Michael Hope
9c4f388977
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55 lines
3.8 KiB
Markdown
55 lines
3.8 KiB
Markdown
---
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title: Ampler eBike Bluetooth protocol
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authors: [michaelh]
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date: 2024-05-12
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---
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I have an [Ampler Stout][stout] eBike which exposes metrics as Bluetooth attributes over [GATT]. I'd
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like to track the battery level and odomoter, so spent some time and decoded some of the attributes.
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The bike exposes:
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| Characteristic | Example data |
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| ------------------------------------ | ------------------------------------------------------------------------------- |
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| 340d1528-a89e-4d4e-9078-06d21096ea36 | 0x5b 0x00 0x00 0x00 0x11 0x02 0x00 0x00 0x04 0x01 0x00 0x00 0x00 0x00 0x00 0x00 |
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| 340d1529-a89e-4d4e-9078-06d21096ea36 | 0x00 0x00 0x00 0x00 0xdf 0x14 0x00 0x00 0x9c 0x0a 0x90 0x00 |
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| 340d1530-a89e-4d4e-9078-06d21096ea36 | 0xa0 0x00 0x90 0x01 0x02 0x00 0x06 0x00 0x64 0x00 0xfa 0x00 |
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| 340d1536-a89e-4d4e-9078-06d21096ea36 | 0x01 |
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| 340d1538-a89e-4d4e-9078-06d21096ea36 | 0x00 |
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| 340d1542-a89e-4d4e-9078-06d21096ea36 | 0x58 0x02 |
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| 340d1544-a89e-4d4e-9078-06d21096ea36 | 0x00 |
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| 340d1545-a89e-4d4e-9078-06d21096ea36 | 0x0a 0x18 0xe2 0x64 |
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| 340d1547-a89e-4d4e-9078-06d21096ea36 | 0xff 0x02 0x11 0x00 0x00 0x00 0x03 0x00 |
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| 340d1548-a89e-4d4e-9078-06d21096ea36 | 0x04 0x00 0x00 0x00 0x00 0x00 0x00 0x00 |
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| 340d1549-a89e-4d4e-9078-06d21096ea36 | 0x00 0x00 0x00 0x00 |
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| 340d1550-a89e-4d4e-9078-06d21096ea36 | 0x33 |
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The format appears to pack related values into the same characteristic. Values are little endian and
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either half words or words. The units seem to be metric such as `m` for range and `m/s` for speed
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with a power of 10 multiplier, such as the voltage being in decivolts:
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| Characteristic | [Format] | Fields |
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| ------------------------------------ | -------- | --------------------------------------------- |
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| 340d1528-a89e-4d4e-9078-06d21096ea36 | HHhH | % charged, voltage (dV), temperature (dºC), ? |
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| 340d1529-a89e-4d4e-9078-06d21096ea36 | III | ?, speed (mm/s), odometer (dm) |
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| 340d1536-a89e-4d4e-9078-06d21096ea36 | B | assist level (0, 1, 2) |
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| 340d1538-a89e-4d4e-9078-06d21096ea36 | ? (bool) | light |
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| 340d1545-a89e-4d4e-9078-06d21096ea36 | I | ? increases over time 1692538885 |
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The time value isn't clear but might be a POSIX time, i.e. roughly Sunday, 20 August 2023.
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Decoding the example above gives:
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| Characteristic | Fields |
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| ------------------------------------ | ------------------------------------- |
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| 340d1528-a89e-4d4e-9078-06d21096ea36 | 91 % charged, 52.9 V, 26.0 ºC, 0 |
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| 340d1529-a89e-4d4e-9078-06d21096ea36 | 0, 5343 mm/s (19.2 km/h), 943.9900 km |
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| 340d1536-a89e-4d4e-9078-06d21096ea36 | assist level 1 |
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| 340d1538-a89e-4d4e-9078-06d21096ea36 | light off |
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Next step is to implement a decoder, export this to Home Assistant, and collect it via Prometheus.
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[format]: https://docs.python.org/3/library/struct.html#format-characters
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[gatt]: https://learn.adafruit.com/introduction-to-bluetooth-low-energy/gatt
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[stout]: https://amplerbikes.com/en-CH/e-bikes/stout
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