Programming Applications

There are many great guides online to get started with developing Android apps. To get started programming on the Kindle Fire, we recommend you follow Amazon’s instructions here: https://developer.amazon.com/sdk/fire/setup.html

Once you have Eclipse for Android up and running, you can download our demo code from the GitHub repository and get started developing for the TPad Fire.


Programming Firmware

The PIC microcontroller on the electronics board needs to be programmed with custom firmware. You can use the free IDE MPLABX (http://www.microchip.com/pagehandler/en-us/family/mplabx/) and our MPLABX project plus a PICKit3 Programmer to do the job.

It is recommended that you use version 2 of the firmware: https://github.com/TPadTabletProject/TPad-Fire-Firmware-v2

Testing and Tuning

The first step to getting the TPad Fire up and running is to ensure that it is tuned adequately and everything is running correctly.

Testing Communications 

First check to make sure the USB communication is working correctly.

  • Turn on the Kindle Fire.
  • Once it has loaded to the home screen plug in the USB micro connector from the circuit board and turn on the main battery.
  • A USB Transfer screen should appear on the Kindle. It should say “You can now transfer files from your computer to Kindle”
  • Hit “Disconnect” at the bottom of the screen. This should take you back to the home screen.

If you get the USB loading screen to come up, this means the TPad Fire communications are working!

If you are not getting this screen, check out our forums and feel free to post a question.



  • The next step is to tune the TPad correctly. For this you will need the TPad Calibration App, which is on our Github. Version 1 is for the first version of firmware, while version 2 is for a later version of firmware. Load the appropriate version. Ask on the forums if you aren’t sure which version you have.
  • After loading the TPad Calibration App the TPad should start turning off and on at approximately 10Hz. This is normal. You will use this to gauge how strong the TPad feels as you adjust the tuning frequency.
  • Adjust the frequency by touching the different numbers on the scroll bar at the bottom of the screen. The “Current Frequency” should change each time you hit a new number.
  • For each frequency, run your finger along the text that says “Feel Here to Test.”
  • After trying out a bunch of different frequencies, you will need to make a subjective guess on what feels the strongest!
  • Once you have made your decision, use this frequency in all of the apps you develop with your TPad Fire.

Adjustment Capacitors                 

If you want to get more performance out of your TPad Fire, you can use different capacitors from the default values (the default values are 10nf+3.3nf = 13.3nF). After determining the best frequency using the procedure above (and using the default values), you can calculate new values according to the formula:

Cadj = 1/(4 * Pi^2 * Lamp * ftpad^2) – Ctpad


Lamp = 390*10^-6 (this is the inductance of the amplifier inductor, about 390uH)

Ctpad = 44*10^-9 (You can also measure the exact capacitance of the TPad, it should range from 40-50nF)

ftpad = Tuning frequency determined from above

With the new Cadj values in hand, simply remove the default ones and replace them. If at all possible, try to get higher voltage capacitors (50V and up) here since they will have around 100V AC across them.

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