Repairing TI-83 Plus Displays

Sometime last year I scored a cheap TI-83 Plus Silver Edition (SE) on Ebay, however the seller discovered before shipping that it had some display problems- there would sometimes be vertical blank lines on the display or it might not display anything at all. They were going to cancel the sale because it wasn’t in complete working condition as originally claimed, but being familiar with the hardware for these calculators and their common issues, I was happy to buy it anyway under the assumption that I could fix it myself. This turned out to be true, and in the interest of assisting others who have similar problems with calculators, I am herein describing the process involved in making those repairs.

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Monitoring (and preventing) excessive hard drive head parking on Linux

It is fairly well-known among techies that hard drives used in server-like workloads can suffer from poor configuration by default such that they frequently load and unload their heads, which can cause disks to fail much faster than they otherwise would. While I have been aware of this in my home server as well, it is easy to forget to ensure that disks are not silently killing themselves by cycling the heads. Since I use Prometheus to capture information on the server’s operation however, I can use that to monitor that my hard drives are doing well. Collecting SMART metrics The Prometheus Node Exporter is the canonical tool for capturing machine metrics like utilization and hardware information with Prometheus, but it alone does not support probing SMART data from storage drives.

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Cross-compiling CMake projects for Windows

I sometimes find myself wanting to cross-compile programs with CMake on a Linux machine such that I get a standalone .exe that can be given to mostly non-technical Windows users to run. This isn’t hard, but finding the right options is a little bit of a challenge every time, so now I’m recording the procedure here; both as a reminder to myself, and to provide a quick recipe that future searchers can use. Cross-compiling for Windows will of course need an appropriate toolchain, which these days tends to be mingw-w64. Many Linux distributions provide packages for it: mingw-w64 on Debian (including Ubuntu and variants), mingw-w64-gcc on Arch and similar for other distributions.

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Windows MIME type detection pitfalls

I’ve been doing some Django development lately, and was mystified why it seemed the debug toolbar on my local development instance wasn’t showing up, though it had been in the past. It turns out to have been a surprising interaction between browsers sometimes enforcing that resources be served with correct MIME types and the way Windows provides system-wide MIME type configuration (which seems to have major flaws)!

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tihle: a unique TI calculator emulator

Today I’m publishing tihle, a new emulator targeting TI graphing calculators (currently only the 83+, but maybe others later). There’s rather a lot to say about it, but here I will discuss the motivation for a new emulator and the state of the art followed by technical notes on the design and initial development process.

tihle running Phoenix
Yes, it runs Phoenix!

Read on for that discussion, or jump straight to the project homepage on GitLab which has a live demo that runs in your web browser and other resources including source code.

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A Wayback Machine Bookmarklet

Sometimes I find it useful to be able to quickly save a page to the Wayback Machine, often to be able to provide a stable link to a page that I don’t control- for instance if I’m pointing somebody to a document that describes something they’re asking about, then it’s nice to ensure that there will still be an archived copy if the original goes away. While the landing page on web.archive.org has a “save now” form to quickly save a page given its URL, this is still more cumbersome than I’d like- it involves copying the desired URL, opening a new tab to web.

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Fomu: a beginner's guide

FPGAs are pretty cool pieces of hardware for tinkering with, and have become remarkably easy to approach as a hobbyist in recent years. Boards like the TinyFPGA BX don’t require any special hardware to use and can provide a simple platform for modestly-scoped projects or just for learning.

While historically the software tools for programming FPGAs are proprietary and provided by the hardware manufacturer, Symbiflow (enabled and probably inspired by earlier work like Project IceStorm) provides completely free and open-source tooling and documentation for programming some FPGAs, significantly lowering the cost of entry (most vendors provide some free version of their design software but limited to lower-end devices; a license for the non-free version of the software is well into the realm of “if you have to ask, you can’t afford it”) and appearing to yield better results in many cases.1


As somebody who finds it fun to learn new things and experiment with new kinds of creations, FPGAs are quite interesting to me- they’re quite complex devices that enable very powerful creations, with excellent depth for mastery. While I did some course lab work with Altera FPGAs in university (and a little bit of chip design/layout later), I’d call those mostly canned tasks with easily-understood requirements and problem-solving approaches; it was sufficient to familiarize myself with the systems, but not enough to be particularly useful.

The announcement of Fomu caught my interest because I was aware of the earlier Tomu but wasn’t sufficiently interested to try to acquire any hardware. With Fomu however, I’m rather more interested because it enables interesting capabilities for playing with hardware- others have already demonstrated small RISC-V CPUs running in that FPGA (despite its modest logic capacity), for instance.

Even more conveniently for being able to play with Fomu, I’ve been in contact with Mithro who is approximately half of the team behind Fomu and gotten access to a stockpile of “hacker edition” boards that have been hand-assembled but not programmed at all. With slightly early access to hardware, I’ve been able to do some exploration and re-familiarize myself with the world of digital logic design and figure out the hardware.

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Temperature Logging: Redux

Previously as I was experimenting with logging the temperature using a Raspberry Pi (to monitor the temperatures experienced by fermenting cider), I noted that the Pi was something of a terrible hack, and it should be possible to do more efficiently with some slightly less common hardware.

I decided that improved version would be interesting to build for use at home, since it’s both kind of fun to collect data like that, and actually knowing the temperature in the house is useful at times. The end result of this project is that I can generate graphs like the one below of conditions around the house:

Three graphs of temperature, barometric presure and humidity spanning a week, where each graph has three lines; one each for the lounge, bedroom and entry. Temperature shows a diurnal cycle with mostly constant offsets between lines, presure is equal for each and varies slowly over the entire week, and humidity is broadly similar between the three lines and varies somewhat more randomly.

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Building a terrible 'IoT' temperature logger

I had approximately the following exchange with a co-worker a few days ago:

Them: “Hey, do you have a spare Raspberry Pi lying around?”
Me: [thinks] “..yes, actually.”
T: “Do you want to build a temperature logger with Prometheus and a DS18B20+?
M: “Uh, okay?”

It later turned out that that co-worker had been enlisted by yet another individual to provide a temperature logger for their project of brewing cider, to monitor the temperature during fermentation. Since I had all the hardware at hand (to wit, a Raspberry Pi 2 that I wasn’t using for anything and temperature sensors provided by the above co-worker), I threw something together. It also turned out that the deadline was quite short (brewing began just two days after this initial exchange), but I made it work in time.

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