Fg3pico is 3 channels frequency generator based on Raspberry Pi Pico 2, it should be compatible with any RP3250 board (but not tested). It can be used for various purposes, for example, it can drive 3 phase motors or can be used for 3 phase AC generation

Features

• Frequency outputs are digital, the pins used for output are GP2, GP3, GP4
• Generator is driven by UART commads. UART pins used are default GP0 and GP1
• UART over USB can be used. It automatically switches over to USB when USB host is connected
• Each frequency has startup delay, 'on' period and 'off' period adjustable parameters. Also generation can be turned off independently for each channel
• Frequency parameters can be stored in on-board flash memory and loaded from flash.
• At board power-up it checks if there are frequencies stored. They are loaded from flash memory and generation starts automatically, no need to connect and setup by UART

Capabilities

Thanks to rp2350 pio features this board has excellent capabilities

• Min timing units 3
• Max timing units 4294967295
• CPU ticks per one time unit 1
• CPU ticks per one second 200000000

So this device has 5ns resolution per one unit. Max frequency it is able to generate is 33 MHz

UART commands

Each command contains additional CRC bytes at the end. The checksum algorithm used is CRC16/MODBUS.
The UART speed is 19200 bps. All values use big endian byte ordering (highest byte comes first)

• Command 01 - SET FREQUENCIES
  if ON period equals to 0 then frequency is muted (off)
  Command contains 39 bytes. F1, F2, F3 - three frequencies

  Command	0x01
  DELAY for F1	32 bit value
  ON period for F1	32 bit value
  OFF period for F1	32 bit value
  DELAY for F2	32 bit value
  ON period for F2	32 bit value
  OFF period for F2	32 bit value
  DELAY for F3	32 bit value
  ON period for F3	32 bit value
  OFF period for F3	32 bit value
  CRC16 Checksum	16 bits

• Command 02 - STORE TO FLASH
  Stores current frequencies in flash memory

  0x02	0x81	0x3E

• Command 03 - LOAD FROM FLASH
  Loads frequencies from the flash, this is done also at the reset (startup)

  0x03	0x41	0xFF

• Command 04 - CHECK CAPABILITIES
  Request device capabilities (timing range, ticks per one unit, cpu ticks per second)

  0x04	0x83	0xBE

• Possible device responses:

  OK, COMMAND EXECUTED

  0x00	CRC checksum 16 bits

  BAD COMMAND (CRC ERROR)

  0x01	CRC checksum 16 bits

  BAD DATA IN FLASH (CRC ERROR)

  0x02	CRC checksum 16 bits

  CAPABILITIES (Response to command 04)

  Command	0x04
  Min units 3	0x00	0x00	0x00	0x03
  Max units 4294967295	0xff	0xff	0xff	0xff
  Ticks per one unit 1	0x00	0x00	0x00	0x01
  CPU ticks per one second 200000000	0x0b	0xeb	0xc2	0x00
  CRC 16 bits	CRC high byte	CRC low byte