Digital load control system providing power and communication via existing power wiring

A method to control an electric power device, comprising:

• supplying, by controller circuitry via electrical wiring, a periodic voltage to an electric power device, the controller circuitry couplable between a power source and the electric power device;
• transmitting, by the controller circuitry, a forward digital message to the electric power device by encoding digital information in timing edges of the periodic voltage;
• transmitting, by the controller circuitry, a short pattern that allows the electric power device to synchronize to a frequency of the periodic voltage prior to the electric power device transmitting a reverse digital message to the controller circuitry;
• performing, by the controller circuitry, error detection on the reverse digital message received from the electric power device;
• transmitting, by the controller circuitry, a retry pattern to the electric power device responsive to detection of an error in the reverse digital message;
• and
• receiving, by the controller circuitry, a retransmitted reverse digital message from the electric power device responsive to the receipt of the retry pattern by the electric power device.

A non-transitory, machine-readable, storage device that includes instructions that when executed by controller circuitry in an electric power device controller, cause the controller circuitry to:

• supply, via electrical wiring, a periodic voltage to an operatively coupled electric power device;
• transmit a forward digital message to the electric power device by encoding digital information in timing edges of the periodic voltage;
• transmit a short pattern that allows the electric power device to synchronize to a frequency of the periodic voltage prior to the electric power device transmitting a reverse digital message to the controller circuitry;
• perform error detection on the reverse digital message received from the electric power device;
• transmit a retry pattern to the electric power device responsive to detection of an error in the reverse digital message;
• and
• receive a retransmitted reverse digital message from the electric power device responsive to the receipt of the retry pattern by the electric power device.