T41-3 Main Board: A Mundane But Useful Change

There are few annoying things about the T41 Experimental Platform. However, there is one big hassle. That is the Teensy plus Audio Hat “stack”!

This contraption of Teensy and Audio Hat requires so-called “stacking headers”. It is more difficult to assemble than the typical module used in the T41. It is also mechanically unwieldy and makes the total height of the Main Board almost 50mm. Here is a photo:

Recently I noted two instances of Teensy plus Audio Hat which are not stacked. Here is the Proto Supplies “Prototyping System For Teensy 4.1”:

https://protosupplies.com/product/prototyping-system-for-teensy-4-1/

Another example is the KeithSDR:

https://github.com/K7MDL2/KEITHSDR/wiki/Hardware

So clearly it is possible, and the next question is why didn’t anyone do this for T41 before? Perhaps there is not enough room on the 100x100mm board?

This turned into a “mini-project” and a new variant of the T41 Main Board. It is in fact possible to fit the existing modules and the Audio Hat onto the Main Board, dispensing with the “stack”. Here is a photo of the prototype without the modules:

And with the modules:

There are only a handful of connections between the Teensy and the Audio Hat. The Audio Hat headers are 14 pins so there is a total of 28 pins shared with the Teensy. However, only 7 pins are actually required to be connected. This made the re-wiring of the Main Board quite doable. Not easy, but the layout proceeded quickly enough.

Does it work? YES. Preliminary testing shows the new prototype to be working just fine.

Conclusion

Disadvantages? There is only one found so far. It is not possible to plug a headphone into the Audio Hat. The PCM5102 module interferes. I have two different ways to fix this problem. I will be working on this problem soon and will edit this blog with the changes when it is completed.