isablaster

ISA Blaster

A PCB for a software-defined ISA card powered by a Raspberry Pi Pico micro-controller. All the logic for interfacing to the ISA bus is done in software.

Projects based on the ISA Blaster

DirtyRat USB Mouse Adapter

We can use the ISA Blaster as a USB mouse adapter card. This allows you to use a USB mouse on your vintage DOS PC without the need for an external adapter. This requires the use of:

1. The DirtyRat mouse driver for DOS: https://github.com/scrapcomputing/DirtyRatDriver, and
2. The DirtyRat Firmware for the Pico: https://github.com/scrapcomputing/DirtyRatFirmware.

How to load the firmware

• Unplug the ISA Blaster from the motherboard
• Remove any connected USB devices (e.g., mouse)
• Press and hold the small button on the Pico
• While holding the button, connect the Pico to your PC with a micro-USB cable
• The Pico should show up as a mass-storage device
• Copy the firmware to the drive associated with the Pico
• Safely eject the mass-storage device

Bill of materials

Gerber files are published in the releases: https://github.com/scrapcomputing/ISABlaster/releases

Item	#	Description
Raspberry Pi Pico	1
1x20-pin 2.54mm Female Headers	2	For plugging in the Pico
1x20-pin 2.54mm Male Headers	2	For the Pico
TXS0108EPW 20TSSOP	3	Bidirectional level-shifters 3.3V/5V
2x6 2.54mm Male Pin Headers	1	For the IRQ selection
2.54mm Jumper	1	For the IRQ selection
0.1uF 1206 SMD capacitors	6	Decoupling capacitors for the ICs C1-6
2.2K through-hole resistor 1/8W	2	* Better to leave them unpopulated: See "Known Issues" below
3.3K through-hole resistor 1/8W	2	* Better to leave them unpopulated: See "Known Issues" below
1uF through-hole ceramic capacitor	1	Smoothing capacitor for the board.
Horizontal Female USB connector	1	For plugging in a USB device.
3-4cm short jumper wires	2	For connecting Pico's TP2,TP3 pads to the PCB's pads for the on-bard USB connector

Known Issues

• Rev0.1 connects MEMR and MEMW to voltage dividers which are made up by the 2.2K and 3.3K through-hole resistors. The voltage dividers can cause issues on some motherboards, so it is better to leave them unpopulated. This will be fixed in a later revision of the board.