Homebrew Programming Cable for the Motorola XPR Series Mobile

We are happy to have a guest post by Rich, KG5RGB. Thank you Rich for making DMR better by sharing this article with the Texas DMR community.


Here is an easy and satisfying one evening project for those that have a Motorola XPR series DMR mobile radio. This project isn’t particularly ground breaking, as others have provided some of the basic info. But I did want to share my experience of home brewing a programming cable with the Texas 3148 DMR family.

We all know some of the bits and pieces associated with our hobby can nickel and dime our precious radio budgets, but here is one dollar saving project that also allows you to keep your soldering and kit building skills honed. I spent a grand total of $5 on this project. You may spend a bit more if you can’t find an old USB cable to donate to the cause.

As awesome as the Motorola XPR series is, the cost of programming and accessory cables can add up. Recent searches for OEM Motorola XPR cables returns prices as high as $70. EBAY and Amazon lists aftermarket programming cables for around $20-$30. After spending hard earned hobby cash on a professional grade DMR radio, it may be scary to trust your radio to a sketchy EBAY programming cable. Who wants to brick a radio?

After digging a bit for alternatives, I found that compared to some previous generation Motorola radios, the programming cable for the XPR mobile series is quite surprisingly a simple affair built upon the common USB format we are all familiar with. So simple in fact that any standard USB cable interfaces directly to the rear accessory connector! No RIB box, serial to USB convertors, no nonsense. How refreshing indeed.

Project Supplies

  • Soldering iron/solder
  • Motorola accessory connector kit #PLMN5072A
    • Wiscomm.com for $4.99 plus shipping.
  • Surplus USB cable (any cheap USB cable will do)

The connector kit comes with the semi-proprietary Motorola 26 pin connector, 27 pins, a pin removal tool and a zip tie to provide strain relief for whatever cable you decide to use the connector for.

Cut off and strip whatever end is on your USB cable, leaving just the computer side of the cable. You should be left with 4 wires, Red, Black, White and Green. Strip, twist and tin the 4 wires in preparation for soldering to pins.

Clip 4 pins from the pin sprue, and solder the 4 wires to the silver side of the pins. You may want to carefully crimp the soldered side to close the end which will make the pin easier to slide into the connector housing.

Once you have soldered the pins, you can begin inserting the pins into the rear of the connector “gold” side first. The USB wire to connector position orientation is as follows:

  • PIN#1 = Green USB wire
  • PIN#2 = White USB wire
  • PIN#3 = Red USB wire
  • PIN#4 = Black USB wire

In this photo you can make out the pin identifiers embossed on the connector (2 on the right, 26 to the left). This pic shows the 2-26 pin side, the bottom row (in this photo) will be the 1-25 pin side.

Note the orientation of the pin relative to the hole in the connector. It only fits one way, and you will know if you have fully inserted the pin when you hear a satisfying “click” letting you know that the pin is fully seated and locked.

Don’t panic if you accidentally insert the wrong pin into the connector. The pin removal tool is provided in the kit for exactly that purpose. This is what your connector should look like once you are done.

While I was at it, I did throw some pins on one of my Motorola external speakers and made an “all in one” speaker and programming cable. This allows me to install the mobile in my truck, and hide the USB cable for laptop reprogramming. And let me tell you, that external speaker can SING! Doors open in a field, engine running, and wind blowing I can hear all the Texas DMR chatter from 100 yards away out of the mobile!

For external speaker connections, you want pins 9 and 10.

This was a very satisfying project for me, and I hope sharing this saves a couple of you a few bucks. The final picture shows the initial codeplug read using the homebrew cable proving that the ole’ soldering iron still has a place in this plug and play world.

73 from Rich KG5RBG!