MIPI DevCon 2016: Versatile Software Solution for MIPI C-PHY TX Testing
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The document describes a software tool called CPHYGUI that was developed by UNH-IOL to test the transmitter (TX) functionality of the MIPI C-PHY specification. The tool allows users to capture waveform data from an oscilloscope, decode packet information, and perform measurements to test TX parameters like timing, voltage levels, and signal quality. It provides a graphical interface and command line access to automate compliance testing and save results.
MIPI DevCon 2016: Versatile Software Solution for MIPI C-PHY TX Testing
- 1. Versatile Software Solution for MIPI C-PHY TX Testing Paul Willis UNH-IOL
- 2. 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 2
- 3. 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 3
- 4. 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 4
- 5. 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 5
- 6. CPHYGUI 6
- 7. Test Setup 7 • 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) Probing Point C-PHY RTB Oscilloscope Computer CPHYGUI Da A/B/C Da A/B/C Ch 1/2/3 Da A/B/C GPIB / Ethernet
- 8. 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 8
- 9. 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 9
- 10. 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: 10
- 11. 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 11
- 12. 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 12
- 13. VOHHS • Mean of single ended waveform taken at -20% of UI • Applicable to all 3 single ended lines 13
- 15. T3-POST • Verify that the last 7 symbols in the burst are the “4” symbol 15