analog.c: trim down analog values storage.

Saves 10 bytes RAM and 16 bytes binary size on an 1284P (8 ADC
channels) running two sensors. Should also be a bit faster, as one
loop runs fewer iterations.

Also, checking for NUM_TEMP_SENSORS was a mistake, as temp sensors
_not_ using an analog pin exist. Extreme case is, temp sensors
exist, but zero ADC channels are used.

analog.c

@@ -12,34 +12,31 @@
 /* OR-combined mask of all channels */
 #undef DEFINE_TEMP_SENSOR
 //! automagically generate analog_mask from DEFINE_TEMP_SENSOR entries in config.h
-#define DEFINE_TEMP_SENSOR(name, type, pin, additional) | (((type == TT_THERMISTOR) || (type == TT_AD595)) ? (1 << (pin ## _ADC)) : 0)
-
+#define DEFINE_TEMP_SENSOR(name, type, pin, additional) \
+	| (((type == TT_THERMISTOR) || (type == TT_AD595)) ? (1 << (pin ## _ADC)) : 0)
 #ifdef	AIO8_PIN
 	static const uint16_t analog_mask = 0
 #else
 	static const uint8_t analog_mask = 0
 #endif
-
 #include "config.h"
 ;
 #undef DEFINE_TEMP_SENSOR
 
-#ifdef AIO8_PIN
-	#define	AINDEX_MASK	0x1F
-	#define	AINDEX_MAX 15
-	#define	AINDEX_CURRENT ((ADMUX & 0x07) | ((ADCSRB & MASK(MUX5))?0x08:0))
-#else
-	#define	AINDEX_MASK	0x0F
-	#define	AINDEX_MAX 7
-	#define	AINDEX_CURRENT (ADMUX & 0x07)
-#endif
-
 static uint8_t adc_counter;
-static volatile uint16_t adc_result[AINDEX_MAX + 1] __attribute__ ((__section__ (".bss")));
+static volatile uint16_t adc_result[NUM_TEMP_SENSORS] __attribute__ ((__section__ (".bss")));
+
+#define DEFINE_TEMP_SENSOR(name, type, pin, additional) \
+	((type == TT_THERMISTOR) || (type == TT_AD595)) ? (pin ## _ADC) : 255,
+static uint8_t adc_channel[NUM_TEMP_SENSORS] =
+{
+  #include "config.h"
+};
+#undef DEFINE_TEMP_SENSOR
 
 //! Configure all registers, start interrupt loop
 void analog_init() {
-	if (NUM_TEMP_SENSORS > 0) {
+	if (analog_mask > 0) {
 		// clear ADC bit in power reduction register because of ADC use.
 		#ifdef	PRR
 			PRR &= ~MASK(PRADC);
@@ -84,24 +81,21 @@ ISR(ADC_vect, ISR_NOBLOCK) {
 	uint8_t sreg_save = SREG;
 
 	// emulate free-running mode but be more deterministic about exactly which result we have, since this project has long-running interrupts
-	if (NUM_TEMP_SENSORS > 0) {
+	if (analog_mask > 0) { // at least one temp sensor uses an analog channel
 		// store next result
-		adc_result[AINDEX_CURRENT] = ADC;
+		adc_result[adc_counter] = ADC;
 
-		// find next channel
-		/* TODO: this is not exactly high performance. adc_result[] should be of
-		   size NUM_TEMP_SENSORS only, along with an array of the corresponding
-		   ADC channel(s). This also requires changes to the callers of
-		   analog_read(). */ 
+		// next channel
 		do {
 			adc_counter++;
-			adc_counter &= AINDEX_MAX;
-		} while ((analog_mask & (1 << adc_counter)) == 0);
+			if (adc_counter >= sizeof(adc_channel))
+				adc_counter = 0;
+		} while (adc_channel[adc_counter] == 255);
 
 		// start next conversion
-		ADMUX = (adc_counter & 0x07) | REFERENCE;
+		ADMUX = (adc_channel[adc_counter] & 0x07) | REFERENCE;
 		#ifdef	MUX5
-			if (adc_counter & 0x08)
+			if (adc_channel[adc_counter] & 0x08)
 				ADCSRB |= MASK(MUX5);
 			else
 				ADCSRB &= ~MASK(MUX5);
@@ -120,8 +114,8 @@ ISR(ADC_vect, ISR_NOBLOCK) {
 	\param channel Channel to be read
 	\return analog reading, 10-bit right aligned
 */
-uint16_t	analog_read(uint8_t channel) {
-	if (NUM_TEMP_SENSORS > 0) {
+uint16_t	analog_read(uint8_t index) {
+	if (analog_mask > 0) {
 		uint16_t r;
 
 		uint8_t sreg;
@@ -131,7 +125,7 @@ uint16_t	analog_read(uint8_t channel) {
 		cli();
 
 		// atomic 16-bit copy
-		r = adc_result[channel];
+		r = adc_result[index];
 
 		// restore interrupt flag
 		SREG = sreg;

analog.h

@@ -27,6 +27,6 @@
 
 void 			analog_init(void);
 
-uint16_t	analog_read(uint8_t channel);
+uint16_t	analog_read(uint8_t index);
 
 #endif	/* _ANALOG_H */

temp.c

@@ -178,7 +178,7 @@ void temp_sensor_tick() {
 					do {
 						uint8_t j, table_num;
 						//Read current temperature
-						temp = analog_read(temp_sensors[i].temp_pin);
+						temp = analog_read(i);
 						// for thermistors the thermistor table number is in the additional field
 						table_num = temp_sensors[i].additional;
 
@@ -237,7 +237,7 @@ void temp_sensor_tick() {
 
 				#ifdef	TEMP_AD595
 				case TT_AD595:
-					temp = analog_read(temp_sensors[i].temp_pin);
+					temp = analog_read(i);
 
 					// convert
 					// >>8 instead of >>10 because internal temp is stored as 14.2 fixed point