changes to tare, added debugEnable flag

HX711-multi.cpp

@@ -6,6 +6,8 @@ HX711MULTI::HX711MULTI(int count, byte *dout, byte pd_sck, byte gain) {
 	DOUT 	= dout; //TODO - make the input of dout to the function a const, or otherwise copy the values for local storage
 	COUNT   = count;
 
+	debugEnabled = false;
+
 	pinMode(PD_SCK, OUTPUT);
 	for (int i=0; i<count; i++) {
 		pinMode(DOUT[i], INPUT);
@@ -75,11 +77,11 @@ bool HX711MULTI::tare(byte times, uint16_t tolerance) {
 		minValues[i]=0x7FFFFFFF;
 		maxValues[i]=0x80000000;
 
-		OFFSETS[i]=0;
+		//OFFSETS[i]=0; //<--removed this line, so that a failed tare does not undo previous tare
 	}
 
 	for (i=0; i<times; ++i) {
-		read(values);
+		readRaw(values);
 		for (j=0; j<COUNT; ++j) {
 			if (values[j]<minValues[j]) {
 				minValues[j]=values[j];
@@ -94,8 +96,12 @@ bool HX711MULTI::tare(byte times, uint16_t tolerance) {
 		for (i=0; i<COUNT; ++i) {
 			if (abs(maxValues[i]-minValues[i])>tolerance) {
 				//one of the cells fluctuated more than the allowed tolerance, reject tare attempt;
-				Serial.println("Rejecting tare");
-				Serial.println(abs(maxValues[i]-minValues[i]));
+				if (debugEnabled) {
+					Serial.print("Rejecting tare: (");
+					Serial.print(i);
+					Serial.print(") ");
+					Serial.println(abs(maxValues[i]-minValues[i]));
+				}
 				return false;
 			}
 		}
@@ -110,8 +116,21 @@ bool HX711MULTI::tare(byte times, uint16_t tolerance) {
 }
 
 //reads from all cahnnels and sets the values into the passed long array pointer (which must have at least 'count' cells allocated)
-//send NULL if you are only reading to toggle the line, and not to get values, such as in the case of setting gains.
+//if you are only reading to toggle the line, and not to get values (such as in the case of setting gains) you can pass NULL.
 void HX711MULTI::read(long *result) {
+
+    readRaw(result);
+
+    // Datasheet indicates the value is returned as a two's complement value, so 'stretch' the 24th bit to fit into 32 bits. 
+	if (NULL!=result) {
+		for (int j = 0; j < COUNT; ++j) {
+		    result[j] -= OFFSETS[j];   	
+		}
+	}
+}
+
+
+void HX711MULTI::readRaw(long *result) {
 	int i,j;
 	// wait for all the chips to become ready
 	while (!is_ready());
@@ -141,12 +160,15 @@ void HX711MULTI::read(long *result) {
 	    	} else {
 	    		result[j] &= 0x00FFFFFF; //required in lieu of re-setting the value to zero before shifting bits in.
 	    	}
-		    result[j] -= OFFSETS[j];   	
 	    } 
 
     }
 }
 
+void HX711MULTI::setDebugEnable(bool debugEnable) {
+	debugEnabled = debugEnable;
+}
+
 void HX711MULTI::power_down() {
 	digitalWrite(PD_SCK, LOW);
 	digitalWrite(PD_SCK, HIGH);

HX711-multi.h

@@ -15,6 +15,8 @@ class HX711MULTI
 		byte *DOUT;		// Serial Data Output Pin
 		byte GAIN;		// amplification factor
 
+		bool debugEnabled; //print debug messages?
+
 		long *OFFSETS;	// used for tare weight
 		float SCALE;	// used to return weight in grams, kg, ounces, whatever
 
@@ -43,6 +45,9 @@ class HX711MULTI
 		// waits for the chip to be ready and returns a reading
 		void read(long *result = NULL);
 
+		// same as read, but does not offset the values according to the tare
+		void HX711MULTI::readRaw(long *result = NULL);
+
 		// set the OFFSET value for tare weight
 		// times: how many times to read the tare value
 		// returns true iff the offsets have been reset for the scale during this call.
@@ -54,6 +59,8 @@ class HX711MULTI
 
 		// wakes up the chip after power down mode
 		void power_up();
+
+		void setDebugEnable(bool debugEnable = true);
 };
 
 #endif /* HX711_MULTI_h */