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I didn't reverse-engineer the protocol for my blood pressure monitor in 24 hours

349 points by jamesbelchamber

by jvanderbot

2 subcomments

Buried deep is this gem:
```
    I tried feeding a lot of this into various Als (Kagi gives you access to a few with a nice interface) and I found that they mostly were stupid in ways that made me think.
```
Perfect summary of why AI is useful for rubber ducking. Doing this with a co-worker you always get some questions that are a few layers too shallow for what you need (because they haven't been thinking about it more than a few minutes), but it always makes you think and really helps.

by cestith

14 subcomments

Regarding white coat hypertension, the shot isn’t always necessary. Some people’s blood pressure just goes up from the stress of the clinical setting.

by devinvs

1 subcomments

my best shot at it:

  year:   bits 0-6 reversed
  month:  bits 6-10 reversed
  hour:   bits 13-18
  minute: bits 18-24
  day:    bits 24-29 (maybe reversed)

unsatisfyingly I don't have any idea what the gaps are or why parts need to be reversed, so i could be wrong. With the data from the post:

  y  mo d  h  mi
  25 11 10 11 3
  25 11 10 11 31
  25 11 10 12 1
  25 11 10 12 35
  25 11 10 13 0
  25 11 10 13 31
  25 11 10 13 31
  25 11 10 14 0

by alina_3339

3 subcomments

I’ve been wearing a heart rate monitor for a while, and after analysing the data, I noticed something interesting: my heart rate spikes in only two situations, when I’m driving, and when I’m talking to my wife.

by broken-kebab

0 subcomment

"I'm pretty sure that reverse-engineering this will be good for my blood pressure."
I feel healthier after reading this.

by lifeisstillgood

4 subcomments

So I did something similar (well less cool), but as old Software devs start finding our bodies don’t work as well after a while we will see more and more of this sort of “taking control”
https://mikado-aktiia.readthedocs.io/en/latest/

by pinkmuffinere

2 subcomments

> I tried feeding a lot of this into various Als (Kagi gives you access to a few with a nice interface) and I found that they mostly were stupid in ways that made me think
"stupid in ways that made me think" is (IMO) a really good summary of how AI is useful, as well as its pitfalls.

by hermitcrab

2 subcomments

I am having issues with hypertension and purchased one of these:
https://hilo.com
You put on a cuff (supplied) to calibrate it, and then you wear a little gadget on your wrist. It takes frequent measurements throughout the day and night when it senses you aren't moving. It then syncs with your phone to store the results. Its a little pricey, but seems to work well[1]. And it avoids the faff of a pressure cuff[2] and 'white coat hypertension'.
[1] Apart from the option on the app to do a reading from your finger using your phone camera - which gives wildly different results to a cuff.
[2] You need to recalibrate it every month or so using the cuff.

by Arch-TK

1 subcomments

Would be fun to see the traffic dumps, I would love to try to figure out the protocol offline with them.
Just spent half a day reverse engineering a Windows virtual printer driver (for work) and had to force myself to stop spending the rest of the day doing it.

by nullbyte808

3 subcomments

Orange juice and bannas. My BP was 142/90 and is now 125/80. Eating these twice a day nets you nearly 2000 MG potassium.

by supportengineer

4 subcomments

Not a single comment in here about Bottles - what exactly is it?

by ndsipa_pomu

1 subcomments

I enjoyed the writing style (maybe it's the mistrust of Windows).
I'm currently wearing a cheap smart-watch (<£20) that I spotted on AliExpress (i.e. Chinese product) that unbelievably records biometrics such as blood pressure and blood lipid profiles. I was mainly curious about the uric acid measurements as I get the occasional attack of gout, but am curious as to whether it actually does measure anything like blood pressure. I've previously compared the blood glucose measurements by getting my diabetic brother (type 1) to wear it and compare it to a pinprick measurement - within 10% which is pretty much useless for medical usage.

by deevus

1 subcomments

The reason Bottles/WINE doesn't work with USB devices like that is likely because WINE isn't supposed to support kernel level device access. It's for running programs and just fakes enough for that to work.

by khannn

0 subcomment

"Turns out that when you check someone's blood pressure after giving them an injection, it's higher than normal."
Nick-Cage-You-Dont-Say.png

by KeplerBoy

0 subcomment

I guess having a look at the binary with ghidra would make this a lot easier.

by ck2

4 subcomments

I have three blood pressure cuffs
They all give me different numbers, by a lot sometimes
btw you think they ever clean those devices?
you think healthy people go to pharmacies?
I won't even touch the signature pen, imagine what's on that

by jcc11

0 subcomment

Played around with the format a bit and made a Kaitai format if anybody else wants to play with it. Not confident about the year, but I have observed some timestamps based on date of manufacture if the device came out approximately 2016. The rest seems to line up rather well as bit-packed integers.

Kaitai Structured Output:

  0 [BpMsg]: 2025-11-10 11:03 - SYS:137, DIA:113, OPP:121, MAP:121, PP:24, HR:67
      unk1 = 0xA = 10
      sys = 0x89 = 137
      dia = 0x71 = 113
      hr = 0x43 = 67
      timestamp [Datetime]: 2025-11-10 11:03
          yearMinus2016 = 0x9 = 9
          month = 0xB = 11
          day = 0xA = 10
          hour = 0xB = 11
          min = 0x3 = 3
          paddedDay = 10
          paddedHour = 11
          paddedMin = 03
          paddedMonth = 11
          year = 2025
      unk2 = 0x50 = 80
      opp = 0x79 = 121
      unk3 = 0x0 = 0
      unk4 = 0x0 = 0
      unk5 = 0x0 = 0
      unk6 = 0x0 = 0
      unk7 = 0x0 = 0
      unk8 = 0x0 = 0
      map = 0x79 = 121
      pp = 0x18 = 24
  1 [BpMsg]: 2025-11-10 11:31 - SYS:132, DIA:86, OPP:95, MAP:101, PP:46, HR:68
  2 [BpMsg]: 2025-11-10 12:01 - SYS:126, DIA:84, OPP:90, MAP:98, PP:42, HR:82
  3 [BpMsg]: 2025-11-10 12:35 - SYS:128, DIA:80, OPP:86, MAP:96, PP:48, HR:61

KSY:

  meta:
    id: bp
    title: BP Msg Format
    endian: le
  seq:
    - id: msgs
      type: bp_msg
      repeat: eos
  types:
    datetime:
      -webide-representation: '{year:dec}-{padded_month}-{padded_day} {padded_hour}:{padded_min}'
      seq:
        - id: year_minus_2016
          type: b4
        - id: month
          type: b4
        - id: day
          type: b5
        - id: hour
          type: b5
        - id: min
          type: b6
      instances:
        padded_day:
          value: '(day <= 9 ? "0" : "") + day.to_s'
        padded_month:
          value: '(month <= 9 ? "0" : "") + month.to_s'
        padded_min:
          value: '(min <= 9 ? "0" : "") + min.to_s'
        padded_hour:
          value: '(hour <= 9 ? "0" : "") + hour.to_s'
        year:
          value: (year_minus_2016 + 2016).to_s
    bp_msg:
      -webide-representation: '{timestamp} - SYS:{sys:dec}, DIA:{dia:dec}, OPP:{opp:dec}, MAP:{map:dec}, PP:{pp:dec}, HR:{hr:dec}'
      seq:
        - id: unk1
          type: u1
        - id: sys
          type: u1
        - id: dia
          type: u1
        - id: hr
          type: u1
        - id: timestamp
          type: datetime
        - id: unk2
          type: u1
        - id: opp
          type: u1
        - id: unk3
          type: u1
        - id: unk4
          type: u1
        - id: unk5
          type: u1
        - id: unk6
          type: u1
        - id: unk7
          type: u1
        - id: unk8
          type: u1
      instances:
        pp:
          value: sys - dia
        map:
          value: (2 * dia + sys) / 3

Using the following hex dump as my source "binary":

  0a89 7143 9b52 c350 7900 0000 0000 0000  ..qC.R.Py.......
  8456 449b 52df 505f 0000 0000 0000 007e  .VD.R.P_.......~
  5452 9b53 0150 5a00 0000 0000 000a 8050  TR.S.PZ........P
  3d9b 5323 5056 0000 0000 0000 0094 5d41  =.S#PV........]A
  9b53 4050 6700 0000 0000 0000 795c 4a9b  .S@Pg.......y\J.
  535e 506a 0000 0000 0000 007b 5341 9b53  S^Pj.......{SA.S
  5f50 5a00 0000 0000 0000 7b4f 4e9b 5381  _PZ.......{ON.S.
  5058 0000 0000 0000                      PX......

by jesuswasjew

3 subcomments

What's flu vaccine?

by Arainach

1 subcomments

Testing blood pressure after a shot seems weird.
I have high blood pressure, managed with a low dose of medication. I've had plenty of advice from my PCP and other actual doctors on how to take blood pressure - how to sit, how long to sit still, how to position your arm, etc.
It is remarkable how many medically-adjacent professionals are bad at this. My dentist starts my sessions with a blood pressure reading - theoretically in case they have to numb me or something, probably because it's billable or whatever. What always seems to happen is that I get in for my appointment (driving, which can be stressful even if I'm not running late), they take me to the chair within 2 minutes max, immediately put some sort of wrist cuff on me, hold my arm at an angle that is not what most actual doctors have recommended to me and take a reading that is often high enough to surprise both the hygenist and myself.
The thing is that I have two sufficiently-calibrated Omron units, one at home and one at the office. I take my blood pressure often enough to know what it usually is (and my real doctor takes it at least twice a year). That is to say that no, it's not 200/160 or whatever nonsense the dentist thinks it is and you'd think that with a very small amount of reading they'd know better.