What's Pmod232?
Some of
recent Digilent's
FPGA boards, such
as Nexys-3
and Atlys
have on-board FT232 (USB-UART bridge) but they don't have
classic D-sub 9 pin connector.
Although the on-board USB-UART bridge is useful, sometimes we still need D-sub 9 pin serial connector. Fortunately Digilent FPGA cards have 12-pin "Pmod" connectors, which provide 3.3V power and 8 signals.
Pmod232 is a simple, Maxim's MAX3232 based RS-232 transceiver for Digilent Pmod connector.
Schematic
The schematic PDF file is here.
Components
- Header: 6 pin 2.54mm headers x 1
- D-sub: 9 pin female x 1
- Maxim MAX232CPE (Plastic 16pin DIP)
- Resistors: 1k x 2
- Capacitors: 0.1uF x 5 (any type, my one has ceramic capacitors)
- 2.54mm universal circuit board x 1
Note
My Pmod232 board in above picture has a 8 pin header. The pins are: NC, NC, Rx1, Tx1, Rx2, Tx2, GND and Vcc3.3, from left to right. Be careful about the header location on the board, to plug it directly to the FPGA board.
Rx1 and Tx1 on the header can drive (and be driven) by UART module on the FPGA. MAX3232 has 2 RS-232C transceivers, so we can use Rx2 and Tx2 by adding one more 9 pin D-sub connector.
The board works fine with my Nexys-3 board at 9600bps. Also, the board has several additional capacitors for Vcc decoupling.
Contact
- Any questions are welcome: send an e-mail to osana at eee.u-ryukyu.ac.jp