Suite of Linux command-line utilities for communication between the calculator and the PC via the calculator serial port.
Some Casio calculators, including fx-7700GB and fx-7700GE, have serial interface with 2.5mm stereo audio plug for exchanging data with other calculators and PCs.
- The communication line carries RS-232 TTL signal, the voltage is 5V for older models and 3.3V for newer models;
- Data rate is 9600 baud by default, but can be set also to 1200, 2400 and 4800 baud. It is fixed to 9600 on newer models;
- Parity is by default set to Even, but can also be set to Odd or None. It is fixed to None on newer models;
Casio provided optional cables for connecting two calculators, part numbers SB-60 or SB-62, and also optional battery powered level-shifter kits for connecting the calculator to PC via native serial interface, part numbers FA-100 or FA-121 and maybe also others.
This suite of utilities was written to enable the communication between the Linux PC and the calculator. It should work with any suitable serial device that has compatible voltage levels. However, testing has been done only using the FTDI TTL-232R-5V-AJ cable with the fitted 3.5mm to 2.5mm plug converter. The converter has to have tip and ring connection crossed.
Hardware used for testing:
| Calculator | FTDI TTL-232R-5V-AJ |
|---|---|
| Tip | Ring |
| Ring | Tip |
| Sleeve | Sleeve |
The utilities were tested and will work with fx-7700GB and fx-7700GE models for communicating only programs. Only monochrome screendump was tested to work with CFX-9850G. To be clear, no other data communication functions are currently implemented, as the utility is written primarily for Casio fx-7700GB. The latter has the functionality to transmit and receive programs only.
The utility suite is written for Linux. For creating binaries, run 'make' in the project root directory. Binaries will be built into 'build' subdirectory. Run 'make clean' to delete the files created during building.
Three binaries will be built:
casio_rx - utility to receive data from the calculator. Running the utility will set the PC into state of waiting for the calculator to start the transmission.
casio_tx - utility to transmit data to the calculator. Running the utility will start transmission to the calculator. Calculator has to be already in receiving state
cas2pbm - utility to convert CAS formatted screenshot from the caclulator into PBM P4 image.
All three utilities will output details about how to use them when run without the command line arguments or when started with -h or --help command line option.
The utility communicates with the device over a serial interface using a specific section-based protocol. Main stages:
- Handshake and synchronization
- Header data block transfer with checksum verification
- Error handling
- Optionally followed by more data blocks and error handling, depending on the type of the header
More specific description: PROTOCOL.md
The description of the sections structure: CAS_FILE.md