Versatile Software Solution

for MIPI C-PHY TX Testing

Paul Willis UNH-IOL

Contents • Who is the UNH-IOL? •  C-PHY TX Testing Tool Overview •  Physical Test Setup •  Clock and Data Recovery •  HS Packet Decode •  HS TX tests

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UNH-IOL • MIPI Member since 2007 • Helped develop D-PHY Test Suite • Authored DPHYGUI Test Tool • Active test house for MIPI CSI, MIPI DSI,

and MIPI D-PHY • Active in the Test Work Group • Work with several other Organizations to

develop new technologies • Employ 100 university students

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Testing MIPI C-PHY TX

• Address issue of missing reference platform for performing C-PHY CTS TX tests

• The industry has need for this software • Will be available for purchase to MIPI

members • Meant to complement oscilloscope

software package offerings

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CPHYGUI Overview • MATLAB based software measurement tool • Evaluate PHY TX characteristics • Capture, import, and process waveforms

•  Can download captures or import saved waveform files from Tektronix, Keysight, LeCroy, and Rhode & Schwarz oscilloscopes

• Decode HS packets and LP sequences • Display and manage measurement results in GUI • Load/save measurement results • Command Line Interface

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CPHYGUI

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Test Setup

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•  Real time oscilloscope •  High impedance probes

•  C-PHY Reference Termination Board •  RTB may be used as probing point with probe tips soldered to the board

DUT(P339)

ProbingPoint

C-PHYRTB

OscilloscopeComputerCPHYGUI

DaA/B/C DaA/B/C

Ch1/2/3DaA/B/C

GPIB/Ethernet

Clock and Data Recovery •  Lowpass filter data •  Find differential edge times •  Throw out edges from out of spec UI (too long/short) •  Find mode of UI length •  Run second pass using previously estimated UI length

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Decoder •  Byte level decode of HS burst packets

•  Protocol aware (CSI-2 and DSI) planned

•  LP decoder planned • Output to console • Option to save log to text file

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HS-TX Tests •  Capture from oscilloscope or import from file

•  Sample rate above 5 GS/s and burst length of at least 5 thousand symbols suggested.

•  Cropped single burst:

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TLPX, T3-PREPARE, T3-PREAMBLE, and T3-SYNC

•  HS entry timers measured as described in CTS •  TLPX: Time between VA and VC crossing VIL,MAX (550 mV). •  T3-PREPARE: Time between end of TLPX and HS-0 (+/- 40 mV). •  T3-PREAMBLE: Verifies length of preamble (in place of following tests). •  T3-PREBEGIN/T3-PROGSEQ/T3-PREEND: To be implemented. •  T3-SYNC: verify sync word (3,4,4,4,4,4,4,3) after preamble

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VOD (max strong, min weak HS-0 and HS-1) •  Eye based measurements performed on all three

differential pairs (VOD-AB, VOD-BC, VOD-CA) • Measured at -20% of UI •  Calculate ΔVOD by subtracting absolute value of

maximum strong 1 from absolute value of strong 0. •  Take highest value from all three differential pairs

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VOHHS • Mean of single ended waveform taken at -20% of UI •  Applicable to all 3 single ended lines

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VCPTX and ΔVCPTX(HS) • 

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T3-POST •  Verify that the last 7 symbols in the burst are the “4”

symbol

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