R45 1K5
R50 15K
R51,R53 0R00 (zero-ohm link)
-R55 1R0 (can safely measure currents from ~8 mA up, for smaller currents use higher value)
+R55 3R0 (can safely measure currents from ~1 mA up, for higher currents use lower value)
U1 ATtiny45-20SU
U2 MCP1703T-5V