DIY Programmer Cable

If there are any errors, let me know

As we all know, programmer cables are no longer being made for purchase. The good news is that you can make your own programmer cable for only a few dollars in parts and a few minutes of your time!

!!!DISCLAIMER!!! Undertake the project at your own risk. I am not responsible for fried OSMs in the event something goes wrong. If you break it you get to keep both pieces! Additionally, I do not have an OSM2 to test this with yet, this tutorial has been made after reviewing the OSM2 pinout diagram. Again, undertake the project at your own risk!

    To make your own programmer cable, you will need the following:
  • FTDI Breakout Board (USB to Serial), can be found for a couple bucks online
  • Micro USB Cable, usaully can be obtained for free lying around the house
  • Pliers/Wire Stripper, any tool, even scissors can be used to cut and strip wire
  • Female Jumper Wire, sometimes included when you buy an FTDI Breakout Board but also can be bought for pennies
  • Electrical Tape, used to insulate connections

    Recommended Items (Not necessary to make a working cable but looks nice):
  • Heatshrink tubing, makes the end result neater and more secure
  • Soldering Iron, offers perfect electrical connection, in a pinch you can twist the wires together and tape them
  • Label Maker, used to label each cable


USB Cable on the left and FTDI Programmer on the right with jumper wires attached

The first step is to break out the wire snips and cut the USB cable in half. Strip away the top insulation to reveal the braided shielding.

Peel back the shielding to expose a foil like wrapper. This foil wrapper can also be pulled back and torn off. Twist the shielding into a single wire and strip the remaining 4 wires as pictured below. The string is for structural purposes and can be ignored.

Now it is time to find out which wire goes where. Here is a handy chart which shows you which wire from the USB cable correlates to which pin on the FTDI Breakout:

CTS does not need to be connected.

It is now time to solder these for good. If you have heat shrink, now is a good time to slip a bit of heat shrink on each wire and a large one onto the USB cable. If you do not have a soldering iron, simply twist the wire pairs together and tape the connection securely. Be sure to eliminate the chances of shorts, which is why it is good practice to either tape or heat shrink wrap each individual wire connection.

Completed soldering with heat shrink ready to go

At this point the physical work is more or less complete and you should have a fully assembled programming cable:

I took the opportunity to label each individual jumper wire because I use my FTDI programmer for other purposes.

After this, drivers should be installed as normal and you can begin using the programmer cable!

Re: DIY Programmer Cable

Thank you for posting this tutorial, you will make a lot of people happy!

One MAJOR thing I want to point out, the reset line (normally DTR) MUST be connected to the micro USB shield, or it will not work! The first few micro USB cables I found around the house, either did not have a shielding connected to the micro USB shield, didn't have one at all, or for some reason it was also connected to GND or something else (can't remember, had to tone it out to check).

So just keep that in mind if your custom made cable isn't working. I started on a tutorial that actually goes through creating your own micro USB cable, here's the link to it (it's incomplete), but i'll try and finish it as soon as possible: ... mer-cable/

Hopefully everyone finds a cable that has it connected to the shield because that makes building one SOOO much easier!! Making this a sticky!

Re: DIY Programmer Cable

Thank you all for the feedback!

I have some GREAT news, my DIY cable works with the OSM2s I just received. Was able to do an EEPROM wipe and NEO install without major issues.

If you get a "programmer unresponsive" error when attempting to upload an arduino sketch, try swapping the TXD and RXD wires.
If you still get this error, try connecting with batteries inserted and wipe the EEPROM and re-upload NEO.

This is the FTDI Programmer I purchased off of AliExpress:

While it is cheap, I would advise you source one stateside unless you want the delivery time to be "eventually"

Here is the USB driver for this particular FTDI Programmer:

If you get an FTDI Programmer that isn't the exact same model as the one used in the original programmer cable or the one listed here, you may have to go driver hunting. Punch in the model number into your favorite search engine and it shouldn't be long till you find the correct driver.

Again, once installed, you can follow the other tutorials without problems.
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