serisman/ch55xgraylink

An Arduino (Ch55xduino) sketch for CH551 or CH552 MCUs that makes it possible to connect a TI calculator to a computer over USB.

CH55xGrayLink

A sketch for CH551/CH552 based Arduinos (using Ch55xduino) that makes it possible to connect a Texas Instruments calculator to a computer using USB.

Introduction

This sketch allows a computer to connect to and transfer data to/from a TI graphing calculator over USB. It is a port of the serial2ti83 Arduino sketch for Arduino Nano/Uno found here. In order to use it, compile and upload CH55xGrayLink.ino to a CH551 or CH552 Ch55xduino board using the Arduino IDE.

Sketch uses 4254 bytes (41%) of program storage space. Maximum is 10240 bytes.
Global variables use 59 bytes (16%) of dynamic memory, leaving 305 bytes for local variables. Maximum is 364 bytes.

Wiring

Connect the following pins to the 2.5mm port located at the bottom of the TI calculator according to the following table:

2.5mm port	CH55x
tip	P1.4
ring	P1.7
sleeve	GND

Transfer Speed

Max reported transfer speed seems to be about 3.2 KB/s based on testing done to date (TI-83 Plus).

Arduino Settings

First, install Ch55xduino according to the instruction found here: https://github.com/DeqingSun/ch55xduino#installation

Then, select the CH551 Board (or CH552 Board) and adjust the other settings to match below.

Adjust Port as needed. May need to use Device Manager to force the port to COM1-4 for TI programs to actually see it.

Schematic

PCB

Designed to fit within a standard USB-A male port housing.

Gerbers: pcb/output/gerber.zip

PCBs available from: OSHPARK

Finished Cable

Note: This is picturing an older PCB (from a different project), but the optimized PCB available above is basically the same thing.