Jtag invalid acknowledgment

Question

I'm using OpenOCD on a ARM9 with the sysfsgpio bitbang interface, and try to debug a Cortex M3 stm32f103 microcontroller. The OS used is an embedded debian. Unfortunately after getting the device id I keep getting a wrong ACK from the target (Warning, invalid ACK 0x4 in jtag DP transaction).

Do you have any insights on what could be the cause of the problem? I plotted every signals on an oscilloscope and didn't see anything wrong, I also checked the target device with an olimex jtag-key and it is working.

Answer 1

There was a wrong contact between the microcontroller and the JTAG connector on the TDI line, however the target device was sending its ID since it doesn't require a specific instruction...