TT078: Greiner AC Line Synchronizer

Creates TTL pulses that are phase-locked to the AC line, and phase adjustable in 5 usec increments.

This version has two outputs: a continuous output which pulses high (5V) for 1 msec after a programmable delay after the start of each AC cycle,

and a triggered output which waits for a rising edge from the trigger input, then waits for the start of the next AC cycle, then generates a high pulse after a programmable delay.

The base is the TipTop1590BBRP, minimally stuffed:

Basically just the RP2040 with its support hardware and a 3.3V regulator.  Schematic:

Here's the AC input board:

It takes 12VAC from a wall wart, and creates 5V for the microcontroller, and a logic-level AC input signal.

Trigger input board is a standard ToprIsoDin2:

Since we only have one trigger input, only U2 and assoc components installed. Used HCPL-0211 for isolator.

Output is a standard ToprDout2:

Code is written in Arduino, taking advantage of the dual processors of the RP2040.  Processor 1 deals with the user interface over the USB serial port, and processor 2 runs a 200KHz state machine, which it phase-locks to the AC input, and generates the output pulses.

The user can adjust the phase timing over the USB virtual com port by sending:

D <arg> ;

where <arg> is the delay in 5-usec increments from the beginning of the AC cycle.  Acceptable range for arg is 0 to 3100.  Positive integers only.

The processor will echo the command as it is sent.  If it accepts the command, it will replace the ";" with a "!".  If not, it will replace it with a "?".

To store the new delay in non-volatile memory, send:

S;

The processor will respond with  "EEPROM Write Completed" or "EEPROM Write Failed".

Here's the code: