Since version 1.2.2 MiSTeryNano the firmware for the M0S/BL616 MCU has an additional IRQ connection to the FPGA for faster response times.
Beginning with version 1.2.0 the connection between the M0S MCU and the FPGA is a SPI bus. The wiring is the same as with the PS/2 variant but the signals are used differently.
With the SPI bus the M0S was no longer limited to to keyboard and mouse. Instead it also took over the SD card file system handling, the control of the on-screen-display and various other tasks that are not directly related to the retro machine itself.
Version 1.1.0 implemented a PS/2 like connection to send the keyboard and mouse data from the BL616 MCU into the FPGA. All configuration was done via connections on the board.
Since version 1.2.0 configuration is done via the OSD.
The MiSTeryNano up to 1.0.1 implemented some basic mouse control via five digital direction inputs on the Tang Nano 20k which needed to be switched to GND.
Alternally a Blackberry
Trackball could be
used on the same pins. In this case the TRACKB config switch
needs to be closed.
The code is still in the main repository and can be activated in src/tangnano20k/top.sv.
Since 1.1.0 mouse and keyboard are connected via USB and a seperate MCU.