 #define DRAIN_MULT      (((33 + 10) / 10.0) * CALIBRATE_DRAIN)      // resistors 33k and 10k
 #define POWER5_MULT     (((10 + 10) / 10.0) * CALIBRATE_POWER5)     // resistors 10k and 10k
 #define POWER15_MULT    (((33 + 10) / 10.0) * CALIBRATE_POWER15)    // resistors 33k and 10k
+#define DR_CURRENT_MULT (100000.0 / 220 / 51)                       // resistors 51 and 220
 
 /*
  * Read a character from the serial port.

    } else {
        Serial.write("No power!");
    }

    Serial.write("\r\n  Power +5V: ");
    print_mv(power5_mv);

    // Configure pins.
    // D2 - gate output
    // A0 - gate input
    // A1 - drain voltage input with divisor 1:4.3
    // A2 - +5V input with divisor 1:2
    // A3 - +15V input with divisor 1:4.3
    // A4 - drain current input via ZXCT1009 current sense monitor
    //
    pinMode(gate_output_pin, OUTPUT);
    pinMode(A0, INPUT);
    pinMode(A1, INPUT);
    pinMode(A2, INPUT);
    pinMode(A3, INPUT);
    pinMode(A4, INPUT);

    // Configure timer 3 prescale factor as 1:1.
    // Set bits CS32,CS31,CS30 to 0b001.
