Updated schematic to show use with a Rheostat instead of a potentiome…

…ter.

Fix bug in Teensy Emulate to allow replay of more than once curve.
Added concept of gain to record.

README.md

@@ -19,7 +19,7 @@ For more information on the concept, design, and evaluation of Ekho, checkout th
 - [Teensy ADC package installed](https://github.com/pedvide/ADC)
 - [GNU Scientific Library (GSL)](http://brewformulas.org/Gsl)
 - 2x [Teensy 3.1 Dev Boards](https://www.sparkfun.com/products/12646)
-- 1x [MCP413X/415X/423X/425X Digital Potentiometer](https://www.sparkfun.com/products/10613)
+- 1x [MCP413X/415X/423X/425X Digital Potentiometer](https://www.sparkfun.com/products/10613). Prefferably the 100k from Digikey: # MCP4152-104E/P-ND
 - Breadboard, headers, jumpers, iron will
 
 
@@ -40,7 +40,7 @@ Once the PCB is in hand, you can either:
 
 1. Flash the Teensy 3.1 with the `code/record/micro/EkhoRecord_t3.ino` image using the Arduino application.
 
-2. Connect the Teensy 3.1, the digital potentiometer (synthetic load) and the Analog-front end as shown above.
+2. Connect the Teensy 3.1, the digital potentiometer / rheostat (synthetic load) and the Analog-front end as shown above.
 
 3. Connect jumpers JP4 and the left side of JP1 for replay path.
 

code/emulate/micro/EkhoEmulate_t3.ino

@@ -3,70 +3,71 @@
 #include <RingBuffer.h>
 #include <RingBufferDMA.h>
 
-ADC *adc = new ADC(); // adc object
-byte response[6];
+ADC *adc = new ADC();
 uint16_t current_curve[65];
 const int statPin=21;
-int16_t interpolate_f(int16_t _adc_14_value, uint16_t _shift_bits) 
+int16_t current=0;
+int16_t voltage=0;
+unsigned char buf[512];
+uint16_t bcount = 0;
+uint16_t i = 0;
+
+uint16_t interpolate_f(uint16_t _adc_14_value, uint16_t _shift_bits) 
 {
-	int16_t left = _adc_14_value >> _shift_bits;
-	return  current_curve[left] -
+	uint16_t left = _adc_14_value >> _shift_bits;
+	return	current_curve[left] -
 				((
 					(uint32_t)(current_curve[left] - current_curve[left+1]) * 
 					(uint32_t)(_adc_14_value - (left << _shift_bits))
 				) >> _shift_bits);
 };
 
 void setup() {
-  Serial.begin(115200);
+	Serial.begin(115200);
 
-  pinMode(A3, INPUT);
-  pinMode(statPin, OUTPUT);
-
-  ////// ADC1 /////
-  adc->setAveraging(1, ADC_1); // set number of averages
-  adc->setResolution(12, ADC_1); // set bits of resolution
-  adc->setConversionSpeed(ADC_HIGH_SPEED, ADC_1); // change the conversion speed
-  adc->setSamplingSpeed(ADC_HIGH_SPEED, ADC_1); // change the sampling speed
+	pinMode(A3, INPUT);
+	pinMode(statPin, OUTPUT);
 
-  // 12-bit DAC
-  analogWriteResolution(12); 
-
-  // Let everything settle
-  delay(1000);
-}
+	////// ADC1 /////
+	adc->setAveraging(1, ADC_1); // set number of averages
+	adc->setResolution(12, ADC_1); // set bits of resolution
+	adc->setConversionSpeed(ADC_HIGH_SPEED, ADC_1); // change the conversion speed
+	adc->setSamplingSpeed(ADC_HIGH_SPEED, ADC_1); // change the sampling speed
 
-void printLine() {
-  Serial.print( response[0]);
-  Serial.print(",");
-  Serial.print( response[1]);
-  Serial.print(",");
-  Serial.print( response[2]);
-  Serial.print(",");  
-  Serial.println( response[3]);
+	// 12-bit DAC
+	analogWriteResolution(12); 
+
+	// Let everything settle
+	digitalWrite(statPin, LOW);
+	delay(2000);
 }
 
-uint16_t current=0;
-uint16_t voltage=0;
-unsigned char buf[512];
-uint16_t bcount = 0;
-uint16_t i = 0;
 void loop() {
-  digitalWrite(statPin, LOW);
-  while(Serial.available()) {
-    buf[bcount++] = Serial.read();
-    if(bcount > 130) {
-      for(i=0;i<130;i+=2) {
-        current_curve[i / 2] = (buf[i] << 8) + buf[i+1];
-      }
-      bcount = 0; 
-      break;
-    }
-  }
-  digitalWrite(statPin, HIGH);
-  voltage = adc->analogRead(A3, ADC_1);
-  analogWrite(A14, interpolate_f(voltage, 6));
-  //delayMicroseconds();
+	// Calculate output value (TODO: dont use float math, use a table)
+	voltage = adc->analogRead(A3, ADC_1);
+	//					  = voltage * (3.3 / 4096) * 4;
+	double actual_voltage = voltage * 0.00322265;
+	double actual_voltage_digital = actual_voltage / 0.0019178;
+	uint16_t avd = (uint16_t)actual_voltage_digital;
+
+	// Start reading in a new curve if necessary
+	while(Serial.available()) {
+		if(bcount == 0) {
+			digitalWrite(statPin, HIGH);
+		}
+		buf[bcount++] = Serial.read();
+		if(bcount > 129) {
+			digitalWrite(statPin, LOW);
+			for(i=0;i<130;i+=2) {
+				current_curve[i / 2] = (buf[i] << 8) + buf[i+1];
+			}
+			bcount = 0; 
+			break;
+		}
+	}
+
+	// Write to DAC
+	analogWrite(A14, interpolate_f(avd, 6));
 }