Initial version

.gitignore

@@ -0,0 +1 @@
+.pio

platformio.ini

@@ -0,0 +1,20 @@
+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:heltec_wifi_lora_32_V2]
+platform = espressif32
+board = heltec_wifi_lora_32_V2
+framework = arduino
+
+lib_deps =
+  Heltec ESP32 Dev-Boards@1.0.9
+  TTN_esp32@0.1.0
+
+lib_ldf_mode = deep

src/main.cpp

@@ -0,0 +1,102 @@
+#include <TTN_esp32.h>
+#include "heltec.h"
+#include "config.h"
+#include "main.h"
+
+TTN_esp32 ttn;
+
+void loop() {
+  // Read voltage and add as uint8 to transmission
+  float voltage = readVoltage();
+  uint8_t payload = (uint8_t)(int)(voltage * 10);
+
+  if (ENABLE_SEND) {
+    sendVoltage(payload);
+  } else {
+    // Sending is disabled, display value and give a moment to read
+    Heltec.display->drawString(0, 22, "Current Voltage: " + String((float)payload / 10) + "V");
+    Heltec.display->display();
+    delay(1000);
+  }
+
+  if (voltage >= BATTERY_LOAD_VOLTAGE || DISABLE_SLEEP) {
+    // We're getting power from the charger, no need to deep sleep.
+    // Just wait for a moment to do the next measurement which will
+    // allow us to receive a measurement shortly after car shuts down.
+    delay(CHARGE_SLEEP_MS);
+  } else {
+    // We're running on battery and should preserve as much power
+    // as possible, so we power down and ask in a few minutes again.
+    esp_sleep_enable_timer_wakeup(BATTERY_SLEEP_US);
+    esp_deep_sleep_start();
+  }
+}
+
+float readVoltage() {
+  Serial.println("Reading voltage...");
+
+  int rawSum = 0;
+  for (int i = 0; i < MEAS_COUNT; i++) {
+    rawSum += analogRead(PIN_VOLTAGE_READ);
+    delay(MEAS_WAIT_MS);
+  }
+
+  float raw = rawSum / float(MEAS_COUNT);
+  float vout = raw * 3.3 / 4094.0;
+  float value = vout / (7500.0 / (30000.0 + 7500.0)) + CORRECT_DIFF;
+
+  Serial.printf("Voltage read: %.1f %.2f\r\n", raw, value);
+  return value;
+}
+
+void sendVoltage(uint8_t payload) {
+  // Make sure any pending transactions are handled first
+  ttn.waitForPendingTransactions();
+
+  Heltec.display->clear();
+  // Transmit voltage and display it until deep-sleep
+  if (ttn.sendBytes(&payload, sizeof(payload))) {
+    Heltec.display->drawString(0, 22, "Current Voltage: " + String((float)payload / 10) + "V");
+  }
+  Heltec.display->display();
+
+  // Make sure our transactions is handled before going to sleep
+  ttn.waitForPendingTransactions();
+}
+
+void setup() {
+  Heltec.begin(true /* DisplayEnable */, false /* LoRaEnable */, true /* SerialEnable */, false /* PABOOST */, BAND /* long BAND */);
+
+  analogReadResolution(12);
+
+  // Initialize display for usage
+  Heltec.display->init();
+  Heltec.display->flipScreenVertically();
+  Heltec.display->setFont(ArialMT_Plain_10);
+  Heltec.display->clear();
+
+  // Join TTN and reset counters
+  Serial.println("Starting TTN");
+  ttn.begin();
+  ttn.join(devEui, appEui, appKey);
+
+  // Wait for join to be completed
+  Heltec.display->clear();
+  Heltec.display->drawString(0, 0, "Joining TTN:");
+  Heltec.display->display();
+  int x = 60;
+  while (!ttn.isJoined()) {
+    Heltec.display->drawString(x, 0, ".");
+    Heltec.display->display();
+    delay(250);
+    x++;
+  }
+  Heltec.display->clear();
+  Heltec.display->drawString(0, 0, "TTN Connection online...");
+  Heltec.display->display();
+
+  // Add connection info
+  Serial.println("Setup done");
+  Heltec.display->clear();
+  Heltec.display->drawString(0, 0, "TTN Connection online...");
+}

src/main.h

@@ -0,0 +1,7 @@
+#ifndef MAIN_H_INCLUDED
+#define MAIN_H_INCLUDED
+
+float readVoltage();
+void sendVoltage(uint8_t payload);
+
+#endif