Initial commit: ZNET Temperature Sensor ESP32 firmware
- PlatformIO project for Meshnology ESP32 LoRa V3 - DS18B20 dual sensor support for tank verification - OLED display for local temperature visibility - HTTP POST to ZNET Web API - WiFiManager for easy WiFi configuration - Offline buffering when network unavailable Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
leehughes
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/**
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* ZNET Temperature Sensor - ESP32 LoRa Gateway
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*
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* Reads DS18B20 temperature sensors in the e-coat paint tank and sends
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* data to ZNET Web for real-time monitoring and ML feature collection.
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*
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* Hardware:
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* - Meshnology ESP32 LoRa V3 (Heltec-compatible)
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* - 2x DS18B20 waterproof temperature probes (1-Wire)
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* - Built-in 0.96" OLED display
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* - Built-in SX1262 LoRa radio (for future sensor nodes)
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*
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* Features:
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* - Dual sensor reading with validation and averaging
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* - OLED display for local temperature visibility
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* - HTTP POST to ZNET Web API
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* - Offline buffering when network is unavailable
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* - LoRa receive for future remote sensor nodes
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* - WiFiManager for easy WiFi setup
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*/
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#include <Arduino.h>
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#include <WiFi.h>
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#include <HTTPClient.h>
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#include <ArduinoJson.h>
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#include <OneWire.h>
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#include <DallasTemperature.h>
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#include <SSD1306Wire.h>
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#include <WiFiManager.h>
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#include "config.h"
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// ============================================================================
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// GLOBALS
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// ============================================================================
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// OneWire and DS18B20
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OneWire oneWire(ONEWIRE_PIN);
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DallasTemperature sensors(&oneWire);
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// Sensor addresses (discovered at startup)
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DeviceAddress sensor1Address;
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DeviceAddress sensor2Address;
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int sensorCount = 0;
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// OLED display
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SSD1306Wire display(OLED_ADDRESS, OLED_SDA, OLED_SCL);
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// Timing
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unsigned long lastTempRead = 0;
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unsigned long lastDisplayUpdate = 0;
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unsigned long lastApiPost = 0;
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// Current readings
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float temperature1_f = 0.0;
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float temperature2_f = 0.0;
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bool sensor1Valid = false;
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bool sensor2Valid = false;
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// Network status
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bool wifiConnected = false;
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int apiFailCount = 0;
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// Offline buffer (circular)
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struct TempReading {
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unsigned long timestamp;
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float temp1_f;
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float temp2_f;
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bool sent;
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};
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TempReading offlineBuffer[OFFLINE_BUFFER_SIZE];
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int bufferHead = 0;
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int bufferCount = 0;
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// ============================================================================
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// FUNCTION DECLARATIONS
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// ============================================================================
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void setupWiFi();
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void setupSensors();
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void setupDisplay();
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void readTemperatures();
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void updateDisplay();
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void postToApi();
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void sendBufferedReadings();
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float celsiusToFahrenheit(float celsius);
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bool isValidTemperature(float temp_f);
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String formatAddress(DeviceAddress addr);
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void displaySplash();
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void displayError(const char* message);
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// ============================================================================
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// SETUP
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// ============================================================================
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void setup() {
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Serial.begin(115200);
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delay(1000);
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Serial.println("\n\n");
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Serial.println("=========================================");
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Serial.println(" ZNET Temperature Sensor v1.0");
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Serial.println(" E-Coat Paint Tank Monitor");
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Serial.println("=========================================");
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// Initialize display first for visual feedback
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setupDisplay();
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displaySplash();
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// Initialize sensors
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setupSensors();
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// Connect to WiFi
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setupWiFi();
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Serial.println("\nSetup complete. Starting main loop...\n");
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}
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// ============================================================================
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// MAIN LOOP
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// ============================================================================
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void loop() {
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unsigned long now = millis();
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// Check WiFi connection
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wifiConnected = WiFi.status() == WL_CONNECTED;
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// Read temperatures at interval
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if (now - lastTempRead >= TEMP_READ_INTERVAL_MS || lastTempRead == 0) {
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readTemperatures();
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lastTempRead = now;
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// Try to post to API
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if (wifiConnected) {
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postToApi();
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// Also try to send any buffered readings
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if (bufferCount > 0) {
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sendBufferedReadings();
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}
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} else {
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// Buffer the reading for later
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if (bufferCount < OFFLINE_BUFFER_SIZE) {
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offlineBuffer[bufferHead].timestamp = now;
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offlineBuffer[bufferHead].temp1_f = temperature1_f;
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offlineBuffer[bufferHead].temp2_f = temperature2_f;
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offlineBuffer[bufferHead].sent = false;
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bufferHead = (bufferHead + 1) % OFFLINE_BUFFER_SIZE;
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bufferCount++;
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Serial.printf("Buffered reading (count: %d)\n", bufferCount);
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}
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}
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}
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// Update display more frequently
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if (now - lastDisplayUpdate >= DISPLAY_UPDATE_INTERVAL_MS) {
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updateDisplay();
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lastDisplayUpdate = now;
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}
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// Small delay to prevent watchdog issues
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delay(10);
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}
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// ============================================================================
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// WIFI SETUP
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// ============================================================================
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void setupWiFi() {
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display.clear();
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display.setTextAlignment(TEXT_ALIGN_CENTER);
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display.drawString(64, 20, "Connecting to WiFi...");
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display.display();
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// Check if we have hardcoded credentials
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if (strlen(WIFI_SSID) > 0) {
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Serial.printf("Connecting to WiFi: %s\n", WIFI_SSID);
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WiFi.begin(WIFI_SSID, WIFI_PASSWORD);
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int attempts = 0;
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while (WiFi.status() != WL_CONNECTED && attempts < 20) {
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delay(500);
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Serial.print(".");
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attempts++;
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}
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if (WiFi.status() == WL_CONNECTED) {
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Serial.println("\nWiFi connected!");
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Serial.printf("IP: %s\n", WiFi.localIP().toString().c_str());
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wifiConnected = true;
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return;
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}
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}
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// Use WiFiManager for captive portal setup
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Serial.println("Starting WiFiManager...");
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display.clear();
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display.drawString(64, 10, "WiFi Setup");
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display.drawString(64, 30, "Connect to:");
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display.drawString(64, 45, "ZNET-TempSensor");
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display.display();
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WiFiManager wm;
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wm.setConfigPortalTimeout(180); // 3 minute timeout
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if (!wm.autoConnect("ZNET-TempSensor", "znettemp123")) {
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Serial.println("Failed to connect - restarting...");
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delay(3000);
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ESP.restart();
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}
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Serial.println("WiFi connected via WiFiManager!");
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Serial.printf("IP: %s\n", WiFi.localIP().toString().c_str());
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wifiConnected = true;
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}
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// ============================================================================
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// SENSOR SETUP
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// ============================================================================
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void setupSensors() {
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Serial.println("Initializing DS18B20 sensors...");
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sensors.begin();
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sensorCount = sensors.getDeviceCount();
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Serial.printf("Found %d sensor(s)\n", sensorCount);
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if (sensorCount == 0) {
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Serial.println("ERROR: No sensors found!");
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displayError("No sensors found!");
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return;
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}
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// Get addresses
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if (sensorCount >= 1) {
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if (sensors.getAddress(sensor1Address, 0)) {
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Serial.printf("Sensor 1: %s\n", formatAddress(sensor1Address).c_str());
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}
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}
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if (sensorCount >= 2) {
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if (sensors.getAddress(sensor2Address, 1)) {
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Serial.printf("Sensor 2: %s\n", formatAddress(sensor2Address).c_str());
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}
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}
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// Set resolution (12-bit = 0.0625°C precision)
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sensors.setResolution(12);
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// Don't wait for conversion (we'll handle timing ourselves)
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sensors.setWaitForConversion(false);
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}
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// ============================================================================
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// TEMPERATURE READING
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// ============================================================================
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void readTemperatures() {
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Serial.println("Reading temperatures...");
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// Request temperatures from all sensors
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sensors.requestTemperatures();
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// Wait for conversion (750ms for 12-bit)
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delay(750);
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// Read sensor 1
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if (sensorCount >= 1) {
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float tempC = sensors.getTempC(sensor1Address);
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if (tempC != DEVICE_DISCONNECTED_C) {
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temperature1_f = celsiusToFahrenheit(tempC);
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sensor1Valid = isValidTemperature(temperature1_f);
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Serial.printf("Sensor 1: %.2f°F %s\n", temperature1_f,
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sensor1Valid ? "(valid)" : "(INVALID)");
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} else {
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sensor1Valid = false;
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Serial.println("Sensor 1: DISCONNECTED");
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}
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}
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// Read sensor 2
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if (sensorCount >= 2) {
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float tempC = sensors.getTempC(sensor2Address);
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if (tempC != DEVICE_DISCONNECTED_C) {
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temperature2_f = celsiusToFahrenheit(tempC);
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sensor2Valid = isValidTemperature(temperature2_f);
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Serial.printf("Sensor 2: %.2f°F %s\n", temperature2_f,
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sensor2Valid ? "(valid)" : "(INVALID)");
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} else {
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sensor2Valid = false;
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Serial.println("Sensor 2: DISCONNECTED");
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}
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}
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// Check for sensor agreement (if both valid)
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if (sensor1Valid && sensor2Valid) {
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float diff = abs(temperature1_f - temperature2_f);
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if (diff > 5.0) {
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Serial.printf("WARNING: Sensors disagree by %.1f°F\n", diff);
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}
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}
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}
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// ============================================================================
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// DISPLAY UPDATE
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// ============================================================================
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void updateDisplay() {
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display.clear();
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// Title bar
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display.setTextAlignment(TEXT_ALIGN_LEFT);
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display.setFont(ArialMT_Plain_10);
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display.drawString(0, 0, "ZNET Tank Temp");
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// WiFi status indicator
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display.setTextAlignment(TEXT_ALIGN_RIGHT);
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display.drawString(128, 0, wifiConnected ? "WiFi OK" : "NO WiFi");
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// Horizontal line
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display.drawLine(0, 12, 128, 12);
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// Temperature readings
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display.setTextAlignment(TEXT_ALIGN_CENTER);
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display.setFont(ArialMT_Plain_16);
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if (sensor1Valid) {
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char buf[20];
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snprintf(buf, sizeof(buf), "%.1f°F", temperature1_f);
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display.drawString(64, 18, buf);
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} else {
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display.drawString(64, 18, "---");
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}
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display.setFont(ArialMT_Plain_10);
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display.drawString(64, 36, "Primary");
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// Secondary sensor (smaller, below)
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if (sensorCount >= 2) {
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display.setFont(ArialMT_Plain_10);
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if (sensor2Valid) {
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char buf[20];
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snprintf(buf, sizeof(buf), "Backup: %.1f°F", temperature2_f);
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display.drawString(64, 50, buf);
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} else {
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display.drawString(64, 50, "Backup: ---");
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}
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}
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// Buffer indicator (if offline)
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if (bufferCount > 0) {
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display.setTextAlignment(TEXT_ALIGN_LEFT);
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char buf[20];
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snprintf(buf, sizeof(buf), "Buf:%d", bufferCount);
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display.drawString(0, 54, buf);
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}
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display.display();
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}
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// ============================================================================
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// API POSTING
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// ============================================================================
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void postToApi() {
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if (!wifiConnected) {
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Serial.println("No WiFi - skipping API post");
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return;
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}
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Serial.println("Posting to ZNET Web API...");
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HTTPClient http;
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http.begin(ZNET_API_URL);
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http.addHeader("Content-Type", "application/json");
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http.setTimeout(HTTP_TIMEOUT_MS);
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// Build JSON payload
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JsonDocument doc;
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doc["device_id"] = DEVICE_ID;
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doc["device_name"] = DEVICE_NAME;
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doc["timestamp"] = millis(); // Server will use its own timestamp
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JsonArray readings = doc["readings"].to<JsonArray>();
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// Sensor 1
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if (sensor1Valid) {
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JsonObject r1 = readings.add<JsonObject>();
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r1["sensor_id"] = SENSOR_1_NAME;
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r1["temperature_f"] = round(temperature1_f * 100) / 100.0; // 2 decimal places
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r1["is_valid"] = true;
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}
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// Sensor 2
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if (sensor2Valid) {
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JsonObject r2 = readings.add<JsonObject>();
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r2["sensor_id"] = SENSOR_2_NAME;
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r2["temperature_f"] = round(temperature2_f * 100) / 100.0;
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r2["is_valid"] = true;
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}
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String jsonString;
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serializeJson(doc, jsonString);
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Serial.printf("Payload: %s\n", jsonString.c_str());
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int httpCode = http.POST(jsonString);
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if (httpCode == HTTP_CODE_OK || httpCode == HTTP_CODE_CREATED) {
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Serial.printf("API POST success (code %d)\n", httpCode);
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apiFailCount = 0;
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// Parse response for any config updates
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String response = http.getString();
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Serial.printf("Response: %s\n", response.c_str());
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} else {
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Serial.printf("API POST failed (code %d)\n", httpCode);
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apiFailCount++;
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if (httpCode > 0) {
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String response = http.getString();
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Serial.printf("Error response: %s\n", response.c_str());
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}
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}
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http.end();
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}
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void sendBufferedReadings() {
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// TODO: Implement batch sending of buffered readings
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// For now, just clear the buffer on successful connection
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Serial.printf("Would send %d buffered readings\n", bufferCount);
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// Clear buffer (proper implementation would send each reading)
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bufferCount = 0;
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bufferHead = 0;
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}
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// ============================================================================
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// UTILITY FUNCTIONS
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// ============================================================================
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float celsiusToFahrenheit(float celsius) {
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return celsius * 9.0 / 5.0 + 32.0;
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}
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bool isValidTemperature(float temp_f) {
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return temp_f >= TEMP_MIN_VALID_F && temp_f <= TEMP_MAX_VALID_F;
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}
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String formatAddress(DeviceAddress addr) {
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char buf[20];
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snprintf(buf, sizeof(buf), "%02X%02X%02X%02X%02X%02X%02X%02X",
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addr[0], addr[1], addr[2], addr[3],
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addr[4], addr[5], addr[6], addr[7]);
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return String(buf);
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}
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void setupDisplay() {
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display.init();
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display.flipScreenVertically();
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display.setFont(ArialMT_Plain_10);
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display.setTextAlignment(TEXT_ALIGN_CENTER);
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}
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void displaySplash() {
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display.clear();
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display.setFont(ArialMT_Plain_16);
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display.drawString(64, 10, "ZNET");
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display.setFont(ArialMT_Plain_10);
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display.drawString(64, 30, "Tank Temperature");
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display.drawString(64, 45, "v1.0");
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display.display();
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delay(2000);
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}
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void displayError(const char* message) {
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display.clear();
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display.setFont(ArialMT_Plain_10);
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display.setTextAlignment(TEXT_ALIGN_CENTER);
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display.drawString(64, 20, "ERROR");
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display.drawString(64, 35, message);
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display.display();
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}
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