Serial port modem with a FPGA

"YAM" is the name of a modem developed by Nico Palermo IV3NWV using a XC5202 FPGA from Xilinx. This modem is plugs into the serial port of any PC and is capable of

  • 1200 Baud AFSK
  • 2400 Baud Manchester FSK
  • 9600 Baud FSK (G3RUH)
    with a different Quarz you can also get 19200, 28800 and 57600 Baud.
For a complete description of the original modem look at
Some time in 1998 I created a slightly different version of the YAM modem, the YAMSMD
modem. It uses SMD components and measures only 52x32mm!

Miniature version of this modem using SMD parts:

Top side of the modem (the FPGA is below the quarz!)

Bottom side of the modem

Most of the parts are 0603 size resistors and capacitors, the FPGA has a VQ64 package. The modem produces standard RS232 signals by using a Motorola MC145405 interface chip.

Schematic of the modem
Top side place plan
Bottom side place plan
Top side layout
Bottom side layout
German description as published in Adacom-Magazin 12(1998)

Flexnet driver available here!

Note: You do not need a 16550 UART to use this modem. The UART FIFO is neither recognized nor used by any driver.

DF2FQ published an excellent 70cm data transceiver for 9600 baud FSK using two point modulation. Look at the picture: 
T7F transceiver

Last change: 27.June 1999