Bus Pirate

From ArchWiki

The Bus Pirate is a versatile tool for communicating with various hardware.

Interfacing a new microchip can be a hassle. Breadboarding a circuit, writing code, hauling out the programmer, or maybe even prototyping a PCB. We never seem to get it right on the first try.

The Bus Pirate is a universal bus interface that talks to most chips from a PC serial terminal, eliminating a ton of early prototyping effort when working with new or unknown chips. Many serial protocols are supported at 0–5.5 volts, more can be added.

Installation

Note: All scripts will assume the device is named /dev/buspirate.

The drivers for the FTDI chip is included in the kernel, so it should be detected as soon as it is plugged in, and assigned to device /dev/ttyUSB[0-9]. To check where it got assigned, run: 

# journalctl -k

The output will contain a line that looks something like this: 

# usb 1-4.4: FTDI USB Serial Device converter now attached to ttyUSB0

udev

It can be annoying to have to look up what /dev/ttyUSB[0-9] the device gets assigned, so it is a good idea to add a simple udev rule that creates the symlink '/dev/buspirate -> /dev/ttyUSB* when it is plugged in.

To figure out the current path to the bus pirate you can use the udevadm(8) monitor command and then plugging in the device the output should be some thing like this: 

$ udevadm monitor --environment --udev 
DEVICENAME=/dev/ttyUSB0
DRIVER=tty
PRODUCT=403/6001/600

After you have plugged et in and the output is given press ctrl+c to break the text stream.

Note: The above results is the only relevant data the rest was discarded to reduce the clutter.

Product/Vendor ID

There are several ways to do this, the way I personally prefer is to use it by vender/product ID so the bus pirate can be replaced without needing to modify the line. To use this method, add the following line to /etc/udev/rules.d/98-buspirate 

/etc/udev/rules.d/98-buspirate.rules
# Bus pirate v3
SUBSYSTEM=="tty", ATTRS{idVendor}=="0403", ATTRS{idProduct}=="6001", GROUP="users", MODE="0666", SYMLINK+="buspirate"
# Bus pirate v4
SUBSYSTEM=="tty", ATTRS{idVendor}=="04d8", ATTRS{idProduct}=="fb00", GROUP="users", MODE="0666", SYMLINK+="buspirate"

Serial number

You can also do it by serial number, to do this, you will need to find out the serial number of FTDI chip on the bus pirate. This can be achieved by running the following, assuming your device is plugged in and was assigned to /dev/ttyUSB0: 

# udevadm info --attribute-walk -n /dev/ttyUSB0  | sed -n '/FTDI/,/serial/p'

Now add/create the following udev rule: 

/etc/udev/rules.d/98-buspirate.rules
SUBSYSTEM=="tty", ATTRS{serial}=="XXXXXXXX", GROUP="users", MODE="0660", SYMLINK+="buspirate"

Change ATTRS{serial}=="XXXXXXXX" to the serial on your device and load the new rule. At this point, whenever you plug in the device, the symlink should be created.

To verify that, run the udev monitor command mentioned above and it should report some thing like this: 

DEVLINKS=/dev/buspirate

Communication

To communicate with the device, you can use any of the following, to name a few:

  • minicom
# minicom -b 115200 -8 -D /dev/buspirate
  • screen
# screen /dev/buspirate 115200 8N1
  • picocom
# picocom -b 115200 /dev/buspirate
  • cu from the uucp package
# cu -l /dev/buspirate

Type '?' and press enter and the device should reply with a list of possible commands.