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Joined: Sat Mar 09, 2019 10:57 pm


Postby nickhaman » Sat May 18, 2019 12:11 am

I am having an issue with a custom board and this module using JTAG. I am connecting to the JTAG pins on the custom board using the JTAG port on the ESP32-WROVER kit with the jumpers removed.

Openocd gives me the following error:
Error: JTAG scan chain interrogation failed: all ones

Upon investigation, it appears that the TMS line is only going to 1V, so JTAG commands aren't being accepted. The TMS line has a direct connection to PIN 13 of the module, with nothing else connected. The module is new with the stock flash.

Is there something in code that is driving that pin low?
If I connect the jumpers on the WROVER kit and try to connect, it succeeds and the voltage goes to 3.3V on TMS. Is there some difference in JTAG operation between the WROVER and the WROOM modules?

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Postby ESP_Sprite » Sat May 18, 2019 8:58 am

Possibly whatever is in flash has reconfigured those I/O ports to something else than JTAG. Suggest you flash some known-good stuff over serial to the ESP32 first.

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