Arduino: Add ADC driver

2 files changed, 80 insertions, 0 deletions

diff --git a/src/arch/arduino-nano/Makefile.inc b/src/arch/arduino-nano/Makefile.inc
index ebc77ea..a664a30 100644
--- a/src/arch/arduino-nano/Makefile.inc
+++ b/src/arch/arduino-nano/Makefile.inc
@@ -37,6 +37,10 @@ else ifneq ($(findstring i2c,${arch_drivers}), )
 	CXX_TARGETS += src/arch/arduino-nano/driver/i2c.cc
 endif
 
+ifneq ($(findstring adc,${arch_drivers}), )
+	CXX_TARGETS += src/arch/arduino-nano/driver/adc.cc
+endif
+
 ifneq ($(findstring spi,${arch_drivers}), )
 	CXX_TARGETS += src/arch/arduino-nano/driver/spi.cc
 endif
diff --git a/src/arch/arduino-nano/driver/adc.cc b/src/arch/arduino-nano/driver/adc.cc
new file mode 100644
index 0000000..1583b15
--- /dev/null
+++ b/src/arch/arduino-nano/driver/adc.cc
@@ -0,0 +1,76 @@
+#include <avr/io.h>
+
+#include "arch.h"
+#include "driver/adc.h"
+
+int16_t AVRADC::getTemp_mdegC(int16_t offset)
+{
+	// Measure temperature probe with 1.1V bandgap reference
+	ADMUX = _BV(REFS1) |  _BV(REFS0) | 0x08;
+
+	// 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 for conversion to complete
+	while (ADCSRA & _BV(ADSC)) ;
+
+	// typical values: 242 mV @ -45 degC
+	// typical values: 314 mV @ +25 degC
+	// typical values: 380 mV @ +85 degC
+	// slope: 0.9090.. degC / mV at  25 .. 85 degC
+	// -> approx. 286.5 mV @ 0 degC / approx -260.45 degC @ 0 mV
+	// -> T[degC] = ADC[mV] * 0.91 - 261
+	// -> T[mdegC] = ADC[mV] * 91 - 26100
+	// slope: 0.9722.. mV / degC at -45 .. 25 degC
+	// slope: 0.942    mV / degC at -45 .. 85 degC
+	uint8_t adcr_l = ADCL;
+	uint8_t adcr_h = ADCH;
+	uint16_t adcr = adcr_l + (adcr_h << 8);
+	uint16_t vadc = 1100L * adcr / 1023L;
+
+	// adjust for chip-specific variations
+	vadc += offset;
+
+	int16_t temp_mdegc = vadc * 91 - 26100L;
+
+	// Disable ADC
+	ADCSRA &= ~_BV(ADEN);
+
+	return temp_mdegc;
+}
+
+uint16_t AVRADC::getVCC_mV()
+{
+	// Measure internal 1.1V bandgap using VCC as reference
+	ADMUX = _BV(REFS0) | 0x0e;
+
+	// 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 for conversion to complete
+	while (ADCSRA & _BV(ADSC)) ;
+
+	uint8_t adcr_l = ADCL;
+	uint8_t adcr_h = ADCH;
+	uint16_t adcr = adcr_l + (adcr_h << 8);
+	uint16_t vcc = 1100L * 1023 / adcr;
+
+	// Disable ADC
+	ADCSRA &= ~_BV(ADEN);
+
+	return vcc;
+}
+
+AVRADC adc;