diff --git a/display/software/powerboard/src/adc.c b/display/software/powerboard/src/adc.c
index 42e7b4c..8ad8969 100644
--- a/display/software/powerboard/src/adc.c
+++ b/display/software/powerboard/src/adc.c
@@ -30,12 +30,13 @@ uint16_t adc_read_single(uint8_t channel) {
   return ADCW;
 }
  
-uint16_t adc_read_avg(uint8_t channel, uint8_t nsamples) {
-  uint32_t sum = 0;
+uint16_t adc_read_avg(const uint8_t channel, const uint8_t nsamples) {
+  uint16_t sum = 0;
+  uint8_t count = nsamples % 60;
  
-  for (uint8_t i=0; i<nsamples;++i ) {
+  for (uint8_t i=0; i<count;++i ) {
     sum += adc_read_single(channel);
   }
  
-  return (uint16_t)(sum / nsamples);
+  return (sum / count);
 }
diff --git a/display/software/powerboard/src/adc.h b/display/software/powerboard/src/adc.h
index 9073638..975f8be 100644
--- a/display/software/powerboard/src/adc.h
+++ b/display/software/powerboard/src/adc.h
@@ -1,8 +1,8 @@
 #ifndef _adc_h
   #define _adc_h
 
-	void adc_init(void);
-	uint16_t adc_read_single(uint8_t);
-	uint16_t adc_read_avg(uint8_t, uint8_t);
+	extern void adc_init(void);
+    extern uint16_t adc_read_single(uint8_t);
+	extern uint16_t adc_read_avg(uint8_t, uint8_t);
 
 #endif