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Signal Capture for debug

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hasu@tmk edited this page May 19, 2022 · 28 revisions

WORK_IN_PROGRESS

This is not that useful if you have already logic analyzer or oscilloscope. This can be used by users who don't have the equipments to see signal of their keyboard.

There are converter firmwares with Signal Capture enabled.

https://github.com/tmk/tmk_keyboard/tree/signal_capture/converter/ibmpc_usb

https://github.com/tmk/tmk_keyboard/tree/signal_capture/converter/pc98_usb

make -f Makefile.capture

Capture record

Signal Capture prints signal data in text format on hid_listen like below.

0021 0001 0001 6401 D423 D5C2 D720 D962 DBD0 DE22 DF53 E091 E2E3 E402

Convert into VCD format

Capture records need to be convertered into Value Change Dump(VCD) format using tmk_core/common/capture2vcd.py to see signal.

$ python3 capture2vcd.py <capture_file>

or

$ cat <capture_data> | python3 capture2vcd.py

You can see converted VCD data with tool like sigrok PulsView.

Internals

Capture record format

Captured data are stored in ring buffer at AVR SRAM(0x100-2FF) temporarily and then, printed in format below.

    # Pin change:
    #     TTTP
    # Timer overflow:
    #     CC0P
    # P:Pin(4bit)
    # T:Timer(12bit)[us]
    # C:Overflow count(8bit)

Sigrok

https://sigrok.org/wiki/Main_Page

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