Freeze

sbc_fw/adc.cpp

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+/*
+ * @file adc.cpp
+ * @brief
+ *
+ * Created: 27.09.2025 05:06:33
+ * Author: ThePetrovich
+ *
+ * Copyright YKSA - Sakha Aerospace Systems, LLC.
+ * See the LICENSE file for details.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "adc.h"
+#include "config.h"
+#include "utils.h"
+#include <Arduino.h>
+#include <util/atomic.h>
+
+uint8_t adc_flags = 0;
+
+int16_t adc_to_temperature_c(uint16_t adc_value)
+{
+	// MCP9700: 500 mV at 0°C, 10 mV per degree, vref = 3.0V
+	// Result in 0.1°C units
+	uint16_t adc_resolution = ADC_RESOLUTION
+				  << config.flags.adc_oversample_bits; // Adjust resolution based on oversampling
+	return (int16_t)((adc_value * ADC_VREF_MV / adc_resolution - config.tempcal));
+}
+
+uint16_t adc_to_voltage_mv(uint16_t adc_value) { return (uint16_t)(adc_value * VOLTAGE_MV_PER_STEP); }
+
+uint16_t adc_read_oversampled(uint8_t pin, uint8_t samples)
+{
+	uint32_t sum = 0;
+
+	// unrolled loop
+	uint8_t shift = ((samples == 64) ? 3 : (samples == 16) ? 2 : (samples == 4) ? 1 : 0);
+
+	for (uint8_t i = 0; i < samples; i++) {
+		sum += analogRead(pin);
+	}
+
+	return (uint16_t)(sum >> shift);
+}
+
+void adc_enable_fast(void)
+{
+	ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+	{
+		ADC0.CTRLA |= ADC_ENABLE_bm;
+
+		// Enable oversampling x16 for 12-bit result
+		ADC0.CTRLB |= (config.flags.adc_oversample_bits << 2); // 2, 4, or 6 for 4x, 16x, or 64x oversampling
+
+		ADC0.CTRLC = 0;						// reset
+		ADC0.CTRLC |= ADC_PRESC_DIV32_gc | ADC_REFSEL_VREFA_gc; // CLK_PER/32, VREFA as reference
+
+		ADC0.EVCTRL |= ADC_STARTEI_bm; // EVSYS input to start conversion
+		ADC0.INTCTRL |= ADC_RESRDY_bm; // Enable interrupt on conversion complete
+
+		// Configure VREF, Microchip DS40002015B page 424
+		VREF.CTRLA |= VREF_ADC0REFSEL_4V34_gc;
+
+		ADC0.MUXPOS = ADC_MUXPOS_AIN3_gc; // DET_SIG_PIN
+
+		adc_flags |= 0x01; // Fast mode enabled
+	}
+}
+
+void adc_restore_default(void)
+{
+	ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+	{
+		// Disable oversampling
+		ADC0.CTRLB &= ~ADC_SAMPNUM_gm;
+
+		ADC0.CTRLC &= ~ADC_REFSEL_gm;
+		ADC0.CTRLC |= ADC_REFSEL_VREFA_gc; // VREFA as reference
+
+		ADC0.EVCTRL &= ~ADC_STARTEI_bm;
+		ADC0.INTCTRL &= ~ADC_RESRDY_bm;
+
+		adc_flags &= ~0x01; // Fast mode disabled
+	}
+}
+
+static uint16_t adc_conversion(void)
+{
+	ADC0.COMMAND = ADC_STCONV_bm;
+	while (!(ADC0.INTFLAGS & ADC_RESRDY_bm))
+		;
+	return ADC0.RES;
+}
+
+static uint16_t adc_read_tempsense(void)
+{
+	/* DS40002015B-page 425
+	    1. Configure the internal voltage reference to 1.1V by configuring the VREF peripheral.
+	    2. Select the internal voltage reference by writing the REFSEL bits in ADCn.CTRLC to 0x0.
+	    3. Select the ADC temperature sensor channel by configuring the MUXPOS register
+	    (ADCn.MUXPOS). This enables the temperature sensor.
+	    5. In ADCn.SAMPCTRL select INITDLY ≥ 32 µs × CLK_ADC
+	    6. In ADCn.CTRLC select SAMPLEN ≥ 32 µs × CLK_ADC
+	    7. Acquire the temperature sensor output voltage by starting a conversion.
+	    8. Process the measurement result as described below.
+	*/
+	ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+	{
+		ADC0.CTRLA |= ADC_ENABLE_bm;
+
+		ADC0.CTRLB |= ADC_SAMPNUM_ACC16_gc;
+
+		ADC0.CTRLC = 0; // reset
+		ADC0.CTRLC |= ADC_PRESC_DIV32_gc | ADC_REFSEL_INTREF_gc;
+
+		// Configure VREF, Microchip DS40002015B page 424
+		VREF.CTRLA |= VREF_ADC0REFSEL_1V1_gc;
+
+		// Select temperature sensor channel
+		ADC0.MUXPOS = ADC_MUXPOS_TEMPSENSE_gc;
+	}
+
+	delay(10);
+
+	int8_t sigrow_offset = SIGROW.TEMPSENSE1; // Read signed value from signature row
+	uint8_t sigrow_gain = SIGROW.TEMPSENSE0;
+	// Read unsigned value from signature row
+	uint16_t adc_reading = adc_conversion() >> 4;
+	// ADC conversion result with 1.1 V internal reference
+	uint32_t temp = adc_reading - sigrow_offset;
+	temp *= sigrow_gain; // Result might overflow 16 bit variable (10bit+8bit)
+	temp += 0x80;
+	// Add 1/2 to get correct rounding on division below
+	temp >>= 8;
+	// Divide result to get Kelvin
+	uint16_t temperature_in_K = temp;
+
+	adc_restore_default();
+
+	if (adc_flags & 0x01) {
+		adc_enable_fast();
+	}
+
+	return temperature_in_K;
+}
+
+void adc_cmd_calibrate(void)
+{
+	ATOMIC_BLOCK(ATOMIC_RESTORESTATE)
+	{
+		ADC0.EVCTRL &= ~ADC_STARTEI_bm; // Start event input
+		ADC0.INTCTRL &= ~ADC_RESRDY_bm;
+
+		ADC0.CTRLB |= ADC_SAMPNUM_ACC16_gc; // 16 samples for oversampling to get 12-bit result from 10-bit ADC
+
+		ADC0.CTRLC = 0;						 // reset
+		ADC0.CTRLC |= ADC_PRESC_DIV32_gc | ADC_REFSEL_VDDREF_gc; // CLK_PER/32, VDD as reference
+
+		// Configure VREF, Microchip DS40002015B page 424
+		VREF.CTRLA |= VREF_ADC0REFSEL_4V34_gc;
+	}
+
+	delay(10); // Wait for VREF to stabilize
+
+	// set MUX to gnd and read offset
+	ADC0.MUXPOS = ADC_MUXPOS_GND_gc;
+	delay(1);
+	uint16_t offset = adc_conversion() >> 2; // 12-bit result
+
+	Serial.write(offset & 0xFF);
+	Serial.write(offset >> 8);
+
+	if (config.adccal0 == 0xFFFF) {
+		config.adccal0 = offset;
+	}
+
+	// set MUX to external AREF and read 3.0V value
+	ADC0.MUXPOS = ADC_MUXPOS_AIN7_gc; // AREF pin
+	delay(1);
+
+	uint16_t aref = adc_conversion() >> 2; // 12-bit result
+
+	Serial.write(aref & 0xFF);
+	Serial.write(aref >> 8);
+
+	if (config.adccal3 == 0xFFFF) {
+		config.adccal3 = aref;
+	}
+
+	// set MUX to DACREF0 and read
+	ADC0.MUXPOS = ADC_MUXPOS_DACREF_gc;
+	delay(1);
+
+	uint16_t dacref = adc_conversion() >> 2; // 12-bit result
+	Serial.write(dacref & 0xFF);
+	Serial.write(dacref >> 8);
+
+	uint16_t tempsense = adc_read_tempsense();
+	Serial.write(tempsense & 0xFF);
+	Serial.write(tempsense >> 8);
+
+	Serial.write(SIGROW.TEMPSENSE1);
+	Serial.write(SIGROW.TEMPSENSE0);
+
+	Serial.flush();
+	SERIAL_BUFFER_CLEAR();
+
+	adc_restore_default();
+
+	if (adc_flags & 0x01) {
+		adc_enable_fast();
+	}
+}