Buying a reliable USB to serial adaptor?

I'm looking for a cheap UK source for a USB to serial adaptor, as a neat way of programming my new MEGA328 chips, as shown in this video tutorial:

But, as a novice, I'm confused by reading in several places, inlcuding this wiki page

that there are issues over validity. Some users of USB to serial adaptors report that they don't work, with messages like ""NON GENUINE DEVICE FOUND!"

Terry, East Grinstead, UK


I think the most important thing about an FTDI adapter is getting one with the pins arranged in the right order to just plug into and work with a Pro Mini. It is a standard arrangement for Arduino, and also works with boards such as Lilypad. The one spycatcher2k mentions has that arrangement. When you build your own boards, if you follow the same pinout, you can just plug it in.

In my opinion, the female headers belong on the FTDI adapter, and the male belongs on the Pro Mini. But I will admit that Youtube video shows plugging the FTDI adapter into the breadboard and it's convenient. Perhaps keep one of each on hand, or get some male to male header pins like these so you can use a female pin adapter with a breadboard.


I like this FTDI adapter made by TinySine, very similar to the one spycatcher2k mentions except already has a header strip soldered onto it. I like to add a label.


For programming, you can consider the Pololu USB AVR Programmer v2 (or V2.1).

The added bonus is that it’s a programmer as well and can be used to e.g. burn the bootloader or upload code via ICSP; it further supports both 3.3V and 5V devices. It possibly will not fit your criteria of cheap.

That looks like a pretty cool device to have and not bad price. Have you plugged that into a Pro Mini where pin A on it would be shorted to ground? I suppose it should handle that OK, I guess it depends on whether they put a resistor in that line.

I can't remember how I connected it to the pro-mini. But I think I wired it.

I mostly use it on Nanos to load application via ICSP..

Some users of USB to serial adaptors report that they don’t work, with messages like "“NON GENUINE DEVICE FOUND!”

There was a Hackaday article about this and I expected it to be FTDIgate round two but in the years since I have never once seen a report of this, and I know there are plenty of people on this forum using counterfeit FTDI FT232 chips. I myself use exclusively counterfeit FT232 chips (I bought a few of the cheap FT232 modules on eBay years before FTDIgate) and have never had any problems of this sort. Perhaps there was a single driver release with the message that was quickly replaced with one without the message. That is what happened with the original “FTDIgate” bricking driver.

If you buy a ridiculously cheap product with an FTDI FT232, it will almost certainly be fake. FT232 modules are sold by the Chinese on eBay for $0.75 with free shipping. It should come as no surprise when something at that price doesn’t turn out to be exactly what it was advertised as.

If you want cheap with less risk of counterfeit, you might look for products that use the CH340 instead. The genuine CH340 are already so cheap that I don’t think there is much motivation to counterfeit.

I very much second dmjlambert’s advice about getting the modules/cables with the standardized “FTDI header” pinout:

  • DTR or RTS
  • RX
  • TX
  • VCC
  • CTS
  • GND

Unfortunately, a lot of the CH340 modules do not use this pinout, and often don’t even break out the DTR or RTS signal you need to be able to upload without having to manually press the reset button at just the right time. You can find modules with the correct pinout, and they are usually only a few cents more expensive so it’s well worth shopping around to make sure you don’t get one of the inferior modules.

Search Ebay for ch340g 6pin, and look for the black cirguit boards with the voltage switch. They have the correct pinout, and work very well - that's what I use. The green ones with the micro usb connector are also good, they also have voltage switch.

The red ones with the correct pinout are not, however - you cant set them for 3.3v - it looks like you could, since they have a solder bridge you're supposed to be able to connect... but if you try it, they dont work afterwards.