NanoPi R2S - GPIO - UART1: Enabled by default ?

[Willena]

Hello everyone.

 

I'm using the latest version of armbian for the NanoPi R2S. I noticed that the board has 4 exposed GPIO ports on the board.

I'm interested in using the RX1 and TX1 and use it for the UART interface.

 

It seems I cannot use it. It might be disabled by default. Can somebody confirm or not if UART1 is enabled by default and if not what should I do to enable it ?

 

Thanks

Guillaume

 

 

 

Edited April 5, 2021 by Willena
Clarify the title

[Willena]

After having spent a lot of time searching for the solution, I finally found it.

 

UART1 is not enabled by default. But referenced in the device-tree. It was as simple as changing some option in the dts.

After figuring out the symbol of UART1 in the symbol section of the dts

 __symbols__ {
   ...
   uart0 = "/serial@ff110000";
   uart1 = "/serial@ff120000";
   uart2 = "/serial@ff130000";
   ...

 

Further in the file we can find more information on the definition of uart1 (also known with symnol serial@ff120000)

serial@ff120000 {
  compatible = "rockchip,rk3328-uart\0snps,dw-apb-uart";
  reg = < 0x00 0xff120000 0x00 0x100 >;
  interrupts = < 0x00 0x38 0x04 >;
  clocks = < 0x02 0x27 0x02 0xd3 >;
  clock-names = "baudclk\0apb_pclk";
  dmas = < 0x12 0x04 0x12 0x05 >;
  dma-names = "tx\0rx";
  pinctrl-names = "default";
  pinctrl-0 = < 0x25 0x26 0x27 >;
  reg-io-width = < 0x04 >;
  reg-shift = < 0x02 >;
  status = "disabled";
  phandle = < 0x85 >;
};

Notice the disabled value in the status field.

Changing the status from 'disabled' to 'okay' did the trick.

After a restart UART1 was available on /dev/ttyS1 \0/