LE
SIZ
ED
ATE
RE
V4
OC
T 20
01
EN
GIN
EE
R
B
DA
TA A
CQ
UIS
ITIO
N P
RO
DU
CTS
HIG
H P
ER
FOR
MA
NC
E A
NA
LOG
DIV
ISIO
N
R. A
ND
ER
SO
N
B
2
AD
S12
54E
VM
1
C2
.33
uF
12345678
J2 ED
120/
DS
8
DS
P_+
3.3V
DS
P_+
5V
DS
P_G
ND
2 36
7 4
U4
OPA
350E
A
1
2
J3
ED
120/
DS
2
GND3
VIN
5VO
UT
1
EN4
NR2
U1
RE
G10
3-5
C5
10 u
F
GND3
VIN
5VO
UT
1
EN4
NR2
U2
RE
G10
3-5
C6
10 u
F
24
5 3
U11
SN
74LV
C1G
07D
BV
24
5 3
U9
SN
74LV
C1G
07D
BV
1
2
J4 ED
120/
DS
2
1
2
J5 ED
120/
DS
2
R16
10 1
/4W
C11
10 u
F
L1
S18
12-1
04K
DA
TA O
UT
SE
RIA
L C
LK
3.3V
dd
24
53
U3
SN
74LV
C1G
07D
BV
R3
5.1K
3.3V
ddR
45.
1K
R19
10K
3.3V
dd
R21
10K
R23
10K
GR
EE
N
GR
EE
N
100
uH
RS
232
PO
RT
8 M
HZ
RE
SE
T
EXT
VR
EF
1 24
5 3
U6
SN
74LV
C1G
08D
BVR
M. A
SH
TON
PRO
DU
CT
EVA
LUAT
ION
FIX
TUR
ES
CH
EM
ATI
C D
IAG
RA
M
SE
MIC
ON
DU
CTO
R G
RO
UP
R15
10 1
/4W
12
JMP
5M
CU
DIS
AB
LE
CH
1+C
H1-
CH
2+C
H2-
CH
3+C
H3-
CH
4+C
H4-
CHS0CHS1
CH
S0
CH
S1
AD
CLK
RE
FCLK
12
JMP
4R
EF
DIS
CO
NN
EC
T
VREF
123JM
P1
RE
F S
EL
D1
LM40
40A
IM3-
4.1
XTAL
OU
T1
SC
LK2
GN
D3
DA
TA4
CLK
OU
T5
VDD
6
MU
XRE
F/O
E7
XTAL
IN8
U13
ICD
2053
BS
C
5Vdd
AD
CLK
ADCLK
CG
CLK
CG
SD
I
3.3V
dd
C27
1 uF
PLLE
N
C26
56P
F X7
R
3.3V
dd
POS
ITIO
N C
26 A
S C
LOS
ELY
AS
PO
SS
IBLE
TO
U13
NO
TE
UN
LES
S O
THE
RW
ISE
NO
TED
:
ALL
RE
SIS
TOR
S 1
/8W
5%
TH
IN-F
ILM
SU
RFA
CE
MO
UN
T (1
206)
ALL
10U
F C
AP
AC
ITO
RS
PA
NA
SO
NIC
EC
J-3Y
F1A
106Z
OR
EQ
UIV
. (12
06)
ALL
OTH
ER
CA
PAC
ITO
RS
MLC
SU
RFA
CE
MO
UN
T
2 4
15
3 U14SN74LVC1G125DBVR
3.3V
dd
D2
DL4
001
123
JMP
3A
VDD
SE
L
123
JMP
2D
VDD
SE
L
3.3V
dd
C13
1 uF
AD
CLK
VIN
3VO
UT
2
GND1
VOU
T4
U12
RE
G11
17-3
.3
C22
10 u
FC
2410
uF
5Vdd
5Vdd
3.3V
dd
EXT
DIG
ITA
L 5V
IN
+-
+-
DO
CU
ME
NT
CO
NTR
OL
NO
.64
3260
0
EXT
AN
ALO
G 5
V IN
TP1
TP2
TP3
TP4
TP6
TP5
SC
LKD
OU
T
DO
UT
SC
LK
ITE
XAS
NSTRUMENTS
Schematics
Figure 4-4. Schematic (Sheet 2 of 2)
4-6
12
34
56
ABCD
65
43
21
D C B A
HO
ST_C
LKXa
HO
ST_
DXa
HO
ST_
FSXa
HO
ST_
DR
a
12
34
56
78
910
1112
1314
1516
1718
1920
2122
2324
2526
2728
2930
3132
3334
3536
3738
3940
4142
4344
4546
4748
4950
5152
5354
5556
5758
5960
6162
6364
6566
6768
6970
7172
7374
7576
7778
7980
J9
12
34
56
78
910
1112
1314
1516
1718
1920
2122
2324
2526
2728
2930
3132
3334
3536
3738
3940
4142
4344
4546
4748
4950
5152
5354
5556
5758
5960
6162
6364
6566
6768
6970
7172
7374
7576
7778
7980
J10
HO
ST_
CLK
XaH
OS
T_D
XaH
OS
T_FS
Xa
PE
RIP
HE
RA
L / C
ON
TRO
L C
ON
NE
CTO
RM
EM
OR
Y IN
TER
FAC
E C
ON
NE
CTO
R
DSP
_GN
D
HO
ST_
CLK
Sa
12
34
56
78
910
1112
1314
1516
1718
1920
J8
DSP
_+5V
HO
ST_
DR
a
HO
ST_
CLK
Sa
SER
IAL
CLK
HO
ST_
DR
a
HO
ST_
CLK
Xa
DSP
_+3.
3V
MC
U_E
NBL
HO
ST_
FSR
a
HO
ST_
CLK
Ra
6730
SO
UTH
TU
CS
ON
BLV
D.,
TUC
SO
N, A
Z 85
706
US
A
TITL
E
SH
EE
TO
FFI
LE
SIZ
ED
ATE
RE
V4
OC
T 20
01D
OC
UM
EN
T C
ON
TRO
L N
O.
EN
GIN
EE
R
B
DA
TA A
CQ
UIS
ITIO
N P
RO
DU
CTS
HIG
H P
ER
FOR
MA
NC
E A
NA
LOG
DIV
ISIO
NS
EM
ICO
ND
UC
TOR
GR
OU
P
RU
SS
ELL
AN
DE
RS
ON
B
2
AD
S12
54E
VM
2
HO
ST_
CLK
OU
T
DAT
A O
UT
HO
ST_
CLK
OU
T
HO
ST_
CLK
Ra
HO
ST_
FSR
a
ADC
LK
6432
600
MIC
HA
EL
AS
HTO
NPR
OD
UC
T E
VALU
ATIO
N F
IXTU
RE
SC
HE
MA
TIC
DIA
GR
AM
ITE
XAS
NSTRUMENTS
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