Unverified Commit ff979a91 authored by Birte Kristina Friesel's avatar Birte Kristina Friesel
Browse files

lora32u4ii: Add ADC driver

parent 4f6973b8

include/arch/lora32u4ii/driver/adc.h

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#ifndef ADC_H

#define ADC_H



class AVRADC {

	private:

		AVRADC(AVRADC const &copy);



	public:

		AVRADC() {}



		int16_t getTemp_mdegC(int16_t offset = 205);

		uint16_t getVCC_mV();

		uint16_t getVBat_mV(bool controlCharger);

};



extern AVRADC adc;



#endif

include/arch/lora32u4ii/driver/gpio.h

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@@ -3,6 +3,14 @@ 


#include <avr/io.h>



/*

 * lora32u4ii v1.3 pin map:

 *

 * PB0 -> Charger and Vbat/2 measurement voltage divider enable

 * PB5 -> User LED

 * PB5 <- Vbat/2

 */



class GPIO {

	private:

		GPIO(const GPIO &copy);
@@ -40,7 +48,8 @@ class GPIO { 
		};



		inline void setup() {

			DDRB = _BV(PB5);

			// PB5 is both output (user LED) and input (Vbat/2 to ADC).

			// Leave it as input by default.

		}

		inline volatile uint8_t * pinToPort(uint8_t pin) {

			if (pin <= pb7) {

src/arch/lora32u4ii/Kconfig

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# Copyright 2021 Daniel Friesel

#

# SPDX-License-Identifier: CC0-1.0



config arch_lora32u4ii_cpufreq

int "CPU Frequency"

#!accept [62500, 125000, 250000, 500000, 1000000, 2000000, 4000000, 8000000]

range 62500 8000000

default 8000000

help

  Assumes an externel 8MHz crystal to be present



config arch_lora32u4ii_driver_adc

bool "ADC (Analog-Digital-Converter)"

select meta_driver_adc



config arch_lora32u4ii_driver_uptime

bool "Uptime Counter"

select meta_driver_uptime

src/arch/lora32u4ii/Makefile.inc

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@@ -44,8 +44,16 @@ ifeq (${timer_s}, 1) 
	CONFIG_arch_lora32u4ii_driver_uptime = y

endif



ifneq ($(findstring adc,${arch_drivers}), )

	CONFIG_arch_lora32u4ii_driver_adc = y

endif



# Kconfig driver selection



ifdef CONFIG_arch_lora32u4ii_driver_adc

	CXX_TARGETS += src/arch/lora32u4ii/driver/adc.cc

endif



ifdef CONFIG_arch_lora32u4ii_driver_uptime

	COMMON_FLAGS += -DTIMER_S

	CXX_TARGETS += src/arch/lora32u4ii/driver/uptime.cc

src/arch/lora32u4ii/driver/adc.cc

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#include <avr/io.h>



#include "arch.h"

#include "driver/adc.h"

#include "driver/gpio.h"



int16_t AVRADC::getTemp_mdegC(int16_t offset)

{

	// Measure temperature probe with internal 2.56V bandgap reference

	ADMUX = _BV(REFS1) |  _BV(REFS0) | 0x07;

	ADCSRB = _BV(MUX5);



	// Enable ADC with /64 prescaler

	ADCSRA = _BV(ADEN) | _BV(ADPS2) | _BV(ADPS1);



	// Wait for bandgap and temperature references to stabilise

	arch.delay_ms(1);



	// Start conversion

	ADCSRA |= _BV(ADSC);



	// Wait for conversion to complete

	while (ADCSRA & _BV(ADSC)) ;



	// TODO this is for atmega328p, not atmega32u4

	// 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) | 0x1e;

	ADCSRB = 0;



	// Enable ADC with /64 prescaler

	ADCSRA = _BV(ADEN) | _BV(ADPS2) | _BV(ADPS1);



	// Wait for bandgap to stabilise

	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;

}



uint16_t AVRADC::getVBat_mV(bool controlCharger)

{

	// Measure VBat/2 (via voltage divider on PB5 / ADC12) using VCC as reference.

	// Caution: PB5 is also connected to the white user LED.

	ADMUX = _BV(REFS0) | 0x04;

	ADCSRB = _BV(MUX5);



	// Enable ADC with /64 prescaler

	ADCSRA = _BV(ADEN) | _BV(ADPS2) | _BV(ADPS1);



	if (controlCharger) {

		// Turn on Vbat/2 voltage divider (and charger!)

		gpio.output(GPIO::pb0, 1);

	}



	// Wait for things to stabilise

	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 vbat = 4200L * adcr / 1023;



	// Disable ADC

	ADCSRA &= ~_BV(ADEN);



	if (controlCharger) {

		// Turn off voltage divider (and charger!)

		gpio.output(GPIO::pb0, 0);

	}



	return vbat;

}





AVRADC adc;