[Matthew “wrongbaud” Alt] is well known around these parts for his hardware hacking and reverse-engineering lessons, and today he’s bringing us a JTAG hacking primer that demoes some cool new hardware — the PiFEX (Pi Interface Explorer). Ever wondered about those testpoint arrays on mSATA and M.2 SSDs? This write-up lays bare the secrets of such an SSD, using a Pi 4, PiFEX, OpenOCD and a good few open-source tools for JTAG probing that you can easily use yourself.
The PiFEX hat gives you level-shifted bidirectional GPIO connectors for UART, SPI, I2C, JTAG, SWD and potentially way more, an OLED screen to show any debugging information you might need, and even a logic analyzer header so that you can check up on your reverse-engineering progress.
The suggested software workflow pulls no punches either, proposing ease-of-use features like USB-Ethernet gadget mode and Jupyter notebooks. [wrongbaud] shows us how to find JTAG among the dozen testpads left on the SSD, get the SSD single-stepping through code, and dump some of its memory space as a test. Full of tricks of the trade like reverse-engineering devices on a sheet of paper you can leave markings on, this write-up gives you a solid background in JTAG hacking, even if you only have a Pi and an old SSD.
So how can you get your hands on one? [wrongbaud] says the plan is to open source both the PiFEX hardware and software in the near future. Until until then, it looks like at least the hardware it wouldn’t be too hard to re-implement it yourself if you wanted to get the hang of reverse ..
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