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Introduction

This page is part of the Lifecycle Management with Edge Impulse tutorial series. If you haven’t read the introduction yet, we recommend you to do so here. In this tutorial, we’ll guide you through deploying updated impulses over-the-air (OTA) to Arduino using Edge Impulse. We’ll build on Arduino firmware update workflow, incorporating Edge Impulse’s API to check for updates and download the latest build. Let’s get started!

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Prerequisites:

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Key Features of Arduino OTA Updates:

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Arduino OTA Update

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OTA Code

Here’s the complete C code for implementing OTA updates with Edge Impulse on ESP-EYE (ESP32). 

#include <ESP8266WiFi.h>
#include <ESP8266mDNS.h>
#include <WiFiUdp.h>
#include <ArduinoOTA.h>

const char* ssid = "your-SSID";
const char* password = "your-PASSWORD";

void setup() {
  Serial.begin(115200);
  Serial.println("Booting");
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  while (WiFi.waitForConnectResult() != WL_CONNECTED) {
    Serial.println("Connection Failed! Rebooting...");
    delay(5000);
    ESP.restart();
  }

  // Port defaults to 8266
  ArduinoOTA.setPort(8266);

  // Hostname defaults to esp8266-[ChipID]
  ArduinoOTA.setHostname("myesp8266");

  // No authentication by default
  ArduinoOTA.setPassword((const char *)"123");

  ArduinoOTA.onStart([]() {
    Serial.println("Start");
  });
  ArduinoOTA.onEnd([]() {
    Serial.println("\nEnd");
  });
  ArduinoOTA.onProgress([](unsigned int progress, unsigned int total) {
    Serial.printf("Progress: %u%%\r", (progress / (total / 100)));
  });
  ArduinoOTA.onError([](ota_error_t error) {
    Serial.printf("Error[%u]: ", error);
    if (error == OTA_AUTH_ERROR) Serial.println("Auth Failed");
    else if (error == OTA_BEGIN_ERROR) Serial.println("Begin Failed");
    else if (error == OTA_CONNECT_ERROR) Serial.println("Connect Failed");
    else if (error == OTA_RECEIVE_ERROR) Serial.println("Receive Failed");
    else if (error == OTA_END_ERROR) Serial.println("End Failed");
  });
  ArduinoOTA.begin();
  Serial.println("Ready");
  Serial.print("IP address: ");
  Serial.println(WiFi.localIP());
}

void loop() {
  ArduinoOTA.handle();
}

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Prerequisites

  • A trained impulse in Edge Impulse Studio
  • Installation of required software as detailed in the tutorial

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Preparation

Begin by setting up your device for OTA updates following Espressif’s OTA firmware update workflow. Use the built binary from the C++ example and modify it to incorporate OTA functionality.

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Steps to Deploy Impulse to ESP32

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1. Copy the ESP OTA example and configure your wifi settings

Clone the example repository and adjust it according to your project and connectivity settings. 
mkdir ~/ota-esp32
cd ~/ota-esp32
cp -r $IDF_PATH/examples/system/ota .
idf.py set-target esp32
idf.py menuconfig

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2. Server Side OTA

Modify the ESP OTA example server to check for updates to your project 
import requests
import json
import os

API_KEY = 'your-edge-impulse-api-key'
PROJECT_ID = 'your-project-id'
MODEL_PATH = 'path_to_your_local_model'

def get_last_modification_date():
    url = f'https://studio.edgeimpulse.com/v1/api/{PROJECT_ID}/last-modification-date'
    headers = {'x-api-key': API_KEY}

    response = requests.get(url, headers=headers)
    if response.status_code == 200:
        data = response.json()
        return data['lastModificationDate']
    else:
        print(f"Failed to get last modification date: {response.text}")
        return None

def download_model():
    url = f'https://studio.edgeimpulse.com/v1/api/{PROJECT_ID}/deployment/download'
    headers = {'x-api-key': API_KEY}

    response = requests.get(url, headers=headers)
    if response.status_code == 200:
        with open(MODEL_PATH, 'wb') as file:
            file.write(response.content)
        print("Model downloaded successfully.")
    else:
        print(f"Failed to download the model: {response.text}")

stored_timestamp = None # replace this with logic to get the stored timestamp or hash

# check for recent modifications
last_modification_date = get_last_modification_date()

# compare and download if newer
if last_modification_date and last_modification_date != stored_timestamp:
    print("New model available. Downloading...")
    download_model()

    # update the stored timestamp or hash
    stored_timestamp = last_modification_date

    # restart the device
    os.system('sudo reboot')

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2. Modify the ESP OTA example to check for updates to your project

Modify the Edge Impulse C++ example for ESP32 to check for updates to your project and download the latest build. We will need to add a few libraries to the project to facilitate the OTA update process. These are taken from the ESP32 OTA example and are already included in the example project.

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Components

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1. Non-Volatile Storage (NVS)

#include "nvs.h"
#include "nvs_flash.h"
NVS is utilized to persistently store data like configuration settings, WiFi credentials, or firmware update times, ensuring retention across reboots.

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2. HTTP Client

#include "esp_http_client.h"
This library facilitates HTTP requests to the server for checking and retrieving new firmware updates.

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3. OTA Operations

#include "esp_ota_ops.h"
#include "esp_https_ota.h"
These headers aid in executing OTA operations, including writing new firmware to the flash and switching boot partitions.

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4. FreeRTOS Task

#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
FreeRTOS ensures OTA updates are conducted in a separate task, preventing blockage of other tasks and maintaining system operations during the update.

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3. Updating the Device

Compare the model’s timestamp or hash with the stored version. If it’s different or newer, call the download_model() function.

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4. Monitoring and Repeating the Process

Monitor the device to ensure the new impulse performs as expected and repeat the update process as needed.

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Conclusion

This tutorial provides a comprehensive guide for implementing OTA updates on Espressif ESP-EYE (ESP32) with Edge Impulse. Follow each step meticulously, ensuring all prerequisites and preparation steps are completed before proceeding to the deployment phase. Happy coding! Note: Adjust the code snippets and steps to suit your specific requirements and always ensure to test thoroughly before deploying updates to live environments.