glucometerutils news: many more meters, easier usage and Windows support

You probably have noticed by now that I write about glucometers quite a bit, not only reviewing them as an user, but also reverse engineering to figure out their protocols. This all started four years ago when I needed to send my glucometer readings to my doctor and I ended up having to write my own tool.

That tool started almost as a joke, particularly given I wrote it in Python, which at the time I was not an expert in at all (I have since learnt a lot more about it, and at work I got to be more of an expert than I’d ever expected to be). But I always known that it would be for the most part just a proof of concept. Not only exporting CSV is mostly useless, but the most important part in diabetes management software is the analysis and I don’t have any clue how to do analysis.

At first I thought I could reuse some of the implementation to expand Xavier’s OpenGlucose but it turned out that it’s not really easy for those meters that are using serial adapters or other USB devices beside the HID ones that he implemented already. Of course this does mean it would probably work fine for things like the FreeStyle Libre which I appear to have written the only Linux software to download from, but even in that case, things are more complicated.

Indeed, as I have noted here and there previously, we need a better format to export glucometer data, and in particular the data from continuous or mixed meters like the Libre. My current out format for it only includes the raw glucose readings from the meter that are not marked as errors; it does provide an unstructured text comment that tells you whether the reading is coming from the background sensor, an explicit scan or a blood sample, but it does not provide all the level of details of the original readings. And it does not expose ketone readings at all, despite the fact that most of the FreeStyle-line devices support them and I even documented how to get them. But this is a topic for a different post, I think.

On the other hand, over the past four years, the number of meters increased significantly, and I even have a few more that I only have partially reversed and not published yet. Currently there are 9 drivers, covering over a dozen meters (some meters share the same driver, either because they are just rebranded versions or simply because they share the same protocol). One is for the InsuLinx, which also loses a bunch of details, and is based off Xavier’s own reverse engineering — I did that mostly because all the modern FreeStyle devices appear to share the same basic protocol, and so writing new drivers for them is actually fairly trivial.

This would make the project an interesting base if someone feels like writing a proper UI for it. If I ever tried to look into that, I may end up just starting an HTTP server and provide everything over HMTL for the browser to render. After all that’s actually how OpenGlucose is doing things, except there is no server, and the browser is embedded. Alternatively one could just write an HTML report file out, the same way Accu-Chek Mobile does using data URLs and JavaScript bundles.

One of the most important usability changes I have added recently, though, is allowing the user not to specify the device path. When I started writing the tool, I started by looking at serial adapter based devices, which usually come with their own cable, and you just access it. The next driver was for the LBA-over-SCSI used int he OneTouch Verio, which I could have auto-detected but didn’t, and the following ones, mostly based off HID, I just expected to be given an hidraw path.

But all of this is difficult, and indeed I had more than a few people asking me which device are they meant to use, so over the past few months I adapter the drivers to try auto-detecting the devices. For the serial port based meters, the auto-detection targets the original manufacturer’s cable, so if you have a custom one, you should still pass them a path. For HID based devices, you also need the Python hidapi library because I couldn’t bother writing my own HID bus parsing on Linux…

… and the library also brings another important feature: it works on non-Linux operating systems. Indeed I now have not one but two confirmed users that managed to use the tool on Windows, for two separate FreeStyle devices (at the time of writing, the only ones implementing HID-based protocols, although I have another one in the pipeline.

Supposedly, all of this should work fine on macOS (I almost called it OS X), though the one person who contacted me trying to have it working there has been having trouble with it — I think the problem has something to do with the Python version available (I’m targetting Python 3 because I had a very hard time to do the right processing with Python 2.7). So if you want to give it a try feel free.

And yes, I’m very happy to receive pull request, so if you want to implement that HTML output I talked above about, you’re awesome and I’m looking forward to your pull request. I’m afraid I won’t be much help with the visualisation though.

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