2016-02-17 07:44 AM
I built my own board and I am trying to use the JTAG connections. It does not seem to work. It only uploads a small percentage of time and even when it does, I am not to sure it is uploading correctly. I thought it was the reset circuit, because on the small amount of times I wanted to upload, I need to power cycle the board in order for the code to take action. I just tried SWD by random luck. It works really well. So, the question is, why does SWD work and not JTAG? With SWD, when code uploads, I do not have to power cycle the board. When I select JTAG in TrueStudio, are they expecting the 20 pin JTAG? I am kind of dumbfounded as to why one works well and the other does not. Also, under JTAG, in order to upload code, I have to do a core reset. If I try a hardware reset, it does not work at all.
2016-02-17 09:09 AM
The 20-pin header is just a connector, the active pins a subset of the total. Here we have JTAG and SWD functional with the 10-pin header configuration ARM has migrated too.
Perhaps you have issues with the pull-up/down configuration or wiring, it is really hard to surmise from the prose.2016-02-17 10:23 AM
2016-02-17 12:38 PM
Here is a dumb question. Is JTAG reset also supposed to go to the system reset pin?
2016-02-17 01:00 PM
NRST != NJTRST (PB4)
2016-02-17 01:32 PM