diff --git a/digital-inputs/firmware/can.h b/digital-inputs/firmware/can.h
index 38b3eb8..37c6d3c 100644
--- a/digital-inputs/firmware/can.h
+++ b/digital-inputs/firmware/can.h
@@ -12,6 +12,7 @@
 #define CAN_ISX(f) ((f).IDE)
 #endif
 
+// 0.02v precision
 #define getVoltageFrom8Bit(b) (5.0f * (b) / 255)
 
 void initCan();