/* Receive a new character from the UART and put it into the receive buffer.  */
void uart_stdio_rx_cb(void *arg, char data)
/* Receive a new character from the UART and put it into the receive buffer.  */
void uart_stdio_rx_cb(void *arg, char data)
{
    (void)arg;
    tsrb_add_one(&_rx_buf, data);
    mutex_unlock(&_rx_mutex);
}