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• Recognising the free form text written on the cap-touch pad

  kunal.t2 • 08/21/2014 at 13:17 • 0 comments

  The idea of replacing the expensive touch screens using cheap capacitive touch pads, for free-form text input is quite interesting. However the challenge lies in identifying what the user has written on the touch pad.

  To solve this problem I plan to use an implementation of M.Turk and Pentland's classic paper titled "Eigen Faces for Recognition"

• User Input

  kunal.t2 • 08/21/2014 at 13:08 • 0 comments

  I plan to use a matrix of 20 x 20 capacitive touch pads which would be scanned sequentially. To get a 20 x 20 matrix of on/off data.

  Something like the illustration shown below on a 5 x 10 matrix

  0010000100

  0010000100

  001 1 1 1 1 100

  0010000100

  0010000100

  If you observe carefully, I have written a capital "H" in the bit field above.

  The idea is to draw inspiration from the slate and provide the user with a writing area where he/she can write anything. Numbers / English Alphabets / Hindi Alphabets / Kanji ( Chinese ) Alphabets etc. What ever the user writes is scaled and displayed on the Nokia LCD. This is the Unique Selling Point of this device. ( To replace expensive touch screens with a cheap cap-touch matrix )

  Along with the above, I also plan to have a "Submit" and "Clear" Push buttons to allow the user to "Save" the bit field, or clear the bit field respectively.

• Power Consumption

  kunal.t2 • 08/21/2014 at 13:00 • 0 comments

  The pinoccio dev board consumes around 17mA when running at full blast. ( From the faq page of pinocc.io )

  The Nokia 5110 LCD module would take around 40mA with the back light LED on.

  Assuming I use an 8 Ohm ,  0.5W speaker. I would consume around 250mA

  Adding a buffer of 20mA for other components.

  Totally we have around 330mA.

  So, all the above would be easily powered using the 550mAh battery supplied with the pinocc.io dev board for atleast an hour.

  Given that the speaker would be used intermittently and the back light LED of the LCD module would be used only at night. We should still be able to get around 4 or 5 hours of usage from this device on a single charge.

• Basic Idea

  kunal.t2 • 08/21/2014 at 06:18 • 0 comments

  So, the basic Idea of the build would be to get each component of the project working separately.

  I have a couple of pinocc.io dev boards and to get them to work in a P2P configuration would be trivial. 

  I have run the lcd display and the mp3 decoder + 8 Ohm speaker using pre-existing arduino libraries.

  The only part that I need to work on is the 20 x 20 touch pad. I want to check if the touch pad can be driven using the pinoccio itself. That way we can avoid the STM32F4 altogether.

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