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RAPT Thermometer data structure

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Masahiko

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Joined
Mar 31, 2025
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Location
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Hi ,
I am trying to obtain temperature data from RAPT BLE thermometer through BLE communication.
I analyzed BLE advertisement data using wireshark plug-in .
Now I figured out what data is temperature data .
But I am not sure how I can convert these bytes into temperature data in celsius .

If Anyone already done , please help .

Masahiko @ JAPAN
 

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I've tried to find the provolone of RAPT BLE thermometer for a while. Not found anything, yet.
How do you conclude that those two bytes are temperature data?
What was the temperature like for that data?
 
I've tried to find the provolone of RAPT BLE thermometer for a while. Not found anything, yet.
How do you conclude that those two bytes are temperature data?
What was the temperature like for that data?
Hi !
I am so happy to meet the guy who is also trying to do this !
Actually it is not confirmed yet but when I was watching manufacturer data with WireShark . These 2 bytes only changes while a change the
temperature of the probe .
Then I am just GUESSING these 2 bytes is expressing temperature reading .
I tried to calculate these bytes with some of the method I ever known . But there was no luck .
If you have some other method of calculate temperature from 2 bytes data , please share with me .
 
I've tried to find the provolone of RAPT BLE thermometer for a while. Not found anything, yet.
How do you conclude that those two bytes are temperature data?
What was the temperature like for that data?
Hi !
I am so happy to meet the guy who is also trying to do this !
Actually it is not confirmed yet but when I was watching manufacturer data with WireShark . These 2 bytes only changes while a change the
temperature of the probe .
Then I am just GUESSING these 2 bytes is expressing temperature reading .
I tried to calculate these bytes with some of the method I ever known . But there was no luck .
If you have some other method of calculate temperature from 2 bytes data , please share with me .
 
Hi !
I am so happy to meet the guy who is also trying to do this !
Actually it is not confirmed yet but when I was watching manufacturer data with WireShark . These 2 bytes only changes while a change the
temperature of the probe .
Then I am just GUESSING these 2 bytes is expressing temperature reading .
I tried to calculate these bytes with some of the method I ever known . But there was no luck .
If you have some other method of calculate temperature from 2 bytes data , please share with me .
Was the test temperature for the provided data near 50°C ?
 
Here are some thoughts of the possible encodings:

- RAPT Pill's: Divide by 128, subtract 273.15
- BTHome way: multiply by 0.01

0x4a 0xc3 in little endian is 0xc34a= 49994(decimal).
= ~118.43 by Pill's encoding
= 499.94 by BTHome's encoding

More data might be needed.
 
Here are some thoughts of the possible encodings:

- RAPT Pill's: Divide by 128, subtract 273.15
- BTHome way: multiply by 0.01

0x4a 0xc3 in little endian is 0xc34a= 49994(decimal).
= ~118.43 by Pill's encoding
= 499.94 by BTHome's encoding

More data might be needed.
Actually I did both method.
I will do some more research and show you some more data soon.
 
Hi folks ,
It is a puzzle game time !

24.7 C

0000 02 15 4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 ..Keg."1Iw.&%.La
0010 6e 64 4a 76 58 00 00 ndJvX..

29.8 C

0000 02 15 4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 ..Keg."1Iw.&%.La
0010 6e 64 4b b2 58 00 00 ndK.X..


29.2 C

0000 02 15 4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 ..Keg."1Iw.&%.La
0010 6e 64 4b 90 58 00 00 ndK.X..

28.7 C

0000 02 15 4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 ..Keg."1Iw.&%.La
0010 6e 64 4b 6a 58 00 00 ndKjX..

28.2 C

0000 02 15 cb 65 67 b7 22 31 49 6f 85 26 25 b7 4c 61 ...eg."1Io.&%.La
0010 6e 64 4b 56 58 00 00 ndKVX..


80.2 C

0000 02 15 4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 ..Keg."1Iw.&%.La
0010 6e 64 58 38 58 00 00 ndX8X..


80.5 C

0000 02 15 4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 ..Keg."1Iw.&%.La
0010 6e 64 58 6a 58 00 00 ndXjX..


79.8 C

0000 02 15 4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 ..Keg."1Iw.&%.La
0010 6e 64 58 3d 58 00 00 ndX=X..
 
BINGO!!!!

I didn't tried to divide by 64 . I just did with 128 .
I also worked with CHAT-GPT .

Humans are better than AI so far yet !

I am going to purchase another RAPT thermometer to identify which is the serial number field .


Thanks a lot !
 
Well, I checked Tilt's format, which broadcast in Apple's Becaon format. So here it is

4c 00 // Apple iBeacon
02 // ibeacon type
15 // length = 21
4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 6e 64 // 16 byte UUID
4a 76 // major
58 00 // minor
00 // tx power

The temperature is stored in major field.

FYI,
I checked the data of my RAPT thermometer. The UUID is exactly the same as yours, while my minor number is
46 00.

There might not be any serial number. You can get MAC address by the protocol itself.
 
Well, I checked Tilt's format, which broadcast in Apple's Becaon format. So here it is

4c 00 // Apple iBeacon
02 // ibeacon type
15 // length = 21
4b 65 67 b7 22 31 49 77 85 26 25 b7 4c 61 6e 64 // 16 byte UUID
4a 76 // major
58 00 // minor
00 // tx power

The temperature is stored in major field.

FYI,
I checked the data of my RAPT thermometer. The UUID is exactly the same as yours, while my minor number is
46 00.

There might not be any serial number. You can get MAC address by the protocol itself.
We can assume MAC address is unique value for identifying each meters .
As you mentioned , I might not need to search serial number.

What kind of tool do you usually use for monitoring BLE communications ?

I always use nRF52840 sniffer with WireShark.
 
Are you trying to build something specific?
I built mash temp / fermentation tracking software by myself for myself .
I just wanted to add RAPT thermometer to my support thermometer list .
So I don't have to use another thermometer when I am mashing .
My software is still on progressing .
I am soon going to add PH tracking feature while mashing .
 
We can assume MAC address is unique value for identifying each meters .
As you mentioned , I might not need to search serial number.

What kind of tool do you usually use for monitoring BLE communications ?

I always use nRF52840 sniffer with WireShark.
I used an ESP32 with my software, a modified version of BrewPiLess.

I built mash temp / fermentation tracking software by myself for myself .
I just wanted to add RAPT thermometer to my support thermometer list .
So I don't have to use another thermometer when I am mashing .
My software is still on progressing .
I am soon going to add PH tracking feature while mashing .
I am also interested in this feature. However, I don't know where to find a food safe probe that can be used in high temperature.
 
It come to me that maybe minor is the battery level of the device.

So 0x58 = 88 %, while 0x46= 70%.

It is the only information other than temperature.
 
I think he is talking about PH probe .
I can find many 'Food Grade PH sensor ' on the net , but I haven't learned lot about them .
So far , I don't think about 'Immersion sensor' . I think it would be enough to take small samples during mash .
Would you please share some of your list of Good Grade pH sensor?
I am more interested in fermentation pH monitoring, though.
 
Would you please share some of your list of Good Grade pH sensor?
I am more interested in fermentation pH monitoring, though.
I think you can just Google with 'foodgrade PH sensor' . You will see many of food grade PH sensor probes .
Or do I misunderstand what you say ??
ex)
InPro X1 pH sensor
https://www.mt.com/in/en/home/library/white-papers/process-analytics/food-safe-ph-sensor.html
LabSen®751 Food-grade Titanium-body Spear pH Electrode/Probe-Apera Instruments
https://aperainst.com/labsen-751
Unbreakable pH electrode for food industry. | Elscolab
https://elscolab.com/en-nl/blog/unbreakable-cip-resistant-ph-electrode
 
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