As I said before, Espressif has the worst documentation comparing to other chip suppliers. These examples don't have any detailed information, the only thing you can find on their web site is an article about the Iot_Demo, which tells you how to use the program, not explaining how the code works.
I created a very simple blinky program with the Non-OS SDK, it has only one souce file in c, and it does nothing more than blink a LED on the ESP Launcher board. Not using any WiFi or communication APIs, anyway, the SDK forces you to include an initialization code in the user code to tell the chip where is the default parameters for the wireless circuits inside, and it seems the chip goes into Access Point mode though you don't have any code to let it do so.
There is a blue LED connected to MTDI/GPIO12 pin on the ESP Launcher board, what out code does, is to setup a software system timer, then toggle the status of the GPIO12 pin in the callback function. Plus a "Hello World" printed to the serial port. Here is the complete source code:
#include "ets_sys.h"
#include "osapi.h"
#include "gpio.h"
#include "user_interface.h"
uint32 priv_param_start_sec;
/******************************************************************************
* FunctionName : user_rf_cal_sector_set
* Description : SDK just reversed 4 sectors, used for rf init data and paramters.
* We add this function to force users to set rf cal sector, since
* we don't know which sector is free in user's application.
* sector map for last several sectors : ABCCC
* A : rf cal
* B : rf init data
* C : sdk parameters
* Parameters : none
* Returns : rf cal sector
*******************************************************************************/
uint32 ICACHE_FLASH_ATTR
user_rf_cal_sector_set(void)
{
enum flash_size_map size_map = system_get_flash_size_map();
uint32 rf_cal_sec = 0;
switch (size_map) {
case FLASH_SIZE_4M_MAP_256_256:
rf_cal_sec = 128 - 5;
priv_param_start_sec = 0x3C;
break;
case FLASH_SIZE_8M_MAP_512_512:
rf_cal_sec = 256 - 5;
priv_param_start_sec = 0x7C;
break;
case FLASH_SIZE_16M_MAP_512_512:
rf_cal_sec = 512 - 5;
priv_param_start_sec = 0x7C;
break;
case FLASH_SIZE_16M_MAP_1024_1024:
rf_cal_sec = 512 - 5;
priv_param_start_sec = 0xFC;
break;
case FLASH_SIZE_32M_MAP_512_512:
rf_cal_sec = 1024 - 5;
priv_param_start_sec = 0x7C;
break;
case FLASH_SIZE_32M_MAP_1024_1024:
rf_cal_sec = 1024 - 5;
priv_param_start_sec = 0xFC;
break;
case FLASH_SIZE_64M_MAP_1024_1024:
rf_cal_sec = 2048 - 5;
priv_param_start_sec = 0xFC;
break;
case FLASH_SIZE_128M_MAP_1024_1024:
rf_cal_sec = 4096 - 5;
priv_param_start_sec = 0xFC;
break;
default:
rf_cal_sec = 0;
priv_param_start_sec = 0;
break;
}
return rf_cal_sec;
}
/******* toggle LED **************/
void ICACHE_FLASH_ATTR toggle(void)
{
if (GPIO_REG_READ(GPIO_OUT_ADDRESS) & BIT12) // test if GPIO12 is 1
{
gpio_output_set(0, BIT12, 0, 0); // output 0
}
else
{
gpio_output_set(BIT12, 0, 0, 0); // output 1
}
}
/******************************************************************************
* FunctionName : user_init
* Description : entry of user application, init user function here
* Parameters : none
* Returns : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_init(void)
{
LOCAL os_timer_t blink_timer;
os_printf("Hello World from MCU Labs ESP8266\n");
PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTDI_U, FUNC_GPIO12); //set the pin as GPIO
gpio_output_set(0, 0, BIT12, 0); //enable output on GPIO12
os_timer_disarm(&blink_timer);
os_timer_setfn(&blink_timer, (os_timer_func_t*)toggle, NULL); //setup callback
os_timer_arm(&blink_timer, 300, 1); //start timer at an interval of 300ms
}
Here is the video for compiling and running of the code, and the serial port output.
For how to download the code to ESP8266 in Ubuntu, see this article : https://www.mculabs.net/2018/04/downloading-code-to-esp8266-in-ubuntu.html
For how to set Ubuntu to ESP8266's 74880 baudrate, see this: https://www.mculabs.net/2018/04/getting-odd-74880-baudrate-for-esp8266.html
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