The cs pin of the spi is not working

RE: The cs pin of the spi is not working

emmovo — Fri, 15 Mar 2024 01:37:52 GMT

My problem has been solved. As you said, after I mounted the spi with a special device in the device tree, the cs works fine. Thank you for your patient, professional and efficient technical support!

RE: The cs pin of the spi is not working

Vidar Berg — Thu, 14 Mar 2024 13:07:17 GMT

Yes, correct. That is what I would expect, at least. I've never tried to use the SPI node without specifying a bus device in the DT.

RE: The cs pin of the spi is not working

emmovo — Thu, 14 Mar 2024 13:03:52 GMT

Thanks for the reminder, what you mean is that I need to mount a specific device under the spi node of the device tree for the cs to be assigned and thus have the appropriate slice selection action; if I simply configure the spi without a specific device, the cs won't have an action; am I understanding this correctly?

RE: The cs pin of the spi is not working

Vidar Berg — Thu, 14 Mar 2024 12:43:20 GMT

I believe the problem in your case is that you have not specified any devices on your SPI bus, so the CS pin is not assigned to any device.

Here is an example which use the SPI API directly:

https://github.com/too1/ncs-spi-master-slave-example/tree/master

Notice that it defines a bus device in the overlay here: https://github.com/too1/ncs-spi-master-slave-example/blob/629db4cf8000605ddf46a5ac18936552bae3f52f/boards/nrf52840dk_nrf52840.overlay#L46

RE: The cs pin of the spi is not working

emmovo — Thu, 14 Mar 2024 12:26:00 GMT

Thank you very much for your reminder, I already know that I can directly add the st7789v node through the device tree in order to achieve the driver display, and successfully complete the display function; however, I still want to know the reason why I used the spi way cs signal line above did not work properly; I worry that if I face other zephyr device tree later when there is no preset device, I don't know how to deal with it; I hope to get your support. I hope I can get your support, thanks!

RE: The cs pin of the spi is not working

Vidar Berg — Thu, 14 Mar 2024 12:16:50 GMT

Hello,

If you search for 'st7789v' in the SDK, you should find multiple references to how the device can be defined in the devicetree. There's also the Generic ST7789V Display Shield you can use.

Best regards,

Vidar