Flashing custom hardware with IMX8MPLUS processer using JTAG

[dylanrd]

Hi,

I am using a custom board that uses the IMX8MPLUS processor. Currently, the processor has no firmware or bootloader installed on it. 

Is it possible to flash a simple bootloader using the JLink debugger onto the processor using the JTAG connection? I have been trying to connect the debugger onto our board but I cannot connect to it. Getting errors such as Low voltage, or Reset pin is high.

Surely there should be a way to flash a simple bootloader using just the JTAG before anything is installed, without having to use the USB serial downloader?

Thanks in advance

[Sunil_13]

Hi,

I have some questions regarding JTAG connectivity and boot options for a custom i.MX8M Plus board.

1. How do you typically connect your board for debugging — using JTAG or another interface?

   • If JTAG is used, do you connect after U-Boot has executed or before boot (at power-on reset)?

2. In our custom board, USB and SD interfaces are not populated, so we currently have only JTAG available for communication and detection.

   • Could you please advise on the correct procedure or configuration to bring up the board only via JTAG ( DSTREAM-ST)?

   • Is there any additional configuration needed in the SJC / JTAG_MOD / Boot_Mode pins for enabling debug access when no boot device is present?

[Manuel_Salas]

Hello @dylanrd 

I hope you are doing very well.

It should be possible to at least flash the bootloader to i.MX8MP, but unfortunately we have not any script example with the memory map and process to achieve it. NXP supports and recommend to use the UUU tool (USB Serial Download).

When customer wants avoid to use the USB Serial Download, it is recommended to contact to the chip vendor (eMMC vendor) to get it with a flashed image.

About of Low voltage and Reset pin issues, it is possible you have hardware issues. You can refer to the Schematics of the i.MX8MP to compare the JTAG connector and if possible test with an EVK.

Best regards,

Salas.

[dylanrd]

Hi @Manuel_Salas 

Thank you for your answer, tgat makes sense. In the Hardware guide for the IMX8MP processor, it states that we need to do a JTAG connectivity test. I thought that would require flashing the bootloader and connecting to the debug part of the CPU, as I tried to do here. Have I maybe misunderstood what is meant by testing JTAG connectivity, and is there another way to do it?

[Manuel_Salas]

Hello @dylanrd 

You can check the JTAG functionality trying to debug an application.

As example, you can refer to the AN14367 and the AN14120.

Both are detailed instructions to debug Cortex A and Cortex M.

Best regards,

Salas.