Added further information to the readme

README.md

@@ -3,8 +3,31 @@
 A tiny tank cooler.
 
 Used components:
+----------------
 
-Arduino nano
+Arduino nano (old bootloader)
 PC fan 120mm 5V
 PWM D4184 MOS breakout board
 USB-C connector
+
+Connections:
+------------
+
+USB-C D+ <-> Pin4 CH430 chip
+USB-C D- <-> Pin5 CH430 chip
+
+VIN      <-> PWM board (+)
+VIN      <-> USB-C V+
+
+GND      <-> USB-C GND
+GND      <-> BMP280 breakout board GND
+GND      <-> PWM breakout board GND
+
+D9       <-> PWM Pin of the breakout board
+
+A4       <-> SCL pin of BMP280 breakout board
+A5       <-> SDA pin of BMP280 breakout board
+
+PWM board load <-> PC fan (+)
+PWM board GNC  <-> PC fan (-)
+

firmware/firmware.ino

@@ -0,0 +1,73 @@
+
+#define FAN_PIN    9 // D9
+#define L_LED_PIN 13 // D13
+
+#define BMP280_I2C_ADDRESS 0x76  // BMP280 conneciton: D1 = SCL; D2 = SDA
+
+// minimum value to start both fan's is 110
+// without queeking noise is 255
+#define FAN_ON_TEMP      26.0
+#define FAN_OFF_MAX_TEMP 25.0
+
+#define FAN_ON_STATE  HIGH
+#define FAN_OFF_STATE  LOW
+
+#define BMP280_CHECK_INTERVAL_MS 2000 // every 60000 = 60 seconds
+
+float bmp280_temp = -99.9;
+uint32_t bmp280_lastcheck_millis = BMP280_CHECK_INTERVAL_MS;
+
+uint8_t fan_state = LOW;
+
+float sensor_bmp280_temperature();
+
+void setup()
+{
+  // put your setup code here, to run once:
+
+  // setup serial
+  Serial.begin(115200);
+  Serial.println();
+  delay(1000);
+
+  // setup BMP280
+  Serial.println("Sensor BMP280 init status: " + String(sensor_bmp280_begin(BMP280_I2C_ADDRESS)));
+  bmp280_temp = sensor_bmp280_temperature();
+
+  // setup FAN Pin
+  pinMode(FAN_PIN, OUTPUT);
+
+  pinMode(L_LED_PIN, OUTPUT);
+}
+
+void loop()
+{
+  // put your main code here, to run repeatedly:
+
+  if ((bmp280_lastcheck_millis + BMP280_CHECK_INTERVAL_MS) <= millis())
+  {
+    bmp280_temp = sensor_bmp280_temperature();
+    Serial.println("Temperature: " + String(bmp280_temp) + "°C");
+    digitalWrite(L_LED_PIN, HIGH);
+
+    if (fan_state > 0 && bmp280_temp <= FAN_OFF_MAX_TEMP)
+    {
+      fan_state = FAN_OFF_STATE;  // off
+    }
+
+    if (bmp280_temp >= FAN_ON_TEMP)
+    {
+      fan_state = FAN_ON_STATE;
+    }
+
+    Serial.println("FAN state: " + String(fan_state));
+
+    digitalWrite(FAN_PIN, fan_state);
+
+    digitalWrite(L_LED_PIN, LOW);
+
+    bmp280_lastcheck_millis = millis();
+  }
+
+}
+

firmware/sensor_bmp280.ino

@@ -0,0 +1,39 @@
+
+#include <Adafruit_BMP280.h>  // Install from library manager - sensor board info: https://www.bastelgarage.ch/bmp280-temperatur-luftdruck-sensor
+
+Adafruit_BMP280 _sensor_bmp280;
+Adafruit_Sensor *_sensor_bmp280_temp = _sensor_bmp280.getTemperatureSensor();
+Adafruit_Sensor *_sensor_bmp280_pressure = _sensor_bmp280.getPressureSensor();
+
+#define BPM280_TEMP_FACTOR 1.0
+
+bool sensor_bmp280_begin(uint8_t addr) {
+  bool status = _sensor_bmp280.begin(addr);
+
+  if (status) {
+    Serial.println("BMP280 Connected");
+
+    _sensor_bmp280.setSampling(Adafruit_BMP280::MODE_NORMAL,     /* Operating Mode. */
+                               Adafruit_BMP280::SAMPLING_X2,     /* Temp. oversampling */
+                               Adafruit_BMP280::SAMPLING_X16,    /* Pressure oversampling */
+                               Adafruit_BMP280::FILTER_X16,      /* Filtering. */
+                               Adafruit_BMP280::STANDBY_MS_500); /* Standby time. */
+
+  } else {
+    Serial.println("Could not find a valid BMP280 sensor, check wiring or try a different address!");
+    Serial.println("SensorID was: " + String(_sensor_bmp280.sensorID()));
+    Serial.println("  ID of 0xFF probably means a bad address, a BMP180 or BMP085");
+    Serial.println("  ID of 0x56-0x58 represents a BMP280,");
+    Serial.println("  ID of 0x60 represents a BME280,");
+    Serial.println("  ID of 0x61 represents a BME680.");
+  }
+
+  return status;
+}
+
+float sensor_bmp280_temperature() {
+  sensors_event_t temp_event, pressure_event;
+  _sensor_bmp280_temp->getEvent(&temp_event);
+  return temp_event.temperature * BPM280_TEMP_FACTOR;
+}
+