Add some conversions from celsius to adc valuesHEADmaster

Luckily, this ATMega is grossly oversized, so we can
just throw in floating point arithmetic.

1 files changed, 41 insertions, 6 deletions

diff --git a/controller.c b/controller.c
index bde2cac..6dee4da 100644
--- a/controller.c
+++ b/controller.c
@@ -1,9 +1,13 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
+#include <math.h>
+#include <stdio.h>
+#include <string.h>
 
 #include "controller.h"
 
 #include "bridge.h"
+#include "serial.h"
 
 static void adc_init(void)
 {
@@ -40,20 +44,43 @@ void controller_init(void)
 	timer_init();
 }
 
-int controller_set(long target)
+static long celsius_to_adc(double target_temp)
 {
-	if (target < 50 || target > 974)
+	long rv;
+
+	rv = 1203.59290 * exp(-0.0686201496 * target_temp) + 413.59437;
+	if (rv > 1017)
+		return 1017;
+	if (rv < 450)
+		return 450;
+	return rv;
+}
+
+static double adc_to_celsius(long adc)
+{
+	double rv;
+
+	rv = adc - 413.59437;
+	rv /= 1203.59290;
+	rv = log(rv);
+	rv /= -0.0686201496;
+	return rv;
+}
+
+int controller_set(double target)
+{
+	if (target < 8.0 || target > 42.0)
 		return 1;
 
-	controller_target_temp = target;
+	controller_target_temp = celsius_to_adc(target);
 	controller_num_iterations = 1;
 	controller_active = 1;
 	return 0;
 }
 
-long controller_get(void)
+double controller_get(void)
 {
-	return controller_measured_temp;
+	return adc_to_celsius(controller_measured_temp);
 }
 
 void controller_off(void)
@@ -82,8 +109,16 @@ ISR(ADC_vect)
 		return;
 
 	controller_num_iterations--;
-	if (controller_num_iterations)
+	if (controller_num_iterations) {
+#if 0
+		char buffer[128];
+		snprintf(buffer, sizeof(buffer), "DEBUG adc==%ld adc_target=%ld\r\n",
+				(long int)controller_measured_temp,
+				controller_target_temp);
+		serial_send(buffer, strlen(buffer), 0);
+#endif
 		return;
+	}
 
 	controller_num_iterations = 60;