7 files changed, 64 insertions, 2 deletions
diff --git a/spaghetti-monster/anduril/battcheck-mode.c b/spaghetti-monster/anduril/battcheck-mode.c
index c468332..3b4a144 100644
--- a/spaghetti-monster/anduril/battcheck-mode.c
+++ b/spaghetti-monster/anduril/battcheck-mode.c
@@ -35,6 +35,7 @@ uint8_t battcheck_state(Event event, uint16_t arg) {
         set_state(off_state, 0);
         return MISCHIEF_MANAGED;
     }
+
     #if defined(USE_BEACON_MODE)
     // 2 clicks: beacon mode
     else if (event == EV_2clicks) {
@@ -48,9 +49,37 @@ uint8_t battcheck_state(Event event, uint16_t arg) {
         return MISCHIEF_MANAGED;
     }
     #endif
+
+    #ifdef USE_VOLTAGE_CORRECTION
+    // 7 clicks: voltage config mode
+    else if (event == EV_7clicks) {
+        push_state(voltage_config_state, 0);
+        return MISCHIEF_MANAGED;
+    }
+    #endif
+
     return EVENT_NOT_HANDLED;
 }
 
+#ifdef USE_VOLTAGE_CORRECTION
+// the user can adjust the battery measurements... on a scale of 1 to 13
+// 1 = subtract 0.30V
+// 2 = subtract 0.25V
+// ...
+// 7 = no effect (add 0V)
+// 8 = add 0.05V
+// ...
+// 13 = add 0.30V
+void voltage_config_save() {
+    uint8_t foo = config_state_values[0];
+    if (foo) voltage_correction = config_state_values[0];
+}
+
+uint8_t voltage_config_state(Event event, uint16_t arg) {
+    return config_state_base(event, arg, 1, voltage_config_save);
+}
+#endif  // #ifdef USE_VOLTAGE_CORRECTION
+
 
 #endif
 
diff --git a/spaghetti-monster/anduril/battcheck-mode.h b/spaghetti-monster/anduril/battcheck-mode.h
index f57fa74..8ddf31d 100644
--- a/spaghetti-monster/anduril/battcheck-mode.h
+++ b/spaghetti-monster/anduril/battcheck-mode.h
@@ -22,5 +22,10 @@
 
 uint8_t battcheck_state(Event event, uint16_t arg);
 
+#ifdef USE_VOLTAGE_CORRECTION
+void voltage_config_save();
+uint8_t voltage_config_state(Event event, uint16_t arg);
+#endif
+
 
 #endif
diff --git a/spaghetti-monster/anduril/config-default.h b/spaghetti-monster/anduril/config-default.h
index c68e869..0957a29 100644
--- a/spaghetti-monster/anduril/config-default.h
+++ b/spaghetti-monster/anduril/config-default.h
@@ -86,6 +86,10 @@
 #define BATTCHECK_VpT
 //#define BATTCHECK_8bars  // FIXME: breaks build
 //#define BATTCHECK_4bars  // FIXME: breaks build
+// allow the user to calibrate the voltage readings?
+// (adjust in 0.05V increments from -0.30V to +0.30V)
+// (1 = -0.30V, 2 = -0.25V, ... 7 = 0V, ... 13 = +0.30V)
+#define USE_VOLTAGE_CORRECTION
 
 // enable beacon mode
 #define USE_BEACON_MODE
diff --git a/spaghetti-monster/anduril/load-save-config-fsm.h b/spaghetti-monster/anduril/load-save-config-fsm.h
index d9c5f4c..c7c4c8d 100644
--- a/spaghetti-monster/anduril/load-save-config-fsm.h
+++ b/spaghetti-monster/anduril/load-save-config-fsm.h
@@ -60,6 +60,9 @@ typedef enum {
     therm_ceil_e,
     therm_cal_offset_e,
     #endif
+    #ifdef USE_VOLTAGE_CORRECTION
+    voltage_correction_e,
+    #endif
     #ifdef USE_INDICATOR_LED
     indicator_led_mode_e,
     #endif
diff --git a/spaghetti-monster/anduril/load-save-config.c b/spaghetti-monster/anduril/load-save-config.c
index 7268dc9..8360ee4 100644
--- a/spaghetti-monster/anduril/load-save-config.c
+++ b/spaghetti-monster/anduril/load-save-config.c
@@ -60,6 +60,9 @@ void load_config() {
         therm_ceil = eeprom[therm_ceil_e];
         therm_cal_offset = eeprom[therm_cal_offset_e];
         #endif
+        #ifdef USE_VOLTAGE_CORRECTION
+        voltage_correction = eeprom[voltage_correction_e];
+        #endif
         #ifdef USE_INDICATOR_LED
         indicator_led_mode = eeprom[indicator_led_mode_e];
         #endif
@@ -114,6 +117,9 @@ void save_config() {
     eeprom[therm_ceil_e] = therm_ceil;
     eeprom[therm_cal_offset_e] = therm_cal_offset;
     #endif
+    #ifdef USE_VOLTAGE_CORRECTION
+    eeprom[voltage_correction_e] = voltage_correction;
+    #endif
     #ifdef USE_INDICATOR_LED
     eeprom[indicator_led_mode_e] = indicator_led_mode;
     #endif
diff --git a/spaghetti-monster/fsm-adc.c b/spaghetti-monster/fsm-adc.c
index 45a4297..96c4af3 100644
--- a/spaghetti-monster/fsm-adc.c
+++ b/spaghetti-monster/fsm-adc.c
@@ -114,7 +114,12 @@ static inline uint8_t calc_voltage_divider(uint16_t value) {
     // use 9.7 fixed-point to get sufficient precision
     uint16_t adc_per_volt = ((ADC_44<<5) - (ADC_22<<5)) / (44-22);
     // shift incoming value into a matching position
-    uint8_t result = ((value>>1) / adc_per_volt) + VOLTAGE_FUDGE_FACTOR;
+    uint8_t result = ((value>>1) / adc_per_volt)
+                     + VOLTAGE_FUDGE_FACTOR
+                     #ifdef USE_VOLTAGE_CORRECTION
+                     + voltage_correction - 7
+                     #endif
+                     ;
     return result;
 }
 #endif
@@ -262,7 +267,12 @@ static inline void ADC_voltage_handler() {
     // calculate actual voltage: volts * 10
     // ADC = 1.1 * 1024 / volts
     // volts = 1.1 * 1024 / ADC
-    voltage = ((uint16_t)(2*1.1*1024*10)/(measurement>>6) + VOLTAGE_FUDGE_FACTOR) >> 1;
+    voltage = ((uint16_t)(2*1.1*1024*10)/(measurement>>6)
+               + VOLTAGE_FUDGE_FACTOR
+               #ifdef USE_VOLTAGE_CORRECTION
+               + voltage_correction - 7
+               #endif
+               ) >> 1;
     #endif
 
     // if low, callback EV_voltage_low / EV_voltage_critical
diff --git a/spaghetti-monster/fsm-adc.h b/spaghetti-monster/fsm-adc.h
index cc33264..56583bb 100644
--- a/spaghetti-monster/fsm-adc.h
+++ b/spaghetti-monster/fsm-adc.h
@@ -52,6 +52,11 @@ void adc_deferred();  // do the actual ADC-related calculations
 
 static inline void ADC_voltage_handler();
 uint8_t voltage = 0;
+#ifdef USE_VOLTAGE_CORRECTION
+// same 0.05V units as fudge factor,
+// but 7 is neutral, and the expected range is from 1 to 13
+uint8_t voltage_correction = 7;
+#endif
 #ifdef USE_LVP
 void low_voltage();
 #endif