feat: automatic brightness adjustment

README.md

@@ -95,3 +95,16 @@ Leaving...
 Hard resetting via RTS pin...
 =================================================== [SUCCESS] Took 23.76 seconds ====================================================
 ```
+
+## Automatic Brightness Adjustment
+
+You can attach a voltage divider with a photo resistor as pull-down and a regular resistor as pull-up to the ESP's8266 ADC.
+If you choose to do this, please check the ADC voltage level of your ESP8266 board:  While the ADC itself works in the range 0.0V...1.0V, a lot of breakout boards scale that up to 0.0V...3.3V.
+
+Example with a NodeMCU board:
+
+![brightness.png][brightness.png]
+
+You can use the values `ADC_MAX`, `ADC_MIN`, `BRIGHT_MIN` and `BRIGHT_MAX` at the top of the file `esp/src/main.cpp` to fine-tune the sensitivity and thresholds of the auto adjustment.
+
+If you do not use this feature, and observe some flickering, please short the ADC to GND.

esp/src/main.cpp

@@ -6,6 +6,11 @@
 
 Adafruit_NeoPixel pixels(60, 5, NEO_GRB + NEO_KHZ800);
 
+uint16_t ADC_MAX = 900;
+uint16_t ADC_MIN = 250;
+uint8_t ADC_INVERT = 1;
+uint8_t BRIGHT_MIN = 50;
+uint8_t BRIGHT_MAX = 255;
 
 const char *ssid     = put your ssid here;
 const char *password = put your psk here;
@@ -34,6 +39,15 @@ uint8_t sixtyToPixel(int8_t sixty) {
 
 void loop() {
   delay(1000);
+  uint16_t brightness = analogRead(A0);
+  uint8_t bscale = (uint8_t) (255*(min(max(brightness, ADC_MIN), ADC_MAX) - ADC_MIN) / (ADC_MAX - ADC_MIN));
+  if (ADC_INVERT) {
+    bscale = 255 - bscale;
+  }
+  bscale = min(max(bscale, BRIGHT_MIN), BRIGHT_MAX);
+  Serial.print(brightness);
+  Serial.print(" -> ");
+  Serial.println(bscale);
   ntp.update();
   Serial.println(ntp.formattedTime("%T"));
   uint8_t h = sixtyToPixel((ntp.hours() % 12) * 5 + (ntp.minutes() / 12));
@@ -42,10 +56,10 @@ void loop() {
   uint8_t m = sixtyToPixel(ntp.minutes());
   uint8_t s = sixtyToPixel(ntp.seconds());
   pixels.clear();
-  pixels.setPixelColor(hl, pixels.getPixelColor(hl) | 0x00ff0000);
-  pixels.setPixelColor(h, pixels.getPixelColor(h) | 0x00ff0000);
-  pixels.setPixelColor(hr, pixels.getPixelColor(hr) | 0x00ff0000);
-  pixels.setPixelColor(m, pixels.getPixelColor(m) | 0x0000ff60);
-  pixels.setPixelColor(s, pixels.getPixelColor(s) | 0x000000ff);
+  pixels.setPixelColor(hl, pixels.getPixelColor(hl) | (bscale << 16));
+  pixels.setPixelColor(h, pixels.getPixelColor(h) | (bscale << 16));
+  pixels.setPixelColor(hr, pixels.getPixelColor(hr) | (bscale << 16));
+  pixels.setPixelColor(m, pixels.getPixelColor(m) | (bscale << 8) | (bscale >> 2));
+  pixels.setPixelColor(s, pixels.getPixelColor(s) | bscale);
   pixels.show();
 }