Kai Gossner's I3C Blaster Turns a Raspberry Pi Pico Into a Handy USB to I3C Bridge

If you're looking to play with MIPI's successor to I2C on a tight budget, the I3C Blaster is for you.

Gareth Halfacree
22 days agoDebugging / HW101

Kai Gossner has released a tool for anyone looking to experiment with the I3C bus on a budget, turning a Raspberry Pi Pico or compatible microcontroller board into a USB to I3C bridge — just throw on the firmware and add a couple of resistors to get started.

"I3C Blaster is a firmware image you can flash to your Raspberry Pi Pico board to let it act as USB to I3C converter," Gossner explains of the project. "Simply add two pullup resistors and you are ready to go. Why did I develop I3C Blaster? Because so far there is no easy and low [cost] solution available to learn [the] I3C protocol or evaluate I3C target devices in the market. Having the ability to execute I3C transfers was for me also a major step in understanding the I3C protocol and its many exceptions and hidden features and the reasons behind them."

The I3C bus, also known as SenseWire, was launched by the MIPI Alliance in 2016 with a view to improving upon the classic I2C bus — hence its full name, Improved Inter-Integrated Circuit. WHile it allows for limited backwards compatibility with I2C, the I3C bus brings its own improvements including considerably higher throughputs — but the high cost of I3C hardware compared to I2C means that it's not often seen in-the-wild at the hobbyist level.

I3C Blaster looks to change all that: installed on a Raspberry Pi Pico or other RP2040-based microcontroller board, the firmware enables it to act as a USB to I3C bridge — complete with an interactive console accessible over a serial port. The project also delivers the ability to run automated testing — delivering what Gossner calls "an autoidentification scheme" for finding which serial port the I3C Blaster is using at the time of a test.

Gossner is also working on a voltage level-shifter for use with a Seeed XIAO RP2040 microcontroller board, with a Raspberry Pi Pico version planned as a follow-up to the release of the firmware itself. "The board will support 1.2V to 3.3V (nominal) IO [Input/Output] voltages and has a special mechanism implemented to boost edges," the maker writes. "The market does right now not have level translators with edge shaping available which cover also higher voltages of 3.3V."

The I3C firmware is available on GitHub, under the permissive MIT license. "Use at your own risk," Gossner warns. "I am not guilty for any negative effect like broken hardware or data loss."

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire: freelance@halfacree.co.uk.
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