bgl-read

Note

This is based on the Sensotrend/sensotrend-uploader.

I just needed to be able to read data from a Contour Next One (older USB model) to grab the BGL data for someone else.

Claude did all the hard yards figuring out how to convert the small portion I needed into Rust.

Overview

Reads blood glucose readings from a Bayer/Ascensia Contour Next USB meter and outputs them as JSON or CSV.

Tested against the Contour Next One (USB model). Other Contour Next variants that use the same ASTM-over-HID protocol should also work — see docs/devices/contour-next.md for protocol details.

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Building

cargo build --release

The binary ends up at target/release/bgl-read.

On macOS you may need to grant input-device access the first time you run it; the OS will prompt you.

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Running

Plug the meter in via USB, then:

# JSON (default) — device info + all readings
bgl-read

# CSV
bgl-read --format csv

# Show a live progress line while reading
bgl-read --progress

# Write to a file instead of stdout
bgl-read --format csv --output readings.csv

# List connected Contour devices
bgl-read --list

Output formats

--format	Description
json	Device info and readings as pretty-printed JSON
csv	One reading per row, header included
records	Raw ASTM record text as received from the meter (useful for debugging)
bytes	Hex dump of every HID packet exchanged (TX and RX)

Timestamps are in the meter's own local time (no timezone attached — the device has no concept of timezone).

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Supported devices

All Contour Next devices share USB vendor ID 0x1A79 (Ascensia / Bayer).

Product ID	Device
0x7800	Contour Next One (USB-only variant)
0x7440	Contour Next USB
0x7350	Contour Next
0x7900	Ascensia Contour Next
0x6220	Contour Next Link
0x6230	Contour Next Link 2.4

The tool opens the first matching device it finds. Run --list to see what is connected.

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Notes

• The meter stores the 800 most recent readings in a circular buffer — older readings are silently overwritten. Read regularly if you need a complete history.
• Control solution readings (used to verify the meter) are detected via the annotation field and excluded from output.
• --format records output is the raw meter transcript: the header (H) line includes the meter's password and serial number, and the dump contains every reading. Redact these before sharing dumps publicly (e.g. when filing issues).