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RA8875 Shield with SAMD21 - Library SERCOM change
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RA8875 Shield with SAMD21 - Library SERCOM change

by Linux_69 on Thu May 13, 2021 7:42 am

Hi folks,
I'm new here and hope I do it correctly.
I purchased the RA8875 interface with the 7" TFT Display and all works fine with the 328 arduino UNO.
I saw that this interface works with the SAMD21 (Metro M0 Express), too. I have now a special board (www.briki.org) with two processors: a SAMD21 and a ESP32.
My problem is that this board has an internal communication interface between the SAMD21 and the ESP32 through the SERCOM1 and this is not available for external use.
Now I know that the SAMD21 has 6 SERCOM and the RA8875 library works on hardware SPI only, but I can't find where I have to change the SERCOM.
My question is now how can I set the RA8875 library to work with one of the other hardware SERCOM of the SAMD21. Could me please help? Thank you in advance for your help.

Linux_69
 
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Re: RA8875 Shield with SAMD21 - Library SERCOM change

by adafruit_support_mike on Fri May 14, 2021 1:19 am

This tutorial shows how to configure SERCOMs on a SAMD21:

https://learn.adafruit.com/using-atsamd ... rial-ports

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Re: RA8875 Shield with SAMD21 - Library SERCOM change

by Linux_69 on Fri May 14, 2021 1:35 pm

Thank you very much for your link.
In the meantime all works fine. The briki.org support told me that your library RA8875 use spi.h. One has just to download the briki configuration files for the arduino IDE and then it will be possible to use the SPI "out of the box" without any manual operations.
One should change the “CS” connection on pin 13 (instead of 10 as in the demo program) because this pin is already configured into the spi.h (briki.org) as 13.
One should just change it in the demo program definitions (#define RA8875_CS 13) and physical connect the "CS" wire on pin 13 (ABC board with briki module).
The other pins are: pin 23 (MOSI), pin 25 (MISO) and pin 24 (SKC) of the ABC Board. Connecting these pins with the same pin signals of the RA8875 board and that is!
The signals RST and INT can be user defined.
On the following picture you can see the SPI interface pins.
ABC-SPI.png
SPI pin connections
ABC-SPI.png (247.13 KiB) Viewed 209 times

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Re: RA8875 Shield with SAMD21 - Library SERCOM change

by adafruit_support_mike on Fri May 14, 2021 9:43 pm

Glad to hear you have it working. Happy hacking!

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Please be positive and constructive with your questions and comments.