Cannot initialize multiple stdio UART driver instances

[alastairpatrick]

The API does not prevent an attempt to initialize multiple UART stdio driver instances. I can't find any documentation saying this isn't allowed. It would also be possible to implement. For example:

int main() {
  stdio_uart_init_full(uart0, 115200, 0, 1);
  stdio_uart_init_full(uart1, 115200, 6, 7);

  printf("Hello world!\r\n");

  for (;;);
}

The expectation here might be that the greeting is output to both UARTs.

This could be fixed by changing the documentation and maybe adding a runtime assertion or by actually making it work.

If it's going to work, issue #811 is impacted because the signature of stdio_uart_deinit_full() should change to identify which UART driver instance is uninitialized:

void stdio_uart_deinit_full(uart_inst_t* instance, int tx_pin, int rx_pin);

Somewhat more involved, it would be useful if something like this worked:

  stdio_uart_init_full(uart0, 115200, 0, 1);
  stdio_uart_init_full(uart1, 115200, 6, 7);

  fprintf(uart0_handle, "Hello from uart0!\r\n");

  fprintf(uart1_handle, "Hello from uart1!\r\n");

[kilograham]

Having uart0_handle and uart1_handle is quite a nice idea

[ekholm]

May I suggest to use the more standard handles, stdout and stderr, stdin.
And in startup code application can initialize which uart(or usb) is what pipe

[kilograham]

Somewhat more involved, it would be useful if something like this worked:

stdio_uart_init_full(uart1, 115200, 6, 7);

fprintf(uart0_handle, "Hello from uart0!\r\n");

fprintf(uart1_handle, "Hello from uart1!\r\n");

See #1715 which would add support for more handles

[kilograham]

May I suggest to use the more standard handles, stdout and stderr, stdin. And in startup code application can initialize which uart(or usb) is what pipe

I think @alastairpatrick 's point was that the uartn_ handles could be used in addition to stdout etc. for finer grained control