Hello everyone!

This is not a tutorial anymore!
Also please help finding a better name.

I'm building a Raspberry Pi A+ into TI-84+.

(old, obsolete): Have a look at my current progress.

My shopping list was:
- TI-84+
- Raspberry Pi A+
- Arduino Micro Pro
- USB power bank
- USB hub
- Multiple USB-Micro cables
- TFT (itdb240)
- USB-A jack
- Small power switch
- a small piece of stripboard (or perfboard)
- a small piece of foam
- a micro sd
and more stuff

Total cost: around a 100 - 150 euros / dollars

I already drilled out most of the calculator cases spacers and the battery department. Also I wired up the matrix to my arduino micro pro and im working on the scanning code.

Out of curiosity, is ther a reason that the Raspberry Pi A+ wouldn't be an option for this?

I haven't heard anything about the A+ before.
Thanks for pointing it out, but the A, (A+ << forget about this), and as I just checked also the B one have way to few pins for the whole matrix scanning.

If you add two 74-series logic chips, you actually only really need 8 pins to scan the keyboard matrix: does the Pi not have 8 spare GPIO pins?

You're right. But if I go for the TFT I need all A or Bs data lines for parallel communication. But with the 83+ LCD and the Logic chips I could get it to work on Raspberry Pi A and A+. Not on the standard B as it draws about 700-800mA compared to the B+, which draws 500mA and the A with 400mA

The model A+ has the same number of pins as the B+

Ok, I'll correct me. Sorry for my missinformation.

*bump* Out of curiosity, do you have any updates for us on this project? I just ordered myself an ODROID-W development board to try to make my own version of this project.

Hola!

I have an update for y'all!

The display is now finally installed and working. ;D
I have also drafted the schematics and ordered the missing parts.

Let's get this one made!

I have a feeling this is going to be called the "TI-84 Minus" by somebody.

Hehe.
Well the name changed to Pi84 a while ago.
I am trying to get programming of the system controller done soon.

Benedikt

I have been very busy lately, developing a complete replacement PCB that will fit into the empty shell of a TI-84+.
It features an ATmega328P-AU Arduino Uno compatible keyboard processor and power management controller and real time clock (to keep the time running, while the Pi is turned off).
This will be a two board solution. There will be an upper and a lower board.
On the upper board, there is space for fitting a Raspberry Pi Zero (W) and a 128x64 monochrome/grayscale LCD that I would provide. The bottom half of the board (including keypad matrix, RTC, Uno and the Adafruit PowerBoost500 for LiPo operation) will be attachable to the upper board through a few solder links. Therefore you can decide whether you want to provide your own single board computer or if you want to go for a Pi Zero and my preferred, matching LCD.
The headphone/Link jack will either expose the Pi Zero's analog video signal plus one GPIO pin or the I2C bus, depending on solder jumper configuration. The Uno is connected to the Pi via SPI and UART. You should be able to reflash the Uno from the Pi, if you disable the Linux console on the serial port.
Otherwise, the serial console will be displayed on boot in a serial terminal mode of the Uno.
The Uno is also connected to the 128x64 screen and will go into high impendance mode to let the Pi access the screen, once the Pi is booted and ready.

I guess I can already warrant a sneak peak at the keypad matrix


I hope there is demand, and if there is I may offer a kit or the bare PCBs.
If someone does not like to solder SMD, I could also offer individual assembly of the boards.
There is also need for a good name. Please post any suggestions.