From 0fb1be4440b17f889614479ce15fdf2d2e8e193a Mon Sep 17 00:00:00 2001
From: Thomas von Dein <tom@izb.net>
Date: Mon, 2 Mar 2020 21:27:34 +0100
Subject: [PATCH] testing Vbg reading

---
 .../SensorSerial.ino                          | 23 ++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/841-tinycore-micronucleus-bme280-spi-radio-test/SensorSerial.ino b/841-tinycore-micronucleus-bme280-spi-radio-test/SensorSerial.ino
index d1f7d8e..4c28f2b 100644
--- a/841-tinycore-micronucleus-bme280-spi-radio-test/SensorSerial.ino
+++ b/841-tinycore-micronucleus-bme280-spi-radio-test/SensorSerial.ino
@@ -31,6 +31,8 @@ SDO/MISO PA5          PA6 SDI/MOSI
   
  */
 
+#include <avr/io.h>
+
 #define TINY_BME280_SPI
 #include <TinyBME280.h>
 
@@ -45,6 +47,7 @@ SDO/MISO PA5          PA6 SDI/MOSI
 
 static tiny::BME280 sensor;
 RFTransmitter transmitter(OUTPUT_PIN, NODE_ID);
+const long InternalReferenceVoltage = 1083L;
 
 #define SET_OUTPUT(pin) DDRB  |=  (1 << pin)
 #define SET_HIGH(pin)   PORTB |=  (1 << pin)
@@ -84,8 +87,6 @@ void print_measurements() {
   print_asufloat(humidity, 1000);
   Serial.println(" %");
 
-  Serial.println();
-
   transmitter.send((byte *)temp, sizeof(temp));
   SET_HIGH(LED);
 }
@@ -94,10 +95,26 @@ void halt() {
   while(1);
 }
 
+void print_voltage() {
+  int value;
+  ADCSRA |= _BV( ADSC );
+  while( ( (ADCSRA & (1<<ADSC)) != 0 ) );
+  value = (((InternalReferenceVoltage * 1024L) / ADC) + 5L) / 10L;
+  Serial.print("         Voltage: ");
+  Serial.println(value);
+  Serial.println();
+}
+
 void setup() {
   SET_OUTPUT(LED);
   Serial.begin(115200);
   Serial.println("init");
+  // Enable ADC
+  ADCSRA |= (1 << ADEN);
+  ADMUXB = (0<<REFS2) | (1<<REFS1) | (0<<REFS0);
+  ADMUXA = (0<<MUX5) | (0<<MUX4) | (0<<MUX3) | (0<<MUX2) | (0<<MUX1) | (1<<MUX0);
+  ADCSRB = (0<<ADLAR);
+  //analogReference( INTERNAL );
 
   if(sensor.beginSPI(CS) == false) {
     Serial.println("Sensor BME280 connect failed, check wiring!");
@@ -105,9 +122,9 @@ void setup() {
   }  
 }
 
-
 void loop() {
   print_measurements();
+  print_voltage();
   delay(DELAY);
 }