Objective

Understand how to use the gpio driver library from Espressif. The lab will consist of creating a sweeper and a led chaser. The sweeper will iterate over mutiple LEDs by turning from the lowest to highest bit and then highest to lowest bit. While led chaser will have a single led iterating from the lowest to highest bit. For both the sweeper and led chaser use up to 6 GPIOs.

Bonus

Undergrad Bonus:
- Do the led chaser
Grad Bonus:
- Create a light show with different sequences and patterns as you like. Have fun!

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 an example of a how to use ESP32 GPIO function calls. The program toggles the onboard LED every other second.

#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 app_main(void){
  esp_rom_gpio_pad_select_gpio(ONBOARD_LED); /* select the GPIO pins */
  gpio_set_direction(ONBOARD_LED, GPIO_MODE_OUTPUT); /* set as output */
 
  while(1){
    gpio_set_level(ONBOARD_LED, HIGH); /* set high */
    vTaskDelay(1000 / portTICK_PERIOD_MS); /* 1 second delay */
    gpio_set_level(ONBOARD_LED, LOW); /* set low */
    vTaskDelay(1000 / portTICK_PERIOD_MS); /* 1 second delay */
  }  
}

Lab Template

#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*/
 
void setOutputs(uint8_t *out, int size)
{
    /* iterate over the size of the array */
    for (int i = 0; i < size; i++) 
    {
        esp_rom_gpio_pad_select_gpio(out[i]); /* select the GPIO pins */
        gpio_set_direction(out[i], GPIO_MODE_OUTPUT); /* set direction as outputs */
    }
    return;
}
 
void sweep(uint8_t *led, int size)
{
    /* iterate over the size of the array */
    for ( int i = 0; i < size; i++)
    {
        
    }
    /* iterate over the size of the array */
    for (int i = size - 1; i >= 0; i--)
    {
      
    }
}
 
void led_chaser(uint8_t *led, int size)
{
    /* iterate over the size of the array */
    for (int i = 0; i < size; i++)
    {
      
    }
    /* iterate over the size of the array */
    for (int i = size - 1; i >= 0; i--)
    {
      
    }
}
 
void lightShow(uint8_t *led, int size)
{
    /*Use all prior functions to create a custom light show */
}
 
void app_main(void)
{
    /*GPIOs pins*/
    uint8_t led[] = {2}; /* create an array of single led */
    int size = sizeof(led)/sizeof(uint8_t); /* get size of the array, use sizeof() to allow scalabilty */
    setOutputs(led,size); /* intialize GPIOs pins */
    while (1)
    {
      /* Added led patterns */
 
      /* Toggle LED using index of your array */
      gpio_set_level(led[0], LOW);
      vTaskDelay(1000 / portTICK_PERIOD_MS); /* 1 second delay */
      gpio_set_level(led[0], HIGH);
      vTaskDelay(1000 / portTICK_PERIOD_MS); /* 1 second delay */
    }
}

C helpful functions

For this lab, there are three main functions from Espressif that are important. First, is to select which GPIO pin is going to be used by the following function: esp_rom_gpio_pad_select_gpio(gpio_num_t gpio_num). The first parameter gpio_num is the GPIO pin that is going to be used, for instance if we want to use the onboard led we should put a 2 on gpio_num such as esp_rom_gpio_pad_select_gpio(2).

esp_err_t esp_rom_gpio_pad_select_gpio(gpio_num_t gpio_num);

Next, gpio_set_direction(gpio_num_t gpio_num, gpio_mode_t mode) allows the user to set the direction of the GPIO pin. For this lab we are only going to use *GPIO_MODE_OUTPUT* for the mode.

esp_err_t gpio_set_direction(gpio_num_t gpio_num, gpio_mode_t mode);

Furthermore, gpio_set_level(gpio_num_t gpio_num, uint32_t level) sets the logic level of the GPIO pin that we pass through the function.

Value	Logic
0	low
1	high

esp_err_t gpio_set_level(gpio_num_t gpio_num, uint32_t level);

Lastly, the following function vTaskDelay(const TickType_t xTicksToDelay) is use to generate delay with ESP32 and its part of FreeRTOS, you will learn more of it in later labs. Therefore, for this lab just use it to generate delay in milliseconds.

void vTaskDelay(const TickType_t xTicksToDelay);

Warning!

Depending of the version of ESP-IDF that you may have, some libraries and function calls that may be deprecate! If you get an warning message when using esp_rom_gpio_pad_select_gpio please use gpio_pad_select_gpio.

Additional Links

Espressif GPIO Driver API

Authors

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

GitHub

Lab 0 Repository