Using JTAG with CMSIS-DAP

Development Boards MicroMod
1

I am attempting to connect to a TWR-LS1021A dev board through the built-in CMSIS-DAP debugger. From the schematics I can see that it connects to the LS1021A through JTAG not SWD. When I attempt to connect with OpenOCD I get the following result:

openocd.exe -c "interface cmsis-dap"
Open On-Chip Debugger 0.9.0 (2015-05-19-12:09)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : only one transport option; autoselect 'swd'
Info : CMSIS-DAP: JTAG Supported
Error: CMSIS-DAP: SWD not supported

When I unplug the USB to the dev board I get this:

openocd.exe -c "interface cmsis-dap"
Open On-Chip Debugger 0.9.0 (2015-05-19-12:09)
Licensed under GNU GPL v2
For bug reports, read
        http://openocd.org/doc/doxygen/bugs.html
Info : only one transport option; autoselect 'swd'
Error: unable to find CMSIS-DAP device

This seems to indicate that OpenOCD recognizes the attached debugger, but is attempting to use it as a SWD connection not a JTAG connection. How do I get it to attempt to use it as JTAG?

2

In looking into this more, it appears that OpenOCD only support SWD over CMSIS-DAP. What is the effort involved in adding support for JTAG over CMSIS-DAP?

3

Check out the IDAP-Link from here http://embeddedsoftdev.blogspot.ca/p/idap-link.html. It’s a full CMSIS-DAP jtag and works very well with OpenOCD. Tested with Nordic nRF5x, NXP LPC series, Freescale KL.

4

hi, diltsman. I meet the same question with you.

There are 2 things we had to do to add support for JTAG over CMSIS-DAP:

  1. modify the code of /src/jtag/drivers/cmsis_dap_usb.c，make it support for JTAG.

  2. modify the CMSIS-DAP firmware running on the adapter, make it support for JTAG.

I had done the 2, but I have no idea with 1, have you come out this?

5

With the IDAP-Link supports both mode SWD & JTAG, nothing to modify. See http://embeddedsoftdev.blogspot.ca/p/idap-link.html