Setting the UART3 registers from the M4 core of the iMX7D does not work.

[tamotsu]

Hi.

This is an original circuit board based on the IMX7D-SABRE.

UART3 is controlled by the M4. Changing the register contents will not have any effect.

Writing a value to UART3_UTXD results in an error.

Do I need any special settings to access it from M4?

Best regards.

[Manuel_Salas]

Hello @tamotsu 

I hope you are doing very well.

Are you accessing to the registers from M4?

Did you disable the UART interface in the Device tree Linux?

Best regards,

Salas.

[tamotsu]

Hello Salas.

I debugged u-boot without creating an IVT.
Currently, IVT and u-boot have not been written to memory.

Does this mean I need to configure the M4 to be able to control the UART registers?

If the M4 program is successful, I plan to start debugging it on Linux.

I would appreciate any advice you can give me.

Best regards.

[Manuel_Salas · Accepted solution]

Hello.

It is recommended to follow the chapter 7 Reloading code on i.MX 7Dual/7Solo of the AN5317.

There is explained how to successfully load code from Cortex M and do Heterogeneous processing.

Best regards,

Salas.

[tamotsu]

Hello Salas

I will refer to the application note you provided.

I didn't know there was such a menu when building Linux.

Thank you !!