6 years, 10 months ago.

The Nucleo board of course has an STLink V2.1 built in that will work with IAR's IDE for debugging including breakpoints, watch variables, etc. This is by far the easiest way to do debugging and is one of the main reasons for buying a Nucleo board. Just plug in the one USB cable to your PC, ensure the right driver is installed and you are good to go. IAR should work fine with the STLink.

Theoretically it is possible to use an external Jlink to do debugging, but will be tricky. I believe SWD is generally replacing full Jtag these days due to requiring much fewer pins on the target. If the Jlink is relatively new it should support SWD mode as well. Conceptually the connection is straight forward. The debugger needs the Clock pin on the micro and the Data pin on the micro, and the Reset pin on the micro. Check the micro data sheet, these pins should be clearly marked.

The Jlink will also need access to the target Vdd to and target ground. The debugger does not necessarily provide power to the target, so you will have to provide external power to the board. You will have to check the specs for your Jlink and see if one of the pins is meant to source voltage to the target. You will also have to read the manual for your Nucleo board and see how the onboard mbed interface is connected to the target. You may have to move some jumpers or even cut traces so the mbed interface does not interfere with the external jlink.

Need to think about the Oscillator as well, as the target is clocked from the mbed interface IC. But it should roll over to internal RC by default though or you can add the external crystal.

And of course the Nucleo does not have the standard 20pin Jtag header, so you will have to figure out how to jumper the connections from the Jlink to the Nucleo board.

Which is a long way of saying, getting by with the onboard ST Link would be a lot easier.