Comment by solarkraft

Ha, I've soldered to the same pins as the author! I just left the wires dangling out of the case, but pulled them through the aluminum latches (?) in the case for some stabilization.

> Final hurdle: the kindle serial port runs at 1.8v, so I needed a serial port adaptor which supports that

It turns out that most adapters support receiving at 1.8V, you just need a simple voltage divider to keep them from sending more.

Unfortunately I didn't really achieve what I wanted to - I'd like to wake the Kindle using some external device that can poll data at lower power (Thread/BLR/ESP Now) to build an E-Ink display with a long battery life and that can be updated with a relatively low latency. It seems like the chip has a feature for being woken up from deep sleep via UART, but it's disabled by default and needs to be set with a kernel parameter and I haven't managed to set one so far (cmdline set in U-Boot keeps being reset to the original one). Maybe someone has an idea? Does my approach even make sense? Could I get away with a similar efficiency with the Kindle's hardware alone?

... if you want most other things, you don't really even need to open the shell, though. There's a huge amount of software-based jailbreaks over on Mobileread along with cool helpful software tools, tips and cool people. The Kindle is a whole single board computer with a full Linux system (which is a joy to explore by the way, it's largely made up of shell scripts and js, which is often not only not obfuscated, but commented! big components used include upstart, X11, GTK2 and awesome) and you can install fairly modern software on it - though the kernel (2.6 or so) and architecture (armhf) is starting to limit the older versions a lot. Still, I have Python 3.7 (I think) and Syncthing on my Kindle Touch and it's working quite well.

One use case for actually soldering to the pins is that you can build with it with very little messing around with software. My uncle, a tinkerer without any Linux experienced, is considering just using the Kindle as a dumb display to be drawn to, which this approach would be ideal for. Compute the password, log in, draw using the CLI tools or directly to the framebuffer, all without ever pressing a button on the Kindle.

... these devices are cool. Repurposing old cheap consumer hardware is very cool. Though the Kindle Touch is still very capable for reading (with KOReader, of course)!