Poll ADC mode bit until conversion has finished

src/bus/i2c.c

@@ -21,6 +21,7 @@
 
 // TODO: Error handling and recovery besides watchdog timer.
 // TODO: Add more documentation from the atmel data sheet.
+// TODO: ADS1115 continuous mode instead of single-shot?
 // TODO: Implement TWI_vect ISR? This may not actually be
 // much better than the blocking approach.
 
@@ -31,6 +32,7 @@ static void  I2C_AHT20_Trigger(void);
 
 static int   I2C_ADS1115_WriteRegister(byte reg, word data);
 static word  I2C_ADS1115_ReadRegister(byte reg);
+static bool  I2C_ADS1115_IsReady(void);
 
 int I2C_Init(void)
 {
@@ -464,10 +466,21 @@ static word I2C_ADS1115_ReadRegister(byte reg)
 	return data[0] << 8 | data[1];
 }
 
+static bool I2C_ADS1115_IsReady(void)
+{
+	word reg;
+
+	Sleep(20);
+
+	reg = I2C_ADS1115_ReadRegister(0x01);
+
+	return reg & BIT(15);
+}
+
 word I2C_ADS1115_Read(int channel)
 {
 	word config;
-	word rate, gain, mux, os;
+	word os, mode, rate, gain, mux;
 
 	// Operational status or single-shot conversion
 	// start: This bit determines the operational
@@ -482,7 +495,15 @@ word I2C_ADS1115_Read(int channel)
 	// 0 : Device is performing a conversion
 	// 1 : Device is not performing a conversion
 
-	os = 0x8000; // Start single  |  10000000 00000000
+	os = 0x8000; // Start single   |  10000000 00000000
+
+	// Device operating mode: This bit controls the
+	// operating mode.
+
+	// 0 : Continuous-conversion mode
+	// 1 : Single-shot mode or power-down state
+
+	mode = 0x0100; // Single-shot  |  00000001 00000000
 
 	// Data rate: These bits control the data rate setting.
 
@@ -495,7 +516,7 @@ word I2C_ADS1115_Read(int channel)
 	// 110  |  475 SPS
 	// 111  |  860 SPS
 
-	rate = 0x0080; // 128 SPS     |  00000000 10000000
+	rate = 0x0080; // 128 SPS      |  00000000 10000000
 
 	// Programmable gain amplifier configuration: These
 	// bits set the FSR of the programmable gain amplifier.
@@ -509,7 +530,7 @@ word I2C_ADS1115_Read(int channel)
 	// 110  |  ±0.256 V
 	// 111  |  ±0.256 V
 
-	gain = 0x0000; // 6.144 V     |  00000100 00000000
+	gain = 0x0000; // 6.144 V      |  00000100 00000000
 
 	// Input multiplexer configuration: These bits
 	// configure the input multiplexer.
@@ -525,18 +546,21 @@ word I2C_ADS1115_Read(int channel)
 
 	mux = 0;
 	if (channel == ADS01)
-		mux = 0x4000; //     |  01000000 00000000
+		mux = 0x4000; //      |  01000000 00000000
 	else if (channel == ADS02)
-		mux = 0x5000; //     |  01010000 00000000
+		mux = 0x5000; //      |  01010000 00000000
 	else if (channel == ADS03)
-		mux = 0x6000; //     |  01100000 00000000
+		mux = 0x6000; //      |  01100000 00000000
 	else if (channel == ADS04)
-		mux = 0x7000; //     |  01110000 00000000
+		mux = 0x7000; //      |  01110000 00000000
 
-	// Single-shot conversion, active low, continous mode
-	config = os | rate | gain | mux;
+	// Single-shot conversion, active low
+	config = os | mode | rate | gain | mux;
 	I2C_ADS1115_WriteRegister(0x01, config);
 
+	// Wait until conversion finished
+	while (!I2C_ADS1115_IsReady());
+
 	return I2C_ADS1115_ReadRegister(0x00);
 }