Having developed and tested a project using an Arduino Uno, I would now like to upload it to an Arduino Pro Mini (5V, 328, 16MHz) for semi-permanent, long-term use, but I can't get any sign of life from the Pro Mini.

I'm using the latest Arduino IDE (v1.6.0 with Java 6, on Mac OS X Mavericks), and I've got a USB 2.0 to TTL UART 6PIN CP2102 Module Serial Converter to connect the Pro Mini to the Mac, and I've selected Tools —> Board —> Arduino Pro or Pro Mini (5V, 16MHz) w/ ATmega328.

The problem is that I don't see a suitable serial port in the list. When I plug in the Arduino Uno, "/dev/tty.usbmodem1421" immediately pops up in the Tools —> Serial Port menu, but I don't see anything similar with the Mini Pro.

The problem is probably in the connection between the USB/TTL converter and the Mini Pro, so my question is: which pins should connect to which?

USB/TTL converter face to face with Arduino Pro Mini

FWIW the USB/TTL converter was supplied with a 5-core (not 6-core) cable to connect its 6 pins.

So do I connect Tx—>Tx and Rx->Rx, or should they be crossed over? It's fairly clear that "5V" connects to "Vcc" and "GND" goes to "GND", but what about CTS and DTR?

Also FWIW, I have googled this, and I have read a number of other posts and answers on StackExchange, but the fact that I'm here writing my question means that I'm still stuck. Any and all constructive suggestions will be appreciated. Thanks!


2 Answers 2


You need to hook it up with the Arduino TX --> FTDI RX, and vise versa, so crossed over. If you take the FTDI and hook it up to the Ardiono pin to pin as you have it pictured it should work, provided the FTDI works.

No to your note about not having a serial port, you should have that as soon as you plug the FTDI into your computer, the Arduino is not necessary for this. First things first, check you drivers, and check your USB connection. You won't get anywhere until that Serial port is recognized on your computer.

  • Thanks for your help. I think I expected to see the serial port as soon as the FTDI was present, but wasn't sure. Now... drivers, you say? I'll go googling for those, unless someone has a helpful link...
    – Tim Morley
    Commented Mar 1, 2015 at 21:08
  • @TimMorley Mine always install automatically, but I'm on Windows. Who knows about you Mac guys :) I would think it would be pretty similar to the Arduino drivers (Maybe even compatible) but I don't use that particular FTDI device.
    – Butters
    Commented Mar 1, 2015 at 22:28
  • Yay! With drivers I got the COM port to show up in the Arduino IDE; and the advice in the comment from @kontur helped me to find the split second when I had to press the RESET button; and I now have my sketch uploaded to my Arduino Mini Pro. Thank you, @Butters!
    – Tim Morley
    Commented Mar 1, 2015 at 22:30
  • @TimMorley It looks like that FTDI is setup for the auto reset, so if you hook up all 6 pins, it should take care of the reset for you. When I have pins like that on one of my boards, I put them in the arduino, and with just a little force forward on the FTDI, enough contact is made to flash the Arduino.
    – Butters
    Commented Mar 1, 2015 at 22:34

If you still have any issues, try connecting the vcc and gnd to raw and gnd near the pins. Mine worked this way

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