DirtyRat Firmware for the ISA Blaster

This is the firmware that needs to be loaded to the Raspberry Pi Pico of the ISA Blaster to get it to work as a USB Mouse adapter. The DOS driver for this is the DirtyRat Driver.

Download

Binaries are available in the releases: https://github.com/scrapcomputing/DirtyRatFirmware/releases The file to be loaded to the Raspberry Pi Pico is the one with the .uf2 file extension.

How to use

The firmware is configured to use 0x2e8 I/O address by default, which usually overlaps with the 2nd serial port COM4. So please make sure that you disable the conflicting port on your PC.
Load the firmware to the Pico (see instructions below)

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 .uf2 firmware to the drive associated with the Pico
Safely eject the mass-storage device

Build

Dependencies:

Pico SDK 1.5.0. Please adjust the PICO_SDK_PATH in src/CMakeLists.txt
C++ 17 or later compiler
CMake 3.13 or later
Recent version of make or other build system supported by CMake

Build instructions

Create a build directory and cd into it: mkdir build && cd build
cmake ../src/
make The firmware should be in build/DirtyRatFirmware.uf2.

Build Options

You can override some of the default firmware options:

Specify the I/O Address with cmake -DIO_ADDR= (Default is 0x2e8)
Specify the Pico CPU Frequency with -DPICO_FREQ= (Default is 133000)
Specify the USB poll period in milliseconds with -DUSB_POLL_PERIOD= (Default is 25)

For serial debugging the Pico you need to specify -DENABLE_SERIAL_DBG=1. You can use the Pico's GPIO pins 0 and 1 for serial debugging. The caveat is that these pins are normally address bits 0 and 1, so if you enable serial debugging these two address bits will be forced to 0.

ISA to Pico Pinout

This table shows the mapping between the ISA bus pins and the Pico's GPIOs.

ISA	GPIO	Pin
A00	GP00	01
A01	GP01	02
A02	GP02	04
A03	GP03	05
A04	GP04	06
A05	GP05	07
A06	GP06	09
A07	GP07	10
A08	GP08	11
A09	GP09	12
A10	GP10	14
A11	GP11	15
IRQ	GP12	16
MEMR-	GP13	17
MEMW-	GP14	19
DB0	GP15	20
DB1	GP16	21
DB2	GP17	22
DB3	GP18	24
DB4	GP19	25
DB5	GP20	26
DB6	GP21	27
DB7	GP22	29
IOR-	GP26	31
IOW-	GP27	32
IO_RDY	GP28	34

Since the default configuration is using COM4's I/O Address and IRQ, here is a reminder of the serial port addresses and IRQs.

COM	I/O Addr	IRQ
COM1	0x3F8	4
COM2	0x2F8	3
COM3	0x3E8	4
COM4	0x2E8	3