JTAG vs SWD with MCUXpresso and Kinetis K22.
I have a new PCB with a K22FN512VDC12. I can connect to the part with a PE Micro Multilink Universal using SWD mode. All is fine.
One of the SW developers claims he could Debug in JTAG mode on another K22 board, but if I uncheck the SWD select box in the config for the Multilink with this board it fails to connect to the target. I am running the latest MCUXpresso version and just loaded the latest driver from PE Micro. Physical interface is just straight short wires between the CPU and the JTAG conn.
I am honestly not concerned but before I go too far down this hole I want to understand if this SHOULD work or not. Is there something special config wise to enable JTAG mode operation?
OK, mystery solved. I have some bad boards. TDO was disconnected on the sample PCB that was delivered to me. Perfectly explains why SWD works and JTAG doesn't! Appreciate the comments.
Yes I do have the full JTAG interface connected. I am really just looking to confirm if this should work. Ideally someone who has connected to a K22 in JTAG mode with a PE Micro Multilink can con confirm this.
There is the possibility that I have an issue on the PCB with those two extra lines that JTAG requires, but I was wondering if there was anything else you had to do configuration wise to go from SWD to JTAG.
Yes, I have used the K22 in JTAG mode. One thing to consider is to have the pins configured for JTAG mode (Processor Expert setting below).
The other thing is to make sure that the traces are not subject to noise.
I hope this helps,
For SWD, you need DIO and DCLK, while for JTAG you need 4 pins (TMS, TCK, TDO and TDI).
So for using JTAG, you need these pins available and connected to the debug header.
There is a discussion on this at Using the FRDM-K64F with CodeWarrior | MCU on Eclipse
I hope that helps,