Raspberry Pi In A Ti-83 Plus

[ecefour]

Hello everyone! A few weeks ago I posted here about my Raspberry Pi Zero inside a Ti-83 Plus graphing calculator (Retropie emulator). If you haven't see it you can read about it here: http://www.sudomod.com/forum/viewtopic.php?t=4116. It works great, but needless to say it was missing a few features. For example there was no headphone jack, and the buttons were all wired though the GPIO pins instead of a Teensy, not to mention the screen didn't fit that well. Unfortunately there doesn't seem to be enough space to fit any of those things in there. So it became obvious the only was to achieve those things was to create a PCB similar to Helder's AIO board for the GameBoy Zero. My board for the calculator will hopefully include a internal USB hub, a Atmega for the keypad, and a builtin 2.4" or 2.8" screen (Similar to the one on the Mintypi). Later I would add things like a switch for the audio (internal speaker to headphones), and a builtin battery indicator / charger. What do you guys think? If no one cares I will just make a few for my friends and I. But if anyone interested please tell me. The price will likely be in the $40 / $50 range (plus shipping).

[moosepr]

I personally wouldn't buy one, I have way too many pi projects on the go, but it's a fun project.

You can get access to 22 gpio pins for buttons, or you can use alternative methods like specialist keyboard matrix chips which can give you up to 80 keys using i2c. If you are planning on using eagle for the PCB design, I have libraries for the ili9341 screens

[ecefour]

Last time I did use the GPIO pins for the keyboard. Though it was a pain to get them working under other operating systems like Kodi. I just figured a USB controller would be easier. Thanks for the feedback.

[moosepr]

I personally prefer to avoid the usb, then you don't need to add a hub. I'm working with a tca8418 chip on a pi/keyboard project. It's a pain to solder, but hopefully it's useful

[ecefour]

That is true, But I was going to also use a USB port for a sound card. So then I could use an extra USB port from the hub to connect peripherals like an external keyboard or mouse. It would also be good for transferring roms. I could use a GPIO pin as an audio output, but would require even more software setup. What do you think about using GPIO as a audio output? Is it a pain to setup or am I just overreacting? Thanks!

P.S. Currently I only only plan to get about 8 keys working for things such as Retropie. But I'd love to see the I2c keypad project your working on.

[moosepr]

well you can use PWM audio, simple setup (1 line in config.txt), but is known to be noisy and needs an amp. Or there is i2s, which is harder to setup, but gets much better audio quality.
PWM needs 2 pins, i2s needs 3

that will still leave you with 20 or 19 pins left for buttons, and then the usb is free for external usage

[ecefour]

Thanks for the help the suggestions! I'll look into it.