The OpenM128 was one of my favourite AVR development boards but sadly it doesn’t seem to be made any more by Waveshare.
This board looked like this
It was a very useful board which had a few on board features and all of the ATMega128 ports went to external headers. you could connect your own sensors or there were various add-ons
It featured the ATmega128A-AU
Which in turn has
Core: AVR 8-bit RISC
Operating Frequency: 16MHz Max
Operating Voltage: 2.7-5.5V
Memories: 128kB Flash, 4kB SRAM, 4kB EEPROM
Then there were the following
8 LEDs: convenient for indicating I/O status and/or program running state
5 push button switches : for I/O input test and/or program control
Joystick: which had five positions
Headers for onewire, usart, i2c, lcds, ps2 keyboard, jtag and more
We have uploaded all the source code for various demos to the link below, we have tested a few out and you can import them into Microchip Studio 7, build them and using a programmer you can upload to the board.
We setup a USBTinyISP and that worked perfectly – the board has a 10 pin and a 6 pin ISP connection – either work.
Uploaded the code examples and schematic here – just in case the waveshare link disappears