Pogo Pin Programming Intro
In our previous series, Programming for PCB Production, we provided an overview of different methods to program PCB products. So far, we’ve covered how to design and build a simple programming fixture. In this article, we’ll cover how to design pogo pin programming cables for faster production programming. This coincides with our release of Tag-Connect footprints for Eagle. Other EDA tools will follow!
Tag-Connect Cables and Footprints
Pogo pin programming cables are essentially pogo pins molded in a handle that connects a programmer to the device to be programmed. They are similar to a full-on test fixture like we designed in the last article, but are more flexible since they are not designed specifically for one PCB. Tag-Connect is the supplier we like to use here at MacroFab for these kind of projects.
Figure 1 shows the end of a Tag-Connect cable. These kind of cables are great for low volume production programming since there is no cost in designing and building a fixture. You also save in not having to populate a part for a programming header saving in the BOM costs and assembly labor. The downside to pogo pin programming cables compared to a full-on fixture is that you still need to apply power to the board that is being programmed but this can be addressed in some cases.
Tag-Connect carries several different cables that can connect a wide variety of programmers to your project and MCU. There are three different connector sizes:
• The TC2030 is a 02 x 03 (6 Position) connector,
• The TC2050 is a 02 x 05 (10 Position) connector,
• The TC2070 is a 02 x 07 (14 Position) connector.
Figure 2 shows all the different sizes Tag-Connect offers. For these connectors there are two different sets of legs. Tag-Connects without locking legs (shown above in Figure 1) and Tag-Connects with locking legs. The locking legs are useful for prototyping as you don’t need to hold the connector in while programming which makes it easier for debugging. The downside to the locking legs is that they take a bit more room then the non-locking legs version and are a bit more fiddly to use while in production. In the MacroFab parts libraries we have pre-built footprints (see Figure 3 for an example) for the TC2030, TC2050 style connectors as these are the most common. For Eagle they are in the MF_Connectors.lbr library under CON_02x03 and CON_02x05.
Using Tag-Connect Cables
To use the Tag-Connect cable you just line up the locating pins and press it into the board. If you are using the no locking legs version you must hold it until programming is done (See figure 4).
In the next article, we’ll go over how to adapt your design to use a Tag-Connect cable by building up a small AVR based PCB and program it with ISP over a Tag-Connect cable.