PID rework - use watts

workspace/TS100/src/power.cpp

@@ -0,0 +1,48 @@
+/*
+ * power.cpp
+ *
+ *  Created on: 28 Oct, 2018
+ *     Authors: Ben V. Brown, David Hilton
+ */
+
+#include <power.hpp>
+#include <Settings.h>
+#include <hardware.h>
+
+history<uint16_t, 75> milliWattHistory = {{0}, 0, 0};
+
+const uint8_t tipResistance = 87;
+const uint8_t hz = 33;
+const uint8_t maxPWM = 100;
+
+int32_t tempToMilliWatts(int32_t rawTemp, uint16_t mass, uint8_t rawC) {
+	 // mass is in milliJ/*C, rawC is raw per degree C
+	int32_t milliJoules = mass * rawTemp / rawC;
+	return milliJoules * hz;
+}
+
+void setTipMilliWatts(int32_t mw) {
+	int32_t output = milliWattsToPWM(mw, systemSettings.voltageDiv / 10);
+	setTipPWM(output);
+	uint16_t actualMilliWatts = PWMToMilliWatts(output, systemSettings.voltageDiv / 10);
+
+	milliWattHistory.update(actualMilliWatts);
+}
+
+uint8_t milliWattsToPWM(int32_t milliWatts, uint8_t divisor) {
+	int32_t v = getInputVoltageX10(divisor); // 1000 = 10v
+	int32_t availableMilliWatts = v*v / tipResistance;
+	int32_t pwm = maxPWM * milliWatts / availableMilliWatts;
+
+	if (pwm > maxPWM) {
+		pwm = maxPWM;
+	} else if (pwm < 0) {
+		pwm = 0;
+	}
+	return pwm;
+}
+
+int32_t PWMToMilliWatts(uint8_t pwm, uint8_t divisor) {
+	int32_t v = getInputVoltageX10(divisor);
+	return pwm * (v*v / tipResistance) / maxPWM;
+}