ambient.c: detect drop of ambient light

Measure also longer-term running average of ambient light values,
and log instead of minima and maxima of adc readings the diffrence
between this longer-term average and normal avereage (ambient_val).
This is so that we would be able to switch the front light on when
entering a darkish area from the bright sun.

diff --git a/firmware/ambient.c b/firmware/ambient.c
index 4f257aea87df0519e7d4105038e78f977dd27a8c..b8397532026fed989d06ff6454974be46e043850 100644 (file)
--- a/firmware/ambient.c
+++ b/firmware/ambient.c
@@ -4,9 +4,9 @@
 #include "lights.h"
 
 #define AMBIENT_VAL_SHIFT 2
-static uint16_t ambient_val;
+static uint16_t ambient_val, ambient_val16;
 volatile unsigned char ambient_zone;
-static unsigned char ambient_min, ambient_max;
+static unsigned char ambient_min, ambient_max, ambient_16drop;
 
 /* logging */
 #define AMBIENT_LOG_SIZE 128
@@ -34,9 +34,11 @@ static ambient_zone_t ambient_zones[] = {
 void init_ambient()
 {
        ambient_val = 0;
+       ambient_val16 = 0;
        ambient_max = 0;
        ambient_min = 0xFF;
        ambient_zone = 1;
+       ambient_16drop = 0;
 
        ambient_log_offset = eeprom_read_byte(&ambient_log_offset_stored);
 
@@ -62,10 +64,12 @@ void ambient_log_min_max()
                return;
 
        eeprom_write_byte(&ambient_log[ambient_log_offset++], ambient_min);
-       eeprom_write_byte(&ambient_log[ambient_log_offset++], ambient_max);
+       // eeprom_write_byte(&ambient_log[ambient_log_offset++], ambient_max);
+       eeprom_write_byte(&ambient_log[ambient_log_offset++], ambient_16drop);
 
        ambient_min = 0xFF;
        ambient_max = 0;
+       ambient_16drop = 0;
 }
 
 void ambient_zone_changed()
@@ -85,7 +89,7 @@ void ambient_zone_changed()
 void ambient_adc(uint16_t adcval)
 {
        unsigned char old_zone = ambient_zone;
-       unsigned char byte_val;
+       unsigned char byte_val, byte_val16;
 
        ambient_val += adcval - (ambient_val
                >> (AMBIENT_VAL_SHIFT - AMBIENT_ADC_SHIFT));
@@ -96,7 +100,16 @@ void ambient_adc(uint16_t adcval)
        while (ambient_zones[ambient_zone].hi < ambient_val)
                ambient_zone++;
 
-       byte_val = adcval >> 2;
+       byte_val = ambient_val >> (2 + AMBIENT_VAL_SHIFT - AMBIENT_ADC_SHIFT);
+
+       ambient_val16 += byte_val - (ambient_val16 >> 4);
+       byte_val16 = ambient_val16 >> 4;
+
+       if (byte_val16 > byte_val) {
+               byte_val16 -= byte_val;
+               if (byte_val16 > ambient_16drop)
+                       ambient_16drop = byte_val16;
+       }
 
        if (ambient_min > byte_val)
                ambient_min = byte_val;