hwa/espressif/esp8266/examples/02-1-uart-pin-txd-function/user.c

Toggle the function of GPIO1 between gpio and (uart0,txd).

While booting, the ESP8266 sends messages on uart0 configured at 74880 bps. Toggling DTR (miniterm.py: Ctrl+T,Ctrl+D) allows resetting the device and see these messages.

On the Wemos board, the LED is connected to GPIO2 and is active low (and shared with UART1_TXD):

• the LED is turned off and GPIO1 (TXD) is set low for 100 ms
• the LED is turned on for 400 ms and the uart0 sends the uptime on TXD

user.c

 
/*    make install
 *    python miniterm.py /dev/ttyUSB0 74880
 */
 
#include BOARD_H
 
#define IROM            __attribute__((section (".irom.text")))
#define IRAM
 
#if !defined PIN_LED
#  define PIN_LED       gpio5
#endif
 
 
/*  Function called every 10 ms
 */
void IROM every10ms ( )
{
  static uint8_t        calls ;
 
  calls++ ;
 
  if ( calls == 10 ) {
    /*
     *  Configure GPIO1 as U0TXD to send a message
     */
    hw( write, PIN_LED, 1 );
    hw( configure, gpio1, function, (uart0,txd) );
    os_printf("%d\n", hw_uptime_us());
  }
  else if ( calls >= 50 ) {
    /*
     *  Configure GPIO1 as gpio1 to turn TXD low for 100 ms
     */
    calls = 0 ;
    hw( write, PIN_LED, 0 );
    hw( configure, gpio1, function, gpio, mode, digital_output );
    os_printf("FAIL!\n"); /* That will not be transmitted */
  }
}
 
 
void IROM user_init()
{
  os_printf("Hello World!\n");
 
  hw( configure, PIN_LED, mode, digital_output );
 
  /*  After RESET, GPIO1 is connected to (uart0,txd) so that we can send messages
   *  with os_printf().
   *
   *  Ensure that GPIO1 will be set low when configured as a GPIO.
   */
  hw( write, gpio1, 0 );
  hw( configure, PIN_LED, mode, digital_output );
 
  /*  Trigger a function call every 10 ms (about)
   */
  static os_timer_t timer ;
 
  os_timer_disarm( &timer );
  os_timer_setfn( &timer, (os_timer_func_t *)every10ms, NULL );
  os_timer_arm( &timer, 10, 1 );
}