Today I received my Jlink OB, to try to Program/Debug the RT1020 microcontroller directly, without using OpenSDA/Daplink that installs the evaluation board.
I have removed the jumpers that connect SWDIO and SDCLK to OpenSDA (J27--> SWDIO, J28--> SWCLK ), and I have connected those signals and GND to the Jlink OB. MCUXpresso recognizes the Jlink, but fails to connect to the microcontroller.
There are three more jumpers in the evaluation board (J24, J25 and J26), two are for a UART and one for the RST signal. If I remove these jumpers, and use OpenSDA-DAP Link via USB or JTAG work well, it seems that the UART is not useful to program and debug, I do not know what is the utility of this serial port, but it is not essential for debugging or program.
I also tried to connect my Jlink V9 by SWD directly to the RT1020 and it also fails. I do not understand why I can not connect directly to the RT1020 microcontroller by SWD using a Jlink, when the OpeSDA (based on Kinetis MK20) on the evaluation board is also connected via SWD to the microcontroller.
It seems that OpenSDA sends some special commands by SWD to the microcontroller, but if it connects directly with Jlink it does not do it, or so it seems. I need to be able to program and do Debug, using SWD directly, without OpenSDA as an intermediary, to make my own board.