2020 - Rogerio Altmeyer
This EEPROM programmer was born to support the development of another retro-computing project that I'm working on, where the focus is to recreate computers from the 80's from scratch in a modular construction and compatible with the original binaries.
The programmer was created with the ATMel's 32Kb EEPROM AT28C256 in mind, and at this time the firmware is only compatible with this chip, but can be easily converted to other parallel memories.
The project is divided into three parts:
- Schematic design and Circuit board design (Hardware).
- Board Firmware (C++)
- Client that runs on the host machine responsible for communicating with the board (Python)
The board uses the Arduino Nano as the main component, responsible for communicating with the host computer and programming the memory chip.
The control bus and the data bus are connected directly to the Nano, and the 15 addressing lines of the chip are fed through two 8-bit shift registers connected in sequence.
Schematic for the Board V1.3
The board design is available on a ZIP file with Board Gerber. I used the board print services from JLCPCB.com and I recommend it.
The board's firmware was developed in C++ using the Eclipse IDE, and its main feature is the implementation of a message interpreter from the host computer. With the message interpreter, it was possible to organize the code for new features to the firmware.
- 28c_programmer.h Main header
- pin_defs.h Header with pins definitions
- main.cpp Main source containing the functions setup() e loop()
- interface.cpp Contains all the functions for the interface between Arduino and EEPROM
- util.cpp Miscellaneous code support
- cmd_processor.cpp Implements the message interpreter
- cmd_clear_block.cpp Function to clear EEPROM
- cmd_get_version.cpp Function that returns the card's firmware version
- cmd_read_block.cpp Function that reads a 16-byte block and returns it to the host
- cmd_read_byte.cpp Function that reads 1 byte
- cmd_write_block.cpp Function that writes from 1 to 16 bytes to the EEPROM
Written in Python3, this layer is responsible for read/write files on the host machine and send/receive to/from the board's firmware.
To run the client, you must have python3 and install the following dependencies:
pip3 install argparse
pip3 install pyserial
You will also need to adjust the permissions:
chmod +x programmer.py
The client will show the following help indicating the supported parameters:
#./programmer.py
usage: programmer.py [-h] [--file FILE] [--address ADDRESS_BEGIN]
[--address-end ADDRESS_END]
serial {write,read,clear}
programmer.py: error: the following arguments are required: serial, mode
Required parameters:
- Serial port
- operation mode
- write
- read
- clear
Optional parameters:
- --address The start address for the operation
- --address-end The final address for the operation
- --file Required for write and read modes, the file to be read/written
Write the boot.hex file to position 0x0000
./programmer.py /dev/porta_serial write --file boot.hex
Write the data.hex in position 0x1E00
./programmer.py /dev/porta_serial write --file dado.hex --address 0x1e00
Read the entire EEPROM to the dump.bin file
./programmer.py /dev/porta_serial read --file dump.bin
Read from EEPROM from the address 0x1E00 to 0x2A00 and create the dump.bin file
./programmer.py /dev/porta_serial read --file dump.bin --address 0x1e00 --address-end 0x2a00
Clear the entire EEPROM (write 0xFF in all memory locations)
./programmer.py /dev/porta_serial clear
Clear an EEPROM block
./programmer.py /dev/porta_serial clear --address 0x1e00 --address-end 0x2a00
Board version 1.3 - 3D view
Board version 1.3
Board version 1.1 assembled
