I am trying to use fpga de2115 and (ftdi ft232rl usb to serial) to communicate with pc. Can the tx/rx pins from the adapter be connected directly to the fpga gpio pins? The board has rs232 port , but i don't have the rs232 cable and also want to avoid this. So can i assign uart hdl assigned pins to fpga gpio and connect them to the adapter tx/rx pins?

thank you.

  • 3
    \$\begingroup\$ "de2115" is not an FPGA. Is it possible you're referring to the Altera DE2-115 Development and Education Board from Terasic? The actual FPGA on that board is a Cyclone EP4CE115. \$\endgroup\$
    – Dave Tweed
    Sep 29, 2019 at 23:22
  • 2
    \$\begingroup\$ The main issue would be if the IO voltage is sufficiently compatible. IIRC some cyclone parts could not tolerate nominally 3v3 sigmals if they had any ringing on top. \$\endgroup\$ Sep 29, 2019 at 23:43
  • \$\begingroup\$ amazon.com/dp/B0753HBT12 \$\endgroup\$
    – vicatcu
    Sep 29, 2019 at 23:58
  • \$\begingroup\$ You can use it directly with General Purpose IOs, if it's a standard 3.3V cable. \$\endgroup\$
    – Mitu Raj
    Sep 30, 2019 at 4:28
  • \$\begingroup\$ yes ...the board is altera de2-115, default volt is 3.3V on gpios of the board.....the (usb to serial) adapter is also switchable to 3.3v....... \$\endgroup\$
    – NN Nnation
    Sep 30, 2019 at 19:33

1 Answer 1


Make sure you have set the correct voltage level for pins in the GPIO expansion header to 3.3V

Refer to page 46

These pins have tolerance upto 3.7 V, hence you should be able to use your USB-TTL 3.3V cable's rx and tx directly.

Don't forget the ground connection as well.

  • \$\begingroup\$ thanks for your answer.....so i need to make at least 3-connections ....({adapter-tx} to {hdl-assigned-gpio-rx}) , ({adapter-rx} to {hdl-assigned-gpio- tx}) and ({adapter-gnd} to {fpga-labeled/dedicated-gpio-gnd})...?? \$\endgroup\$
    – NN Nnation
    Oct 2, 2019 at 8:33
  • \$\begingroup\$ That's right................. \$\endgroup\$
    – Mitu Raj
    Oct 2, 2019 at 8:34

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