MICROCONTROLLERUSART

anang.tj@pens.ac.id

POLITEKNIK ELEKTRONIKA NEGERI SURABAYAPROGRAM STUDI ELEKTRO INDUSTRI

DEPARTEMEN TEKNIK ELEKTRO

Microcontroller D-III ELEKTRO INDUSTRI

Remote Monitoring

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KonverterTTL-RS232

KonverterUSB-RS232

MCU

PLANT

PC

Sarana Transmisi(wire, wireless, optik

Microcontroller D-III ELEKTRO INDUSTRI

Convert to RS-232

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Microcontroller D-III ELEKTRO INDUSTRI

Device with RS-232 Port

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Microcontroller D-III ELEKTRO INDUSTRI

Feature USART

Full Duplex Operation (Independent Serial Receive and Transmit Registers)

Asynchronous or Synchronous Operation

Master or Slave Clocked Synchronous Operation

High Resolution Baud Rate Generator

Supports Serial Frames with 5, 6, 7, 8, or 9 Data Bits and 1 or 2 Stop Bits

Odd or Even Parity Generation and Parity Check Supported by Hardware

Data OverRun Detection

Framing Error Detection

Noise Filtering Includes False Start Bit Detection and Digital Low Pass Filter

Three Separate Interrupts on TX Complete, TX Data Register Empty, and RX Complete

Multi-processor Communication Mode

Double Speed Asynchronous Communication Mode

The ATmega128A has two USARTs, USART0 and USART1

Microcontroller D-III ELEKTRO INDUSTRI

Block Diagram

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DATA

DATA

Other Device

Microcontroller D-III ELEKTRO INDUSTRI

Direction and Flow of Data

TTL Level from MCU

FLOW/DIRECTION OF DATA/bit

Microcontroller D-III ELEKTRO INDUSTRI

RS-232 Level

Microcontroller D-III ELEKTRO INDUSTRI

Pin-out RS-232

Converter TTL-RS232

TTLRS-232

Microcontroller D-III ELEKTRO INDUSTRI

Wiring Connection of RS-232

Microcontroller D-III ELEKTRO INDUSTRI

Wiring Connection Alternative

Microcontroller D-III ELEKTRO INDUSTRI

Format Frame of Data

1 start bit 5, 6, 7, 8, or 9 data bits no, even or odd parity bit 1 or 2 stop bits

Microcontroller D-III ELEKTRO INDUSTRI 13

Microcontroller D-III ELEKTRO INDUSTRI

Send DATA A

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ASCII A= 100 0001B

Data length : 7 bitParity : ODDStop bit : 1 0100000111

Arah pengiriman data

START BIT

DATA PARITY

BITSTOP BIT

Microcontroller D-III ELEKTRO INDUSTRI

Error Check

A single bit is appended to each data chunkmakes the number of 1 bits even/odd

Example: even parity1000000(1)

1111101(0)

1001001(1)

Example: odd parity1000000(0)

1111101(1)

1001001(0)

Peven Parity bit using even parity

Podd Parity bit using odd paritydn Data bit n of the character

Microcontroller D-III ELEKTRO INDUSTRI

Parity Generators

Microcontroller D-III ELEKTRO INDUSTRI

Parity Checker

Microcontroller D-III ELEKTRO INDUSTRI

Register

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Microcontroller D-III ELEKTRO INDUSTRI

UCSRnA Register

Bit 7 RXCn: USART Receive Complete

This flag bit is set when there are unread data in the receive buffer and

cleared when the receive buffer is empty (that is, does not contain any

unread data). If the receiver is disabled, the receive buffer will be flushed and

consequently the RXCn bit will become zero. The RXCn flag can be used to

generate a Receive Complete interrupt.

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Bit 6 TXCn: USART Transmit Complete

This flag bit is set when the entire frame in the Transmit Shift Register has been

shifted out and there are no new data currently present in the transmit buffer (UDRn).

The TXCn flag bit is automatically cleared when a transmit complete interrupt is

executed, or it can be cleared by writing a one to its bit location. The TXCn flag can

generate a Transmit Complete interrupt (see description of the TXCIEn bit).

Microcontroller D-III ELEKTRO INDUSTRI

UCSRnA Register

Bit 5 UDREn: USART Data Register EmptyThe UDREn flag indicates if the transmit buffer (UDRn) is ready to receive new data. If UDREn isone, the buffer is empty, and therefore ready to be written. The UDREnflag can generate a DataRegister Empty interrupt (see description of the UDRIEn bit).UDREn is set after a reset to indicate that the Transmitter is ready.

Bit 4 FEn: Frame ErrorThis bit is set if the next character in the receive buffer had a Frame Error when received, that is,when the first stop bit of the next character in the receive buffer is zero. This bit is valid until thereceive buffer (UDRn) is read. The FEn bit is zero when the stop bit of received data is one.Always set this bit to zero when writing to UCSRnA.

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Microcontroller D-III ELEKTRO INDUSTRI

UCSRnA Register

Bit 3 DORn: Data OverRunThis bit is set if a Data OverRun condition is detected. A data overrun occurs when the receivebuffer is full (two characters), it is a new character waiting in the Receive Shift Register, and anew start bit is detected. This bit is valid until the receive buffer (UDRn) is read. Always set thisbit to zero when writing to UCSRnA.

Bit 2 UPEn: Parity ErrorThis bit is set if the next character in the receive buffer had a Parity Error when received and theparity checking was enabled at that point (UPMn1 = 1). This bit is valid until the receive buffer(UDRn) is read. Always set this bit to zero when writing to UCSRnA.

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Microcontroller D-III ELEKTRO INDUSTRI

UCSRnA Register

Bit 1 U2Xn: Double the USART Transmission SpeedThis bit only has effect for the asynchronous operation. Write this bit to zero when using synchronousoperation.Writing this bit to one will reduce the divisor of the baud rate divider from 16 to 8 effectively doublingthe transfer rate for asynchronous communication.

Bit 0 MPCMn: Multi-Processor Communication ModeThis bit enables the Multi-processor Communication mode. When the MPCMn bit is written toone, all the incoming frames received by the USART Receiver that do not contain address informationwill be ignored. The transmitter is unaffected by the MPCMnsetting.

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Microcontroller D-III ELEKTRO INDUSTRI

USART Setup

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// USART0 initialization// Communication Parameters: 8 Data, 1 Stop, No Parity// USART0 Receiver: On// USART0 Transmitter: On// USART0 Mode: Asynchronous// USART0 Baud Rate: 9600UCSR0A=0x00;UCSR0B=0x98;UCSR0C=0x06;UBRR0H=0x00;UBRR0L=0x33;

Microcontroller D-III ELEKTRO INDUSTRI

USART with Interrupt

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interrupt [USART0_RXC] void usart0_rx_isr(void){char status,data;status=UCSR0A;data=UDR0;if ((status & (FRAMING_ERROR | PARITY_ERROR | DATA_OVERRUN))==0)

{rx_buffer0[rx_wr_index0++]=data;

#if RX_BUFFER_SIZE0 == 256// special case for receiver buffer size=256if (++rx_counter0 == 0) rx_buffer_overflow0=1;

#elseif (rx_wr_index0 == RX_BUFFER_SIZE0) rx_wr_index0=0;if (++rx_counter0 == RX_BUFFER_SIZE0)

{rx_counter0=0;rx_buffer_overflow0=1;}

#endif}

}

Microcontroller D-III ELEKTRO INDUSTRI

Instruction on C Microcontroller

The serial communication is realized using the Standard Input/Output Functions getchar, gets, scanf, putchar, puts and printf.The UART0 (USART0) will use the normal putcharand getchar functions.In case of interrupt driven buffered communication, UART0 (USART0) will use the following variables:

rx_buffer0, rx_wr_index0, rx_rd_index0, rx_counter0, rx_buffer_overflow0,tx_buffer0, tx_wr_index0, tx_rd_index0, tx_counter0.

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Microcontroller D-III ELEKTRO INDUSTRI

Source Code C-Code Vision(examp)

Receive character from PC

Display on LCD

Send Character to PC

char data;While(1){

data=getchar();lcd_gotoxy(0,0);lcd_putchar(data);putchar(data);

}

adc_CH4=read_adc(4);hasil=(float)adc_CH4;hasil=hasil/5;sprintf(buff,"%2.3f ",hasil);lcd_gotoxy(0,0);lcd_puts(buff);printf("%2.3f",hasil);delay_ms(3000);

Read from ADC ch4 in hasil

Display on LCD

Send hasil to PC

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Microcontroller D-III ELEKTRO INDUSTRI

Circuit on MCU

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Microcontroller D-III ELEKTRO INDUSTRI

Source Code on MCU

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while (1){tegangan=(float)read_adc(0)*250/1023;arus=(float)read_adc(1)*10/1023;lcd_gotoxy(1,0);lcd_putsf(" TELEMETRY ");lcd_gotoxy(0,1);lcd_putsf("TEGANGAN: ");lcd_gotoxy(0,2);lcd_putsf("ARUS : ");lcd_gotoxy(9,1);sprintf(buff,"%3.2f",tegangan);lcd_puts(buff);lcd_gotoxy(9,2);sprintf(buff,"%3.2f",arus);lcd_puts(buff); printf("%3.2f%3.2f\r",tegangan,arus);delay_ms(100);

}

float tegangan,arus;unsigned char buff[20];

Microcontroller D-III ELEKTRO INDUSTRI

Display on PC

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Microcontroller D-III ELEKTRO INDUSTRI

Source Code on PC

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Dim data As StringDim tegangan, arus As Variant

Private Sub Command1_Click()If rs232.PortOpen = False Then rs232.PortOpen = TrueEnd Sub

Private Sub Command2_Click()If rs232.PortOpen = True Then rs232.PortOpen = FalseEnd Sub

Private Sub Command3_Click()If rs232.PortOpen = True Then rs232.PortOpen = FalseUnload MeEnd Sub

Private Sub rs232_OnComm()data = data + rs232.InputIf InStr(data, vbCr) ThenText2.Text = Mid$(data, 1, 6)Text3.Text = Mid$(data, 7, 6)tegangan = Val(Text2.Text)arus = Val(Text3.Text)data = ""End If

End Sub

Private Sub Timer1_Timer()If tegangan >= 230 ThenShape1.FillColor = vbRedElseShape1.FillColor = vbGreenEnd IfEnd Sub

Private Sub Form_Load()With rs232.Settings = "9600,n,8,1".RThreshold = 1.InputLen = 1.CommPort = Text1.TextEnd WithEnd Sub