battery voltage, move display around

1 files changed, 38 insertions, 0 deletions

diff --git a/battery.h b/battery.h
new file mode 100644
index 0000000..825a3ab
--- /dev/null
+++ b/battery.h
@@ -0,0 +1,38 @@
+#pragma once
+#include <Arduino.h>
+
+/*
+  code inspired by https://gist.github.com/jenschr/dfc765cb9404beb6333a8ea30d2e78a1
+ */
+
+class Battery {
+  uint8_t pin;
+public:
+  /*
+    the schematics at
+    https://github.com/Xinyuan-LilyGO/LilyGo-T5-Epaper-Series/tree/master/schematic
+    show a voltage divider connected to pin 35
+  */
+  Battery(uint8_t _pin=35) : pin(_pin) {};
+  float voltage() {
+    /*
+      Comment from the gist:
+
+      The ADC value is a 12-bit number, so the maximum value is 4095
+      (counting from 0).
+
+      To convert the ADC integer value to a real voltage you’ll need
+      to divide it by the maximum value of 4095, then double it (note
+      above that Adafruit halves the voltage), then multiply that by
+      the reference voltage of the ESP32 which is 3.3V and then
+      finally, multiply that again by the ADC Reference Voltage of
+      1100mV.
+
+      Comment from me: that assumes that ADC is linear, which is probably isn't
+
+      Also, the battery voltage is not a decent indicator of charge
+      level, but that's what I've got
+    */
+    return (float)(analogRead(pin)) / 4095*2*3.3*1.1;
+  }
+};