Microprocessor 2 Labs v2.0
Microprocessor 2 Lab Documenation
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Lab 6 GPIO, Interrupts, and Queues

Objective

  • Understand how to use queues and interrupts with FreeRTOS Queues. In this lab, students will learn how to send data between tasks using interrupts. Student must create a program that uses gpio interrupts as in Lab 2, please feel free to use either configuration (Pull-up | Pull-down). The interrupt service routine (ISR) should send data (gpio pin number) to a queue and be receive by task: print_task. The print_task must receive the data and display it. For instance, if the interrupt was trigger by pin 23, the output would be: "GPIO 23 received!!!".
Task Objective
print_task Receive data and print to terminal/monitor

Interrupt Objective
gpio_isr Send data to print_task

Bonus

  • Undergrad Bonus
    • Modify code to use 2 more interrupts.
  • Grad Bonus
    • Modify code to use 2 more interrupts and add 2 LEDs. Each interrupt must toggle its corresponding LED.

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 advance setup. The following code will have an external LED toggling every half second and will toggle the onboard led if the button is pressed.

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#define ESP_INTR_FLAG_DEFAULT 0 /* Interrupt flag configuration */
#define LOW 0 /* low logic */
#define HIGH 1 /* high logic */
#define ONBOARD_LED 2 /* onboard led pin */
#define EXTERNAL_LED 22 /* external led pin */
#define BUTTON 23 /* button pin */
void toggle(gpio_num_t pin){
/* Get current level and toggle LED */
static bool on;
gpio_set_level(pin, on);
on = !on;
}
/* GPIO interrupt handler */
static void IRAM_ATTR gpio_isr_handler(void* arg) {
/* store argument */
gpio_num_t gpio = (gpio_num_t) arg;
/* toggle LED */
toggle(gpio);
}
/* GPIO setup */
void gpio_setup(void){
/* IO configuration */
gpio_config_t io_conf;
/* Input configuration */
io_conf.intr_type = GPIO_INTR_POSEDGE; /* Set up as Positive Edge */
io_conf.mode = GPIO_MODE_INPUT; /* Set pins as input */
io_conf.pin_bit_mask = (1ULL << BUTTON); /* Add input bit mask */
io_conf.pull_down_en = 1; /* Enable pulldown */
io_conf.pull_up_en = 0; /* Disable pullup */
/* Set configuration */
gpio_config(&io_conf);
/* Output configuration */
io_conf.intr_type = GPIO_INTR_DISABLE; /* Disable interrupt */
io_conf.mode = GPIO_MODE_OUTPUT; /* Set as output*/
io_conf.pin_bit_mask = (1ULL << ONBOARD_LED) | (1ULL << EXTERNAL_LED); /* Add output bit mask */
io_conf.pull_down_en = 0; /* Disable pulldown */
io_conf.pull_up_en = 0; /* Disable pullup */
/* Set configuration */
gpio_config(&io_conf);
/* Set default interrupt flag */
gpio_install_isr_service(ESP_INTR_FLAG_DEFAULT);
/* Add ISR handler */
gpio_isr_handler_add(BUTTON, gpio_isr_handler, (void*) ONBOARD_LED);
}
void app_main() {
/* Setup the GPIOs */
gpio_setup();
while(1){
toggle(EXTERNAL_LED); /* Toggle external led */
vTaskDelay(500/portTICK_PERIOD_MS); /* .5 second delay */
}
}
app_main
void app_main()
Definition main.c:261
ONBOARD_LED
#define ONBOARD_LED
Definition main.c:31
ESP_INTR_FLAG_DEFAULT
#define ESP_INTR_FLAG_DEFAULT
Definition main.c:29

Lab Template

#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "freertos/queue.h"
#include "driver/gpio.h"
#define ESP_INTR_FLAG_DEFAULT 0 /* Interrupt flag configuration */
/* Global Queue handle */
QueueHandle_t xQueue;
/* GPIO interrupt handler */
static void IRAM_ATTR gpio_isr_handler(void *arg)
{
}
/* Print task */
void print_task(void *pvParameters)
{
}
/* GPIO interrupt setup */
void gpio_interrupt_setup(void)
{
}
void app_main()
{
/* Create a queue */
/* Call gpio interrupt setup */
gpio_interrupt_setup();
/* Create task */
xTaskCreate(&print_task, "print_task", 2048, NULL, 10, NULL);
}
xQueue
QueueHandle_t xQueue
Definition main.c:72
gpio_interrupt_setup
void gpio_interrupt_setup(void)
Definition main.c:59
print_task
void print_task(void *pvParameters)
Definition main.c:53

C helpful functions

We have use queues in the previous lab to send data from one task to another. However, in this lab we need to send data from an interrupt to a task. Therefore, a special function is needed to send data to the queue: xQueueSendFromISR(). Similar to the previous lab functions that we have use to send data in a queue, xQueueSendFromISR is similar with a different parameter. To keep it simple, please set BaseType_t *pxHigherPriorityTaskWoken parameter set to NULL.

BaseType_t xQueueSendFromISR(
QueueHandle_t xQueue,
const void *pvItemToQueue,
BaseType_t *pxHigher PriorityTaskWoken
);

For more information of how to use Queues and Interrupts, please see previous labs.

Pull-up and Pull-down Configuration

button configuation

Additional Links

Authors

GitHub

Lab 6 Repository

Read Next: Lab 7