Using TUMPA for Serial-to-USB Communication

The current FTDI-based debugger I have on hand is the TIAO USB Multi Protocol Adapter (aka "TUMPA"). This little guy is pretty handy, and I have often used it for JTAG debugging.

Recently I found myself needing a USB-to-Serial device, so I decided to put my little TUMPA to work. I wired up the RX line and Ground on the DB9 connector so it was connected to the device, but all the data I received was garbage!

I beat my head against the wall for a while, until I noticed there was a separate TTL serial interface on the device!

It turns out that you need to use this TTL interface (which was not enabled by default on my device) for serial debugging.

To enable the TTL interface, look for the TTL/RS232 Jumper: 

And move all the connectors to the TTL-OUT side.

After that, wire your serial device to the TTL connector, and you'll be good to go!

TTL Pins

  1. Tx
  2. Rx
  3. RTS
  4. CTS
  5. DTR
  6. DSR
  7. DCD
  8. RI
  9. +3.3V
  10. +5V (USB Power)
  11. GND
  12. GND

NOTE: The power pins (9, 10, 11 and 12) are always connected, regardless of the jumper positions of Serial RS232/TTL level Selection Jumper.

Happy Hacking!

Further Reading