Get started with ESP-IDF and ESP32-DevKitC: debugging, unit testing, project analysis

The goal of this tutorial is to demonstrate how simple it is to use PlatformIO IDE for VSCode to develop, run and debug a simple Wi-Fi project with the Espressif IoT Development Framework framework for the ESP32-DevKitC board.

Level: Intermediate
Platforms: Windows, Mac OS X, Linux

Requirements:

Downloaded and installed PlatformIO IDE for VSCode
Espressif ESP32 Dev Module
An external debug adapter (e.g. Olimex ARM-USB-OCD)

Setting Up the Project 

Click on “PlatformIO Home” button on the bottom PlatformIO Toolbar:
Click on “New Project”, select Espressif ESP32 Dev Module as the development board, Espressif IoT Development Framework as the framework and a path to the project location (or use the default one):

Adding Code to the Generated Project 

Create a new file main.c in src_dir folder and add the following code:

/*  WiFi softAP Example

   This example code is in the Public Domain (or CC0 licensed, at your option.)

   Unless required by applicable law or agreed to in writing, this
   software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
   CONDITIONS OF ANY KIND, either express or implied.
*/
#include <string.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "esp_mac.h"
#include "esp_wifi.h"
#include "esp_event.h"
#include "esp_log.h"
#include "nvs_flash.h"

#include "lwip/err.h"
#include "lwip/sys.h"

/* The examples use WiFi configuration that you can set via project configuration menu.

   If you'd rather not, just change the below entries to strings with
   the config you want - ie #define EXAMPLE_WIFI_SSID "mywifissid"
*/
#define EXAMPLE_ESP_WIFI_SSID      "mywifissid"
#define EXAMPLE_ESP_WIFI_PASS      "mywifipass"
#define EXAMPLE_ESP_WIFI_CHANNEL   1
#define EXAMPLE_MAX_STA_CONN       4

static const char *TAG = "wifi softAP";

static void wifi_event_handler(void* arg, esp_event_base_t event_base,
                                    int32_t event_id, void* event_data)
{
    if (event_id == WIFI_EVENT_AP_STACONNECTED) {
        wifi_event_ap_staconnected_t* event = (wifi_event_ap_staconnected_t*) event_data;
        ESP_LOGI(TAG, "station "MACSTR" join, AID=%d",
                 MAC2STR(event->mac), event->aid);
    } else if (event_id == WIFI_EVENT_AP_STADISCONNECTED) {
        wifi_event_ap_stadisconnected_t* event = (wifi_event_ap_stadisconnected_t*) event_data;
        ESP_LOGI(TAG, "station "MACSTR" leave, AID=%d",
                 MAC2STR(event->mac), event->aid);
    }
}

void wifi_init_softap(void)
{
    ESP_ERROR_CHECK(esp_netif_init());
    ESP_ERROR_CHECK(esp_event_loop_create_default());
    esp_netif_create_default_wifi_ap();

    wifi_init_config_t cfg = WIFI_INIT_CONFIG_DEFAULT();
    ESP_ERROR_CHECK(esp_wifi_init(&cfg));

    ESP_ERROR_CHECK(esp_event_handler_instance_register(WIFI_EVENT,
                                                        ESP_EVENT_ANY_ID,
                                                        &wifi_event_handler,
                                                        NULL,
                                                        NULL));

    wifi_config_t wifi_config = {
        .ap = {
            .ssid = EXAMPLE_ESP_WIFI_SSID,
            .ssid_len = strlen(EXAMPLE_ESP_WIFI_SSID),
            .channel = EXAMPLE_ESP_WIFI_CHANNEL,
            .password = EXAMPLE_ESP_WIFI_PASS,
            .max_connection = EXAMPLE_MAX_STA_CONN,
            .authmode = WIFI_AUTH_WPA_WPA2_PSK,
            .pmf_cfg = {
                    .required = false,
            },
        },
    };
    if (strlen(EXAMPLE_ESP_WIFI_PASS) == 0) {
        wifi_config.ap.authmode = WIFI_AUTH_OPEN;
    }

    ESP_ERROR_CHECK(esp_wifi_set_mode(WIFI_MODE_AP));
    ESP_ERROR_CHECK(esp_wifi_set_config(WIFI_IF_AP, &wifi_config));
    ESP_ERROR_CHECK(esp_wifi_start());

    ESP_LOGI(TAG, "wifi_init_softap finished. SSID:%s password:%s channel:%d",
             EXAMPLE_ESP_WIFI_SSID, EXAMPLE_ESP_WIFI_PASS, EXAMPLE_ESP_WIFI_CHANNEL);
}

void app_main(void)
{
    //Initialize NVS
    esp_err_t ret = nvs_flash_init();
    if (ret == ESP_ERR_NVS_NO_FREE_PAGES || ret == ESP_ERR_NVS_NEW_VERSION_FOUND) {
      ESP_ERROR_CHECK(nvs_flash_erase());
      ret = nvs_flash_init();
    }
    ESP_ERROR_CHECK(ret);

    ESP_LOGI(TAG, "ESP_WIFI_MODE_AP");
    wifi_init_softap();
}

Warning

Make sure this new file main.c is registered as source file using idf_component_register function in src/CMakeLists.txt file:

idf_component_register(SRCS "main.c")

To compile the project use one of the following options:
- Build option from the Project Tasks menu
- Build button in PlatformIO Toolbar
- Task Menu Tasks: Run Task... > PlatformIO: Build or in PlatformIO Toolbar
- Command Palette View: Command Palette > PlatformIO: Build
- Hotkeys cmd-alt-b / ctrl-alt-b:
If everything went well, we should see a successful result message in the terminal window:
To upload the firmware to the board we can use the following options:
- Upload option from the Project Tasks menu
- Upload button in PlatformIO Toolbar
- Command Palette View: Command Palette > PlatformIO: Upload
- Task Menu Tasks: Run Task... > PlatformIO: Upload
- Hotkeys cmd-alt-u / ctrl-alt-u:

Connect the board to your computer and update the default monitor speed to 115200 in platformio.ini file:

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = espidf
monitor_speed = 115200

Open Serial Monitor to observe the output from the board:
If everything went well, the board should be visible as a WiFi access point:

Debugging the Firmware 

Setting Up the Hardware 

In order to use Debugging, we need to connect an external JTAG probe and the board using the following pins:

ESP32 pin	JTAG probe pin
`3.3V`	`Pin 1(VTref)`
`GPIO 9 (EN)`	`Pin 3 (nTRST)`
`GND`	`Pin 4 (GND)`
`GPIO 12 (TDI)`	`Pin 5 (TDI)`
`GPIO 14 (TMS)`	`Pin 7 (TMS)`
`GPIO 13 (TCK)`	`Pin 9 (TCK)`
`GPIO 15 (TDO)`	`Pin 13 (TDO)`

Specify debug_tool in “platformio.ini” (Project Configuration File). In this tutorial, Olimex ARM-USB-OCD-H debug probe is used:

[env:esp32dev]
platform = espressif32
board = esp32dev
framework = espidf
monitor_speed = 115200
debug_tool = olimex-arm-usb-ocd-h

To start the debug session we can use the following methods:
- Debug: Start debugging in the top menu
- Start Debugging option in the Quick Access menu
- Hotkey button F5:
Walk through the code using control buttons, set breakpoints, and add variables to the Watch window:

Writing Unit Tests 

Note

Functions setUp and tearDown are used to initialize and finalize test conditions. Implementations of these functions are not required for running tests but if you need to initialize some variables before you run a test, you use the setUp function and if you need to clean up variables you use tearDown function.

For the sake of simplicity, let’s create a small library called calculator, implement several basic functions addition, subtraction, multiplication, division and test them using PlatformIO Unit Testing solution.

Create a new folder calculator in the lib_dir folder and add two new files calculator.h and calculator.c with the following contents:

calculator.h:

#ifndef _CALCULATOR_H_
#define _CALCULATOR_H_

#ifdef __cplusplus
extern "C"
{
#endif

  int addition(int a, int b);
  int subtraction(int a, int b);
  int multiplication(int a, int b);
  int division(int a, int b);

#ifdef __cplusplus
}
#endif

#endif // _CALCULATOR_H_

calculator.c:

#include "calculator.h"

int addition(int a, int b)
{
  return a + b;
}

int subtraction(int a, int b)
{
  return a - b;
}

int multiplication(int a, int b)
{
  return a * b;
}

int division(int a, int b)
{
  return a / b;
}

Create a new file test_calc.c to the folder test_dir and add basic tests for the calculator library:

#include <calculator.h>
#include <unity.h>

void setUp(void)
{
  // set stuff up here
}

void tearDown(void)
{
  // clean stuff up here
}

void test_function_calculator_addition(void)
{
  TEST_ASSERT_EQUAL(32, addition(25, 7));
}

void test_function_calculator_subtraction(void)
{
  TEST_ASSERT_EQUAL(20, subtraction(23, 3));
}

void test_function_calculator_multiplication(void)
{
  TEST_ASSERT_EQUAL(50, multiplication(25, 2));
}

void test_function_calculator_division(void)
{
  TEST_ASSERT_EQUAL(32, division(100, 3));
}

void app_main()
{
  UNITY_BEGIN();

  RUN_TEST(test_function_calculator_addition);
  RUN_TEST(test_function_calculator_subtraction);
  RUN_TEST(test_function_calculator_multiplication);
  RUN_TEST(test_function_calculator_division);

  UNITY_END();
}

Let’s run tests on the board and check the results. There should be a problem with test_function_calculator_division test:
Let’s fix the incorrect expected value and run tests again. After processing the results should be correct:

Project Inspection 

For illustrative purposes, let’s imagine we need to find a function with the biggest memory footprint. Also, let’s introduce a bug to our project so Static Code Analysis can report it.

Open PlatformIO Home and navigate to Inspect section, select the current project and press Inspect button:
Project statistics:
The biggest function:
Possible bugs:

Conclusion 

Now we have a project template for the ESP32-DevKitC board that we can use as boilerplate for later projects.

Get started with ESP-IDF and ESP32-DevKitC: debugging, unit testing, project analysis

Setting Up the Project

Adding Code to the Generated Project

Debugging the Firmware

Setting Up the Hardware

Writing Unit Tests

Project Inspection

Conclusion