3 files changed, 31 insertions, 6 deletions
diff --git a/spaghetti-monster/fsm-adc.c b/spaghetti-monster/fsm-adc.c
index 0b79767..a196b7b 100644
--- a/spaghetti-monster/fsm-adc.c
+++ b/spaghetti-monster/fsm-adc.c
@@ -12,6 +12,8 @@
 #define ADMUX_THERM ADMUX_THERM_EXTERNAL_SENSOR
 #endif
 
+#include <avr/sleep.h>
+
 
 static inline void set_admux_therm() {
     #if (ATTINY == 1634)
@@ -70,6 +72,29 @@ inline void set_admux_voltage() {
     ADC_start_measurement();
 }
 
+
+#ifdef TICK_DURING_STANDBY
+inline void adc_sleep_mode() {
+    // needs a special sleep mode to get accurate measurements quickly 
+    // ... full power-down ends up using more power overall, and causes 
+    // some weird issues when the MCU doesn't stay awake enough cycles 
+    // to complete a reading
+    #ifdef SLEEP_MODE_ADC
+        // attiny1634
+        set_sleep_mode(SLEEP_MODE_ADC);
+    #elif defined(AVRXMEGA3)  // ATTINY816, 817, etc
+        // set the RUNSTDBY bit so ADC will run in standby mode
+        ADC0.CTRLA |= 1;
+        // set a INITDLY value because the AVR manual says so
+        // (section 30.3.5)
+        ADC0.CTRLD |= (1 << 5);
+        set_sleep_mode(SLEEP_MODE_STANDBY);
+    #else
+        #error No ADC sleep mode defined for this hardware.
+    #endif
+}
+#endif
+
 inline void ADC_start_measurement() {
     #if (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85) || (ATTINY == 841) || (ATTINY == 1634)
         ADCSRA |= (1 << ADSC) | (1 << ADIE);
diff --git a/spaghetti-monster/fsm-adc.h b/spaghetti-monster/fsm-adc.h
index b25b650..1bb67ed 100644
--- a/spaghetti-monster/fsm-adc.h
+++ b/spaghetti-monster/fsm-adc.h
@@ -106,3 +106,7 @@ inline void ADC_on();
 inline void ADC_off();
 inline void ADC_start_measurement();
 
+#ifdef TICK_DURING_STANDBY
+inline void adc_sleep_mode();
+#endif
+
diff --git a/spaghetti-monster/fsm-standby.c b/spaghetti-monster/fsm-standby.c
index 2ce3a24..5def07c 100644
--- a/spaghetti-monster/fsm-standby.c
+++ b/spaghetti-monster/fsm-standby.c
@@ -41,12 +41,8 @@ void sleep_until_eswitch_pressed()
 
         // configure sleep mode
         #ifdef TICK_DURING_STANDBY
-            // needs a special sleep mode to get accurate measurements 
-            // quickly ... full power-down ends up using more power 
-            // overall, and causes some weird issues when the MCU 
-            // doesn't stay awake enough cycles to complete a reading
-            if (adc_active_now)
-                set_sleep_mode(SLEEP_MODE_ADC);
+            // needs a special sleep mode during measurements
+            if (adc_active_now) adc_sleep_mode();
             else
         #endif
         set_sleep_mode(SLEEP_MODE_PWR_DOWN);