Post History

Communication with microcontroller via usart - using strings a good idea?

I have a PCB with an onboard microcontroller that I use to turn on and off a bunch of switches/relays. To control which relay should be on I use my computer to communicate via USART to the microcontroller, with a local python script sending commands.

Right now, I have it set up such that my python script sends two things. First, a string containing the command. Second, the switch number that the command affects.

```python
#main.py
establish_usart_connection()
usart.write(b'RELAY_ON\n')
usart.write(bytes([1])) #Turn on channel 1
end_usart_connection()
```

Then in my microcontroller code I always wait to receive both a string-command and a number. Then, I compare the string-command with my cases using `strcmp` to determine what the microcontroller should do. Essentially something like this.

```C
#include <string.h>

#define USART_BUFFER_SZ 64
static uint8_t usart_buffer[USART_BUFFER_SZ] = {0};
static uint8_t switch_number = 0;
int main(void)
{
    usart_receive_line(usart_buffer, USART_BUFFER_SZ);
    switch_number = usart_rx(); //Infinite while loop until receiving a number
    if(strcmp((const char*)usart_buffer, "RELAY_ON") == 0)
    {
        digital_write(relay_arr[switch_number],HIGH);
    }
    else if(strcmp((const char*)usart_buffer, "RELAY_OFF") == 0)
    {
        /* Turn off relay instead */
    }
}
```

**Question**: Is it a good approach to use strings when communicating via usart? In my opinion it makes the code easier to read, because you can clearly see that "okay this commands turns on a relay". The issue that I imagine though, is that this is not a robust approach. But maybe I'm wrong?

Also, with this approach I have to include the `string.h` library in my microcontroller code in order to use `strcmp()` which just seems a little silly/unnecessary because of the overhead.