implement ads1015 driver (#2458)

* first approximation of ads1015

* fix ads

* misc

* comment

Co-authored-by: Matthew Kennedy <makenne@microsoft.com>

firmware/hw_layer/adc/ads1015.cpp

@@ -0,0 +1,65 @@
+#include "ads1015.h"
+#include "efilib.h"
+
+constexpr uint8_t addr = 0x48;
+
+#define ADS1015_CONV (0)
+#define ADS1015_CONFIG (1)
+#define ADS1015_LO_THRESH (2)
+#define ADS1015_HI_THRESH (3)
+
+bool Ads1015::init(brain_pin_e scl, brain_pin_e sda) {
+	m_i2c.init(scl, sda);
+
+	// ADS1015 has no ID register - so we read the Lo_thresh instead
+	uint16_t loThresh = readReg(ADS1015_LO_THRESH);
+
+	if (loThresh != 0x8000) {
+		return false;
+	}
+
+	m_hasInit = true;
+	return true;
+}
+
+void Ads1015::readChannels(float (&result)[4]) {
+	for (size_t i = 0; i < 4; i++) {
+		result[i] = readChannel(i);
+	}
+}
+
+float Ads1015::readChannel(uint8_t ch) {
+	// set the channel
+	// set to +-6.144v full scale, fastest sampling, manual conversion start
+	writeReg(ADS1015_CONFIG, 0xC1E0 | ch << 12);
+
+	// Wait for conversion to complete
+	// Bit is cleared while conversion is ongoing, set when done
+	while ((readReg(ADS1015_CONFIG) & 0x8000) == 0) ;
+
+	// Read the result
+	int16_t result = readReg(ADS1015_CONV);
+	// Result is 12 bits left aligned, so right align the result
+	result = result >> 4;
+
+	// 2048 counts = positive 6.144 volts
+	constexpr float ratio = 6.144f / 2048;
+	return result * ratio;
+}
+
+void Ads1015::writeReg(uint8_t reg, uint16_t data) {
+	uint8_t packet[3];
+
+	packet[0] = reg;
+	packet[1] = data >> 8;
+	packet[2] = data & 0xFF;
+
+	m_i2c.write(addr, packet, 3);
+}
+
+uint16_t Ads1015::readReg(uint8_t reg) {
+	uint16_t res;
+	m_i2c.write(addr, &reg, 1);
+	m_i2c.read(addr, reinterpret_cast<uint8_t*>(&res), 2);
+	return SWAP_UINT16(res);
+}

firmware/hw_layer/adc/ads1015.h

@@ -0,0 +1,18 @@
+#pragma once
+
+#include "i2c_bb.h"
+
+class Ads1015 {
+public:
+	bool init(brain_pin_e scl, brain_pin_e sda);
+	void readChannels(float (&result)[4]);
+
+private:
+	float readChannel(uint8_t ch);
+
+	void writeReg(uint8_t reg, uint16_t data);
+	uint16_t readReg(uint8_t reg);
+
+	bool m_hasInit = false;
+	BitbangI2c m_i2c;
+};

firmware/hw_layer/hw_layer.mk

@@ -31,6 +31,7 @@ HW_LAYER_EMS_CPP = $(HW_LAYER_EGT_CPP) \
 	$(PROJECT_DIR)/hw_layer/lcd/lcd_HD44780.cpp \
 	$(PROJECT_DIR)/hw_layer/adc/adc_inputs.cpp \
 	$(PROJECT_DIR)/hw_layer/adc/adc_subscription.cpp \
+	$(PROJECT_DIR)/hw_layer/adc/ads1015.cpp \
 	$(PROJECT_DIR)/hw_layer/sensors/hip9011.cpp \
 	$(PROJECT_DIR)/hw_layer/sensors/hip9011_logic.cpp \
 	$(PROJECT_DIR)/hw_layer/mc33816.cpp \

firmware/hw_layer/i2c_bb.cpp

@@ -188,8 +188,11 @@ void BitbangI2c::writeRead(uint8_t addr, const uint8_t* writeData, size_t writeS
 	for (size_t i = 0; i < writeSize; i++) {
 		writeByte(writeData[i]);
 	}
-	
-	// Send a repeated start bit to indicate transition to read
+
+	read(addr, readData, readSize);
+}
+
+void BitbangI2c::read(uint8_t addr, uint8_t* readData, size_t readSize) {
 	start();
 
 	// Address + read

firmware/hw_layer/i2c_bb.h

@@ -23,6 +23,8 @@ public:
 
 	// Write a sequence of bytes to the specified device
 	void write(uint8_t addr, const uint8_t* data, size_t size);
+	// Read a sequence of bytes from the device
+	void read(uint8_t addr, uint8_t* data, size_t size);
 	// Write some bytes then read some bytes back after a repeated start bit
 	void writeRead(uint8_t addr, const uint8_t* writeData, size_t writeSize, uint8_t* readData, size_t readSize);