     // Configure pins.
     // D2 - gate output
     // A0 - gate input
-    // A1 - drain input with divisor 1:4.3
+    // 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.

 * Measure drain voltage.
 * Repeat until the value is stable for 3 attempts.
 */
void measure_drain()
{
    delay(1);
    drain_input = analogRead(A1);

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

    Serial.write("\r\nDrain current: ");
    print_uamp(drain_uamp);
    Serial.write(" (");
    Serial.print(drain_current_input);
    Serial.write(")");

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