From bf974ab871e3be2eabb46be61e1934b8237e16a8 Mon Sep 17 00:00:00 2001
From: Daniel Friesel <derf@finalrewind.org>
Date: Tue, 21 Dec 2021 22:01:43 +0100
Subject: [PATCH] arduino nano adc: add getPin_mV function
---
include/arch/arduino-nano/driver/adc.h | 1 +
src/arch/arduino-nano/driver/adc.cc | 36 ++++++++++++++++++++++++++
2 files changed, 37 insertions(+)
diff --git a/include/arch/arduino-nano/driver/adc.h b/include/arch/arduino-nano/driver/adc.h
index 30ac338..c89f915 100644
--- a/include/arch/arduino-nano/driver/adc.h
+++ b/include/arch/arduino-nano/driver/adc.h
@@ -17,6 +17,7 @@ class AVRADC {
int16_t getTemp_mdegC(int16_t offset = 205);
uint16_t getVCC_mV();
+ uint16_t getPin_mV(uint8_t pin, uint16_t avcc = 0);
};
extern AVRADC adc;
diff --git a/src/arch/arduino-nano/driver/adc.cc b/src/arch/arduino-nano/driver/adc.cc
index 17cfc27..8f828a4 100644
--- a/src/arch/arduino-nano/driver/adc.cc
+++ b/src/arch/arduino-nano/driver/adc.cc
@@ -8,6 +8,42 @@
#include "arch.h"
#include "driver/adc.h"
+uint16_t AVRADC::getPin_mV(uint8_t pin, uint16_t avcc)
+{
+ if (avcc) {
+ // measure with AVCC reference
+ ADMUX = _BV(REFS0) | pin;
+ } else {
+ // measure with internal 1.1V bandgap refernce
+ ADMUX = _BV(REFS1) | _BV(REFS0) | pin;
+ }
+
+ // Enable ADC with /64 prescaler
+ ADCSRA = _BV(ADEN) | _BV(ADPS2);
+
+ // Wait for bandgap to stabilise (70us according to datasheet table 28-3)
+ arch.delay_ms(1);
+
+ // Start conversion
+ ADCSRA |= _BV(ADSC);
+
+ // wait until conversion is complete
+ while (ADCSRA & _BV(ADSC)) ;
+
+ uint8_t adcr_l = ADCL;
+ uint8_t adcr_h = ADCH;
+ uint16_t adcr = adcr_l + (adcr_h << 8);
+
+ // Disable ADC
+ ADCSRA &= ~_BV(ADEN);
+
+ if (avcc) {
+ return (uint32_t)avcc * adcr / 1023L;
+ } else {
+ return 1100L * adcr / 1023L;
+ }
+}
+
int16_t AVRADC::getTemp_mdegC(int16_t offset)
{
// Measure temperature probe with 1.1V bandgap reference
--
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