All the bits are here.

 
 

5V and charging from USB, now I’ll need one of these..

This is the Adafruit PowerBoost 500 Charger. It will charge your little Lipo battery from USB, power your project from either USB or battery and it has an input for a power switch. Basically everything you’d ever need.


Now just to fit it all in.

 

Suddenly the RAM issue was solved!

Original calculator running on a Teensy

I had the touchscreen, and I had code from the eye project showing how to run the screens from the Teensy.  Turns out it was exactly the same as the Arduino. Just a lot faster.


First was to see if I could run the bigger touch screen from the Teensy. Turns out, with some tweaking to my screen library, I could.

When I’d worked on this before, I’d created the beginnings of a c++ framework to run a user interface in the background leaving the main coding open for the usual Arduino things people do. Add some sensors, LEDs, switches what have you. It was time to revisit this and do a total rewrite of a lot of it.


And it worked! The toolkit I wrote allows you to have a touchscreen interface with just a couple lines of code added to you Arduino sketch. And it all runs in the background during idle time.


Once everything was running on a USB cord it was time to make some decisions. It would be nice if it was battery powered and rechargable from a USB cord. This means a battery charger circuit. Also, the battery is only 3.7V but the screen wants 5V. This means a power converter.

 

Shopping list of the bits used :


The touchscreen : https://www.adafruit.com/product/1947

The power system : https://www.adafruit.com/products/1944

The power switch : https://www.adafruit.com/products/805

The battery : https://www.adafruit.com/products/1578

The processor : https://www.adafruit.com/products/2756

The beeper : https://www.adafruit.com/products/160

The screws : https://www.boltdepot.com/Product-Details.aspx?product=6363


Fine 24-30 awg silicon wire. You’ll need it fine and flexible.