Thursday, December 4, 2014

RAW Libre Data Update

Quick update on the Freestyle Libre raw data format.

I have made some progress in my investigations and have developed a couple of utilities. The screenshots below should be self-explanatory to developers. I will not, for the moment, post a detailed how-to. If you can't make sense of what is shown below, please wait.

Here's what happens after a read - the wrap around table of immediate values is updated. The <<now>> pointer indicates the value that will be updated next.

As a sanity check, here is what has happened after 18 minutes. The table of wrap around values has been completely updated and the pointer for the next immediate value is now 2 records ahead. (18=16+2). The table of historical values has also been updated (with a somewhat funky looking value this time). In general, the behavior is quite consistent, but I have interrupted transmissions from time to time and other quirks, mostly due to the fact that it is a bit hard to scan the back of your arm with a large phone NFC sensor that needs to be quite close and stable relatively to the sensor to get accurate or uninterrupted reads.

I have a couple of ideas about that data itself, but they aren't ripe enough to be posted publicly yet. Stay tuned.

Note: I really, really like the Libre. If Abbott could market it more widely and as a full featured CGM, I would definitely buy one. Meanwhile, given the uncertainty, I might simply build one for my private use.

Note 2: this blog is made in ... which means that I can't typically have a quick meeting in DC or San Diego ;-)

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