some changes, hunting for bugs

firmware/Makefile

@@ -1,4 +1,5 @@
 CFLAGS += -Wall -Os  -I. -mmcu=attiny24 -std=c99
+#CFLAGS += -save-temps
 DEFINES += -DF_CPU=1e6
 
 OBJECTS = cup.o

firmware/cup.c

@@ -16,8 +16,8 @@
 const uint16_t LED_GREEN_TEMP = 300;
 const uint16_t LED_RED_TEMP = 1200;
 
-const uint16_t TARGET_TEMP_MIN = 300;
-const uint16_t TARGET_TEMP_MAX = 1520;
+#define TARGET_TEMP_MIN 300
+#define TARGET_TEMP_MAX 1520
 
 uint8_t setting_timeout = 0;
 
@@ -80,7 +80,7 @@ ISR(PCINT0_vect)
 	int8_t change = state_change[((input_state & 3) << 2) | (new_state & 3)];
 	if(change)
 	{
-		target += change << 4;
+		target += change * 10; // 1 celsius per step
 		if(target < TARGET_TEMP_MIN) {target = TARGET_TEMP_MIN;}
 		else if(target > TARGET_TEMP_MAX) {target = TARGET_TEMP_MAX;}
 		setting_timeout = TIMEOUT;
@@ -128,14 +128,21 @@ inline uint16_t linearize_temp(uint16_t temp_in)
 		59911, 1300,
 		62902, 1400,
 		65474, 1500, // 150 celsius
-		65535, 1520, // made-up, not from datasheet
+		65535, TARGET_TEMP_MAX // 152 celsius, made-up, not from datasheet
 	};
 	uint8_t i=2;
 	for (; i < (sizeof(coeffs)>>1)-2; i+=2)
 	{
 		if ( temp_in < pgm_read_word(&coeffs[i]) )
 		{
-			temp_out = (uint16_t) ( pgm_read_word(&coeffs[i-1]) + (uint32_t) ( (uint32_t) (temp_in - pgm_read_word(&coeffs[i-2])) * (pgm_read_word(&coeffs[i+1])-pgm_read_word(&coeffs[i-1])) ) / (pgm_read_word(&coeffs[i])-pgm_read_word(&coeffs[i-2])));
+			temp_out = (uint16_t) (
+                    pgm_read_word(&coeffs[i-1]) + 
+                    (uint32_t) (
+                        (uint32_t) (temp_in - pgm_read_word(&coeffs[i-2])) *
+                        (pgm_read_word(&coeffs[i+1])-pgm_read_word(&coeffs[i-1]))
+                    ) /
+                    (pgm_read_word(&coeffs[i])-pgm_read_word(&coeffs[i-2])));
+
 			break;
 		}
 	}
@@ -160,14 +167,16 @@ inline void led_init(void)
 
 inline void led_set(uint16_t value)
 {
-	if (LED_GREEN_TEMP < value && value < LED_RED_TEMP) {
-		value = ((uint32_t) (value-LED_GREEN_TEMP) * 255)/(LED_RED_TEMP-LED_GREEN_TEMP);
-	} else if (value < LED_GREEN_TEMP) {
-		value = 0;
+    uint8_t pwmval;
+	if (LED_GREEN_TEMP <= value && value < LED_RED_TEMP) {
+		pwmval = ((uint32_t) (value-LED_GREEN_TEMP) * 255)/(LED_RED_TEMP-LED_GREEN_TEMP);
+	} else if (value <= LED_GREEN_TEMP) {
+		pwmval = 0;
 	} else {
-		value = 255;
+		pwmval = 255;
 	}
-	OCR0A = OCR0B = (uint8_t)value;
+	OCR0A = pwmval;
+	OCR0B = pwmval;
 }
 
 inline void led_off(void)