Sunday, June 8, 2014

Teensy 3.1 & The RESET Pin

The Teensy 3.1 unlike the Teensy 3.0 does not have a RESET pin to which you can connect a header and access it easily. The 3.1 has the RESET pin at the bottom of the board connected to a very tiny circular pad - the reason being, as Paul Stroffregen says, is to keep the board in a small form factor. For breadboarded projects it is kinda impossible to tap into this pin and have reset functionality available. The only source of a reset is to power off and power on the device. Another method is to connect a wire to the reset pad and if you succeed you get the reset functionality. I however do not like wires dangling about and creating a mess on my breadboarded / PCB projects, also they have a higher chance of breaking off. In this post i describe how i dealt with this situation of accessing the reset pin...
Here is the Teensy 3.1 boad with it's RESET pin marked as R on the bottom of the device. 

Take a female header pin connector - the kind of connectors you find on Arduino / shields. You can either get a single female header or break one off a 8-pin header like i did to mine.

Place the header on the board and fold it's pin such that it forms into a shape shown below. Try to make sure that you fold it enough such that the lower curved end and the plastic section of the header are in a straight line otherwise you will find that when the header is placed flat on the board it will start to rock on one side...

Clip off the remaining end of the connector after aligning properly with the board. I placed the header near the board edge right below the USB connector.

Time to solder the header. Place the header on the board and use some tape to fasten it when you solder, thereby preventing it from moving around and getting a dry / nasty solder joint. Try to keep the tip of the header near the center of the pad.

This is what it looks after soldering. The header lies flat on the PCB and the joint is far from breaking off.

The female header is the same size as the male header pins. It can therefore be easily used with a breadboard.

That's it, now you've got a access to the RESET pin in a more respectable manner :P. However, the disadvantage of this approach is that you lose access to the +D pad and cannot connect the capacitor for USB host mode. I never intend to use those, hence no regrets. Make sure to glue the header to the board with some strong adhesive.

Got a better way ? Post it in the comments below and let me know. 

Thanks for reading through....


Marmil said...

Thanks for showing how you did this excellent little fix. I still have a few Teensy 3.0's left, but once I've used those up and get some 3.1's I'll definitely try this.

JWHITTEN said...

You could also use female headers which are longer than required and then bring out a wire to one of the extra pins. You could also bring out additional lines from the bottom of the board that way. If the Teensy is going to be used primarily on the breadboard this would be a reasonable approach.