Lab 1 LED Controller

Objective

• Understand how to use the gpio driver library from Espressif. The lab will consist of using a sweeper, led chaser and any additional led sequence that the student developed and be selected via an input. Students must have a total of three buttons. First button must start sweeper function which student must have completed from the previous lab. Next, the second button must start the led chaser function. Lastly, the third button must toggle the state of the onboard led.

Button	Function	Mode
B0	Sweeper	Pull-down
B1	Led chaser	Pull-down
B2	Toggle	Pull-down

Bonus

• Undergrad Bonus:
  • Create another LED sequence and add another button, as pull-up.
• Grad Bonus:
  • Add button to start lightshow from previous lab, as pull-up
  • Do a reset button which will turns off all LEDs, as pull-up

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 how to use ESP32 GPIO function calls for inputs. The following code will turn the onboard LED as long as the button is pressed.

#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*/
 
#define BUTTON_0 23 /* Button 0 */
 
void app_main(void){
 
  /* Initialize OUTPUTs */
  esp_rom_gpio_pad_select_gpio(ONBOARD_LED); /* select GPIO pins */
  gpio_set_direction(ONBOARD_LED, GPIO_MODE_OUTPUT); /* set as output */
 
  /* Intialize INPUTs */
  esp_rom_gpio_pad_select_gpio(BUTTON_0); /* select GPIO pin */
  gpio_set_direction(BUTTON_0, GPIO_MODE_INPUT); /* set as input */
  gpio_set_pull_mode(BUTTON_0, GPIO_PULLDOWN_ONLY); /* set as pull-down */
 
  while(1){
    /* read gpio level */
    int res = gpio_get_level(BUTTON_0); 
    vTaskDelay(10/portTICK_PERIOD_MS); /* debounce button */
    
    /* Check return value */
    if(res == 1){
        gpio_set_level(ONBOARD_LED, HIGH); /* set high */
    }else{
        gpio_set_level(ONBOARD_LED, LOW); /* set low */
    }
    
    /* ternary operator */
    //res ? gpio_set_level(ONBOARD_LED, HIGH) : gpio_set_level(ONBOARD_LED, LOW);
    
    vTaskDelay(100/portTICK_PERIOD_MS); /* avoid WDT trigger */
  }  
}

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 setInputs(uint8_t *in, int size)
{
    /* iterate over the size of the array */
    for (int i = 0; i < size; i++)
    {
        /* select the GPIO pins */
 
        /* set direction as inputs */
 
        /* set as pull-down */
 
    }
    return;
}
void setOutputs(uint8_t *out, int size)
{
    /* iterate over the size of the array */
    for (int i = 0; i < size; i++) 
    {
       
    }
    return;
}
 
void sweep(uint8_t *led, int size)
{
   
}
 
/*Replace with yours*/
void light_show(){
 
}
 
void led_chaser(uint8_t *led, int size)
{
 
}
 
void app_main(void)
{
    /* Select GPIOs output and store in led array */
    uint8_t led[] = {13}; /*replace with your GPIO pins */
    
    /* Select GPIOs inputs and store in button array */
    uint8_t button[] = {22, 23};
 
    /* Use sizeof() to get the size of the arrays */
    int led_size = sizeof(led) / sizeof(uint8_t);
    int button_size = sizeof(button) / sizeof(uint8_t);
 
    /* Initialize Inputs */
    setInputs(button, button_size);
 
    /* Initialize Outputs */
    setOutputs(led, led_size);
 
    while (1)
    {
        vTaskDelay(5/portTICK_PERIOD_MS); /* debounce button */
        int button0 = gpio_get_level(button[0]); /* read button 0 */
        /* add additonal buttons */ 
        if(button0 == 1){
         
        }
        else{
          vTaskDelay(100/portTICK_PERIOD_MS); /* 100ms to avoid WDT errors */
        }
    }
}

C helpful functions

For this lab, there are additional functions from Espressif that are important for using inputs. As the previous lab, we must set the direction of the GPIO pin by using gpio_set_direction(gpio_num_t gpio_num, gpio_mode_t mode). Previously we used GPIO_MODE_OUTPUT as we using outputs, however, now that we will be using inputs, we need GPIO_MODE_INPUT.

esp_err_t gpio_set_direction(gpio_num_t gpio_num, gpio_mode_t mode);

Next, as the name states gpio_get_level(gpio_num_tgpio_num) returns the current level of the GPIO pin whether it high and low. This function is use to get the current state of the input.

int gpio_get_level(gpio_num_ tgpio_num);

Value	Logic
0	low
1	high

Lastly, there are two additional functions that are crucial when using inputs. There are two configurations for inputs either pull-up or pull-down: gpio_pulldown_en(gpio_num_t gpio_num) and gpio_pullup_en(gpio_num_t gpio_num). Down below are the configuration for both pull-up and pull-down.

esp_err_t gpio_pullup_en(gpio_num_t gpio_num);

esp_err_t gpio_pulldown_en(gpio_num_t gpio_num);

Pull-up and Pull-down Configuration

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 1 Repository

Read Next: Lab 2