JTAGenum is a tool can be used with a Raspberry PI or an Arduino to find to try JTAG pins from an unknown chip. In the Arduino, connect the pins from 2 to 11 to 10pins potentially belonging to a JTAG. Load the program in the Arduino and it will try to bruteforce all the pins to find if any pins belongs to JTAG and which one is each. In the Raspberry PI you can only use pins from 1 to 6 (6pins, so you will go slower testing each potential JTAG pin).
In Arduino, after connecting the cables (pin 2 to 11 to JTAG pins and Arduino GND to the baseboard GND), load the JTAGenum program in Arduino and in the Serial Monitor send a
h(command for help) and you should see the help:
Configure "No line ending" and 115200baud. Send the command s to start scanning:
If you are contacting a JTAG, you will find one or several lines starting by FOUND! indicating the pins of JTAG.