Objective

Understand how to use the FreeRTOS with Espressif. The lab will consist of creating two main tasks. Task 1 must toggle onboard led every 250 ms, and Task 2 must print 'Hello World!' every 2 seconds.

Tasks	Objective
Task 1	Toggle `onboard led` @ 250 ms
Task 2	Print `Hello World!` @ 2 sec

Bonus

Undergrad Bonus:
- Create an additional task that toggles an external led and print it states
Grad Bonus:
- Create an addtional task that runs any led sequence from the previous labs and it should run every 5 seconds

ESP32 Pinout

                                        +-----------------------+
                                        | O      | USB |      O |
                                        |        -------        |
                                    3V3 | [ ]               [ ] | VIN
                                    GND | [ ]               [ ] | GND
    Touch3 / HSPI_CS0 / ADC2_3 / GPIO15 | [ ]               [ ] | GPIO13 / ADC2_4 / HSPI_ID / Touch4
CS / Touch2 / HSPI_WP / ADC2_2 /  GPIO2 | [ ]               [ ] | GPIO12 / ADC2_5 / HSPI_Q / Touch5
     Touch0 / HSPI_HD / ADC2_0 /  GPIO4 | [ ]               [ ] | GPIO14 / ADC2_6 / HSPI_CLK / Touch6
                        U2_RXD / GPIO16 | [ ]               [ ] | GPIO27 / ADC2_7 / Touch7
                        U2_TXD / GPIO17 | [ ]               [ ] | GPIO26 / ADC2_9 / DAC2
                     V_SPI_CS0 /  GPIO5 | [ ]  ___________  [ ] | GPIO25 / ADC2_8 / DAC1
               SCK / V_SPI_CLK / GPIO18 | [ ] |           | [ ] | GPIO33 / ADC1_5 / Touch8 / XTAL32
       U0_CTS / MSIO / V_SPI_Q / GPIO19 | [ ] |           | [ ] | GPIO32 / ADC1_4 / Touch9 / XTAL32
                SDA / V_SPI_HD / GPIO21 | [ ] |           | [ ] | GPIO35 / ADC1_7 
                 CLK2 / U0_RXD /  GPIO3 | [ ] |           | [ ] | GPIO34 / ADC1_6 
                 CLK3 / U0_TXD /  GPIO1 | [ ] |           | [ ] | GPIO39 / ADC1_3 / SensVN 
       SCL / U0_RTS / V_SPI_WP / GPIO22 | [ ] |           | [ ] | GPIO36 / ADC1_0 / SensVP 
               MOSI / V_SPI_WP / GPIO23 | [ ] |___________| [ ] | EN 
                                        |                       |
                                        |  |  |  ____  ____  |  |
                                        |  |  |  |  |  |  |  |  |
                                        |  |__|__|  |__|  |__|  |
                                        | O                   O |
                                        +-----------------------+

Example

Here is a simple example of creating a task with FreeRTOS. The task is called task1 which is it own function. Task 1 will turn the onboard led for 2 seconds and turn off for another 2 seconds.

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
 
#define LOW  0  /* LOGIC LOW*/
#define HIGH 1  /* LOGIC HIGH*/
#define ONBOARD_LED 2 /* ONBOARD LED GPIO Pin*/
 
void task1(void *pvParameters){
    /* Select the GPIO pin that is going to be used */
    esp_rom_gpio_pad_select_gpio(ONBOARD_LED);
    /* Set the direction of the GPIO pin as OUTPUT */
    gpio_set_direction(ONBOARD_LED, GPIO_MODE_OUTPUT);
 
    while(1){
        /*Set the ONBOARD_LED as HIGH | 1 */
        gpio_set_level(ONBOARD_LED, HIGH);
        vTaskDelay(2000 / portTICK_PERIOD_MS); // 2 second delay
        /*Set the ONBOARD_LED as LOW | 0 */
        gpio_set_level(ONBOARD_LED, LOW);
        vTaskDelay(2000 / portTICK_PERIOD_MS); // 2 second delay
    }
}
void app_main(void){
    /* Create task 1 */
    xTaskCreate(&task1, "task1", 2048, NULL, 5, NULL);
}

Lab Template

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
 
/* Define pin 13 as a “BLINK_GPIO” */
#define BLINK_GPIO 13
 
/* Code for the hello_task task */
void hello_task(void *pvParameters)
{
    
}
 
/* Code for the blinky task */
void blinky_task(void *pvParameters)
{
    
}
 
void led_sequence_task(void *pvParameters){
 
}
 
void app_main()
{
    /* Create the task defined by xTaskCreate.*/
    xTaskCreate(&hello_task, "hello_task", 2048, NULL, 5, NULL);
    xTaskCreate(&blinky_task, "blinky_task", 512, NULL, 5, NULL);
 
    /*Create any additional tasks*/
    
}

C helpful functions

For this lab, the most important function call is xTaskCreate which is a function in task.h file. This function has few parameters that must be pass on when calling the function. For instance, if we want to create a simple task that calls example_task which has a stack of 2048, a priority of 5 and it will have no arguments or handle; it will be the following: xTaskCreate( &example_task, example task, 2048, 5, NULL, NULL );

Data type	Variable name	Description
`TaskFunction_t`	pvTaskCode	task function name
`const char *`	pcName	name to associate the task
`configSTACK_DEPTH_TYPE`	usStackDepth	stack size
`UBaseType_t`	uxPriority	task priority
`void *`	pvParameters	arguments
`TaskHandle_t *`	pxCreatedTask	handle to store task

BaseType_t xTaskCreate( 
                         TaskFunction_t pvTaskCode,
                         const char * const pcName,
                         configSTACK_DEPTH_TYPE usStackDepth,
                         void *pvParameters,
                         UBaseType_t uxPriority,
                         TaskHandle_t *pxCreatedTask
                      );

Additional Links

Authors

Jesus Minjares
- Master of Science in Computer Engineering
Erick Baca
- Master of Science in Computer Engineering

GitHub

Lab 3 Repository