espterm-firmware/user/stdout.c

//Stupid bit of code that does the bare minimum to make os_printf work.

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * Jeroen Domburg <jeroen@spritesmods.com> wrote this file. As long as you retain 
 * this notice you can do whatever you want with this stuff. If we meet some day, 
 * and you think this stuff is worth it, you can buy me a beer in return. 
 * ----------------------------------------------------------------------------
 */

#include <esp8266.h>
#include <uart_hw.h>

static void ICACHE_FLASH_ATTR stdoutUartTxd(char c) {
	//Wait until there is room in the FIFO
	while (((READ_PERI_REG(UART_STATUS(0))>>UART_TXFIFO_CNT_S)&UART_TXFIFO_CNT)>=126) ;
	//Send the character
	WRITE_PERI_REG(UART_FIFO(0), c);
}

static void ICACHE_FLASH_ATTR stdoutPutchar(char c) {
	//convert \n -> \r\n
	if (c=='\n') stdoutUartTxd('\r');
	stdoutUartTxd(c);
}


void stdoutInit() {
	//Enable TxD pin
	PIN_PULLUP_DIS(PERIPHS_IO_MUX_U0TXD_U);
	PIN_FUNC_SELECT(PERIPHS_IO_MUX_U0TXD_U, FUNC_U0TXD);
	
	//Set baud rate and other serial parameters to 115200,n,8,1
	uart_div_modify(0, UART_CLK_FREQ/BIT_RATE_115200);
	WRITE_PERI_REG(UART_CONF0(0), (STICK_PARITY_DIS)|(ONE_STOP_BIT << UART_STOP_BIT_NUM_S)| \
				(EIGHT_BITS << UART_BIT_NUM_S));

	//Reset tx & rx fifo
	SET_PERI_REG_MASK(UART_CONF0(0), UART_RXFIFO_RST|UART_TXFIFO_RST);
	CLEAR_PERI_REG_MASK(UART_CONF0(0), UART_RXFIFO_RST|UART_TXFIFO_RST);
	//Clear pending interrupts
	WRITE_PERI_REG(UART_INT_CLR(0), 0xffff);

	//Install our own putchar handler
	os_install_putc1((void *)stdoutPutchar);
}