To get the true Pi zero experience in your pocket, we are gonna need some buttons!!
so i have been playing with the buttons, and the placement of them, and im sure i will come to regret this!!!
my biggest hurdle was trying to turn the 10x7 array that the TCA8418 can provide, and convert that into the 14x5 'standard' keyboard layout that most people use every day (one row of numbers, 3 rows of letters, and a row for crtl/alt/super etc)
I finally sussed it, chop to 10 in half and rotate each side 90 degrees in the opposite directions. Then placing the TCA8418 in the middle of it all and were getting there!!!!
A quick run of the autorouter shows me it will work better this way, i need to spread the buttons more ans other fun. get the feeling i am going to be sick of these buttons by the time i am done with this
So i have been pondering the screen. The 2.8 inches wont reallly cut it for photo editing or word processing, but its ok for quick bits of hacking, or basic coding.
if any of you have used the cheap resistive touch overlays that these small screens come with, you will know that they are not the greatest. inaccurate, unresponsive, pretty naff really.
so im going to make a decision, and negate the touch, removing the need for another conroller chip, and another driver.
maybe some mouse emulation on the cursor keys (nav switch) might be a good way round it...
After a bit of a chat with Wai Lun I am now aware of a few projects which use the TI chip TCA8418. For those of you who are unaware of this chip (as i was 24 hours ago!) it basically handles the 'keyboard' duties of a project, including scanning the rows/columns for keypresses, debouncing, and all the other things that can make keyboards hard to implement. As an extra bonus, the pi communicates with the device via i2c, meaning that up to 80 buttons can be added to the pi, using just 2 pins!! that is a mega plus!
I have added a little bit more to the board, namely the TCA8418 chip, battery socket, and the charge/protect module i have used in the past. nothing is linked, so again DO NOT ORDER THIS!!
So i want to try and keep the 2.8" screen (currently without touch) and try and keep the best keyboard experience.
The Keyboard i am currently using (model M of course) has 14 keys across most of its 5 rows, so a 14x5 matrix would only use 19 of my 22 free gpio pins (result)
the next problem is to see if 14 buttons will fit across the space beneath the screen. I fired up the eagles, and lo and behold, i could just about squeeze them in, JUST!!
clearly nothing is actually connected yet, there isnt even any board bounds on there, just a pi, tft, and 14 buttons. Looks like this could work....