#garfield Logs

Jun 22 2023

01:00 PM polprog: rue_mohr: using openocd and a list of GPIO configs, but it is not working on all boards I want it to work
01:10 PM polprog: so i did not post it yet
02:51 PM polprog: https://polprog.net/rozne1/ircjunk/scan_jtag.sh
02:52 PM polprog: rue_mohr: ^ theres the script - it now works on the target board
02:52 PM polprog: and i learnt that nRESET != TRST
02:52 PM polprog: basically you take the first 4 gpio pins on a raspberry pi, or whatever else that supports sysfs gpio
02:53 PM polprog: and the script will run openocd for each combination of the TMS TCK TDI TDO pins (there are 24 of them)
02:53 PM polprog: and if a TAP is found by openocd it will report the matching pin config and quit
02:54 PM polprog: so this is used to find the jtag pinout of an unknown device. Worst case scenario is that you will have to run it 4 times to guess the trst pin
02:57 PM polprog: for now you have to know the trst pin, but if you really wanted you could also brute that
02:57 PM polprog: then you have 5! combinations to test
02:58 PM polprog: 4! if you instead guess the TDO pin
02:58 PM polprog: But at that point I would rewrite it in something else than bash, this is hacked together anyway
06:12 PM rue_mohr: hi
06:13 PM rue_mohr: openocd cant do that?
06:14 PM rue_mohr: you have to tell openocd everything and even then it might not work
06:14 PM rue_mohr: I wans trying to get it to just verify a shift chain. Useless
09:21 PM Tom_L: sub imploded
11:04 PM rue_mohr: yea
11:04 PM rue_mohr: I thought it had
11:04 PM rue_mohr: no images of anything tho
11:04 PM rue_mohr: what was the article a distraction from
11:04 PM rue_mohr: sinking immigrants ship?
11:08 PM rue_mohr: ah, in grece