DISCLAIMER: THIS WORK REPRESENTS A CLEAN ROOM DESIGN OF THE DATA FROM THE YUWELL YH550 CPAP/APAP MACHINE
Extract charts like this
WARNING: This is very much a work-in-progress, but it does produce usable charts from sleep data.
DISCLAIMER: THIS SHOULD NOT BE USED FOR ANY DIAGNOSTIC PURPOSES
This parses and presents data from a DJMed/Yuwell CPAP/APAP machine. These machines store data on SD Card in session files ending with the .bys extension.
This is a binary grammar. The 010 editor grammar support file is included in the doc directory.
I am still figuring out the binary grammar, particularly the flags in each record, which could be any of the following:
- CSR = Cheyne-Stokes Respiration, heart disease related breathing
- LL = Large Leak (Leaks Lpm information is found in the record structure)
- CA = Central Apnea (found)
- OA = Obstructive Apnea (found)
- H = Hypopnea (found)
- UA = Unknown Apnea
- RE = RERA = Respiratory Effort Related Arousal
Any information about these flags and locations would be very welcome.
As this project stands, the data can be used to product meaningful charts of daily usage.
Yuwell do provide software for this unit called BreathCare Station. It is a Windows application. You could probably try to get it working in Wine maybe or whatever the equivalent is on MacOS. This is here to provide some insight into the machine and how things are stored. There are open source CPAP applications like OSCAR which could integrate this data. I believe there is also Home Assitant plugins for some CPAP so that you can control air conditioners and such like based on events. Hopefully this information can help someone.
Right now, this will show charts for all files found in the data directory of the repo. This uses uv for package management. But it only uses matplotlib and numpy for the charts.
This was developed using Python 3.14, but it should work in 3.7+. Without the charts, there are no other dependencies on top of Python 3.7+. Just a couple of dataclasses.
- Clone this repository
- Install the dependencies with either
uv syncorpip install matplotlib numpy - Copy your
.bysfiles into thedatadirectory directly, no sub-directories - Run
python main.py
I've found these as re-branded units from many companies and drop-shipping establishments. The base manufacturer is Yuwell and this model appears to be a YH550.
The file consists of two main sections:
- File header
- Log records
The file header contains fixed length fields and is 51 bytes in length. It includes machine settings and a summary of the logs. Most numeric fields are unsigned bytes.
Dates are formatted with a single byte for year, month, day, hour, minute and seconds.
Years are 2 digit (25=2025 etc.)
Decimal values are represented as the value multiplied by 10
File is little endian
| Offset | Length | Data |
|---|---|---|
| 0 | 6 | Log start date/time |
| 6 | 6 | Log end date/time |
| 12 | 1 | Mode: 0x00=CPAP, 0x01=APAP |
| 13 | 1 | Ramp up time (minutes, integer) |
| 14 | 1 | Initial pressure (Decimal) |
| 15 | 1 | Minimum pressure (Decimal) |
| 16 | 1 | Maximum pressure (Decimal) |
| 17 | 1 | unknown |
| 18 | 1 | Humidity setting (integer) |
| 19 | 7 | unknown |
| 26 | 1 | Average leak volume (Decimal) |
| 27 | 1 | unknown |
| 28 | 1 | Average pressure (Decimal) |
| 29 | 1 | unknown |
| 30 | 16 | Product serial number |
| 46 | 2 | Record count |
| 48 | 2 | unknown (possibly related to record count) |
| 50 | 1 | Header end marker (0xF9) |
Each record represents a minute of data containing the pressure level and leak level as well as event flags, most of which are currently not known. Each record is 10 bytes in length.
According to the documentation, the file could contain SPo2 and pulse data. Which could be the fields with no data as my unit does not measure either.
| Offset | Length | Data |
|---|---|---|
| 0 | 1 | Pressure cmH2O (Decimal) |
| 1 | 1 | unknown (No data) |
| 2 | 1 | unknown (No data) |
| 3 | 1 | oai (Values seen are 0, 1) |
| 4 | 1 | hi (Values seen are 0, 1, 2) |
| 5 | 1 | cai (Values seen are 0, 1, 2) |
| 6 | 1 | unknown (Values seen are 0, 1) |
| 7 | 1 | unknown (No data) |
| 8 | 1 | unknown (No data) |
| 9 | 1 | Leak volume Lpm (Decimal) |
NOTE: The user manuals for the Yuwell units are included, there are no copyright terms in either documents.
From what I understand, some Yuwell CPAP/APAP machines do provide the following:
- SPo2 data
- Pulse data
It could be possible that this grammar includes this.
The binary grammar coverage currently stands at ~81%
There are several bytes in this dataset which currently have no identified data:
With data
- Bytes 49 and 50 of the header record, which appear to be closely related to the record count in bytes 47 and 48, usually off by one
- Byte 7 of the log record, values seen are
[0, 1]indicating some kind of event although I've not observed matching events in the Breathcare station software
Without data
- Header bytes 18, 20, 28 and 30
- Log record bytes 2, 3, 8 and 9
I have only observed zeroes in these bytes.