From 81888eb26b1ba44b89b0307e4a37907eb4a547b1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?King=20K=C3=A9vin?= <kingkevin@cuvoodoo.info>
Date: Wed, 28 Jan 2015 19:36:00 +0100
Subject: [PATCH] tune threshold and add weight interpretation

---
 firmware/main.c | 36 +++++++++++++++++++++---------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/firmware/main.c b/firmware/main.c
index e31842a..1c44871 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -29,15 +29,11 @@
 #include "main.h" // main definitions
 
 /* contants */
-// max measurement jitter for high and low value
-#define JITTER_HIGH 8
-#define JITTER_LOW 3
+// max measurement jitter for high and low value 8/3
+#define JITTER_HIGH 11
+#define JITTER_LOW 5
 // how many value have to be stable before showing output
 #define MEASUREMENT_STABLE 3
-// weight coefficient (timer 1 ticks/kg)
-// proportionally decreasing for high, increasing for low
-#define COEF_HIGH 41.78
-#define COEF_LOW 39.87
 
 /* variables */
 volatile uint8_t state_portD; // the state of port D
@@ -204,21 +200,31 @@ int main(void)
 				zero_high = measurement_high;
 				zero_low = measurement_low;
 #ifdef DEBUG
-				printf("zero values high/low: %u/%u\n", zero_high, zero_low);
+				printf("zero values high low: %u %u\n", zero_high, zero_low);
 #endif
-			} else { // prinf measurement weight
-				double weight_high = (int16_t)(zero_high-measurement_high)/COEF_HIGH;
-				double weight_low = (int16_t)(measurement_low-zero_low)/COEF_LOW;
-				double weight = (weight_high+weight_low)/2;
-				printf("%d kg\n", zero_high-measurement_high);
-				printf("%.2f kg\n", weight);
+				count_high = count_low = 0;
+			} else { // print measurement weight
+#ifdef DEBUG
+				printf("%u %u 0\n", zero_high, zero_low);
+				printf("%u %u t1\n", measurement_high, measurement_low);
+#endif
+	
+				// the low measurement are linear and more stable
+				// normally it should not have a origin, but the linear estimation shows one and it works better
+				const double orig_low = -1.92285;
+				const double coef_low = 0.0258119;
+				double weight_low = (int16_t)(measurement_low-zero_low)*coef_low+orig_low;
+				if (weight_low<orig_low*-1.5 && weight_low>orig_low*1.5) {
+					weight_low = 0;
+				}
+				printf("%.2f kg\n", weight_low);
 			}
 			count_high = count_low = 0;
 		}
 		/* display if scale switches off */
 		if (scale_old!=scale_on && !scale_on) {
 #ifdef DEBUG
-			printf(PSTR("scale stop\n"));
+			printf(PSTR("scale stop\n")); // actually measurement is finished and the on switch is released
 #endif
 			scale_old = scale_on; // save new state
 		}