BT785 - Revision history

Bertrik Sikken: /* bluetooth advertisement data */

2025-12-24T16:53:11Z

bluetooth advertisement data

← Older revision		Revision as of 16:53, 24 December 2025
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	=== bluetooth advertisement data ===		=== bluetooth advertisement data ===
	Advertisement manufacturer data:		Advertisement manufacturer data:
	* item ~~2000~~ = 00 00 0100 449b6a4ea8ea8d8ecddb794250608546		* item 0x7D0 (TuYa company id) = 00 00 0100 449b6a4ea8ea8d8ecddb794250608546
	This can be decoded as, see https://github.com/PlusPlus-ua/ha_tuya_ble/blob/main/custom_components/tuya_ble/tuya_ble/tuya_ble.py#L308		This can be decoded as, see https://github.com/PlusPlus-ua/ha_tuya_ble/blob/main/custom_components/tuya_ble/tuya_ble/tuya_ble.py#L308
	* [0] = 0 -> is_bound = false		* [0] = 0 -> is_bound = false

Bertrik Sikken: /* Hardware */

2025-11-01T11:59:40Z

Hardware

← Older revision		Revision as of 11:59, 1 November 2025
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	* about 40mm inner diameter		* about 40mm inner diameter
	* Looks like EAN 8716936051895, possibly finer pitch		* Looks like EAN 8716936051895, possibly finer pitch
			* Looks like https://www.bol.com/nl/nl/p/afsluitkap-binnendraad-en-rubber-ring-1/9200000047473976

	== Analysis ==		== Analysis ==

Bertrik Sikken: /* Hardware */

2025-11-01T07:42:42Z

Hardware

← Older revision		Revision as of 07:42, 1 November 2025
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	Cap specifications:		Cap specifications:
	* about 40mm inner diameter		* about 40mm inner diameter
	* Looks like EAN 8716936051895		* Looks like EAN 8716936051895, possibly finer pitch

	== Analysis ==		== Analysis ==

Bertrik Sikken: /* Hardware */

2025-11-01T07:41:20Z

Hardware

← Older revision		Revision as of 07:41, 1 November 2025
Line 29:		Line 29:
	Cap specifications:		Cap specifications:
	* about 40mm inner diameter		* about 40mm inner diameter
	* ~~...???~~		* Looks like EAN 8716936051895

	== Analysis ==		== Analysis ==

Bertrik Sikken: /* Hardware */

2025-10-26T09:00:27Z

Hardware

← Older revision		Revision as of 09:00, 26 October 2025
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	Perhaps we can 3d-print a replacement cap, put a permanent 5V power cable through it, so it is not reliant on primary batteries anymore.		Perhaps we can 3d-print a replacement cap, put a permanent 5V power cable through it, so it is not reliant on primary batteries anymore.

			Cap specifications:
			* about 40mm inner diameter
			* ...???

	== Analysis ==		== Analysis ==

Bertrik Sikken: /* Layering */

2025-10-20T06:59:59Z

Layering

← Older revision		Revision as of 06:59, 20 October 2025
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	** 2-byte length L		** 2-byte length L
	** L-byte payload, this is command specific data		** L-byte payload, this is command specific data
	** 2-byte CRC		** 2-byte CRC, over all earlier bytes in the frame
	* <b>Commands/responses/data point data</b>, in the case of a measurement report, these have the following encoding:		* <b>Commands/responses/data point data</b>, in the case of a measurement report, these have the following encoding:
	** 1-byte DP id, e.g. 8 = temperature for BT785		** 1-byte DP id, e.g. 8 = temperature for BT785

Bertrik Sikken: /* Protocol */

2025-10-20T06:58:44Z

Protocol

← Older revision		Revision as of 06:58, 20 October 2025
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	* <b>Framing layer</b>, splits large packets up into smaller fragments, to work around MTU limitations:		* <b>Framing layer</b>, splits large packets up into smaller fragments, to work around MTU limitations:
	** packets are segmented into 20-byte units, each prefixed by a header that contains packet number, length byte and encrypted payload		** packets are segmented into 20-byte units, each prefixed by a header that contains packet number, length byte and encrypted payload
			** the length byte is coded as a varint (7 bit value + continuation bit)
	* <b>Encrypted payload layer</b>, encrypts data using AES		* <b>Encrypted payload layer</b>, encrypts data using AES
	** data is padded to 16-byte units		** data is padded to 16-byte units

Bertrik Sikken: /* BT875 data points */

2025-10-20T06:57:43Z

BT875 data points

← Older revision		Revision as of 06:57, 20 October 2025
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	\|}		\|}

	Measurement data is reported using code 0x8006, ~~typically~~ one item per bluetooth message.		Measurement data is reported using code 0x8006, one item per bluetooth message.
	The DP is prefixed with 00f00000008000		The DP is prefixed with 00f00000008000

Bertrik Sikken: /* BT875 data points */

2025-10-19T18:49:45Z

BT875 data points

← Older revision		Revision as of 18:49, 19 October 2025
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	\| 08 \|\| 02 (INT) \|\| 4 \|\| Temperature (0.1 deg C)		\| 08 \|\| 02 (INT) \|\| 4 \|\| Temperature (0.1 deg C)
	\|-		\|-
	\| 65 \|\| 00 (raw) \|\| 9 \|\| unknown, seen 010001010101000000		\| 65 \|\| 00 (raw) \|\| 9 \|\| unknown, seen 010001010101000000, could be alarm flags?
	\|-		\|-
	\| 6A \|\| 02 (INT) \|\| 4 \|\| Temperature (0.1 deg F)		\| 6A \|\| 02 (INT) \|\| 4 \|\| Temperature (0.1 deg F)

Bertrik Sikken: /* Layering */

2025-10-19T18:49:12Z

Layering

← Older revision		Revision as of 18:49, 19 October 2025
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	** data is padded to 16-byte units		** data is padded to 16-byte units
	** prefixed with a 1-byte key type (04 or 05), a 16-byte initial vector, data is encrypted with AES in CBC mode		** prefixed with a 1-byte key type (04 or 05), a 16-byte initial vector, data is encrypted with AES in CBC mode
	* <b>Command/response ~~packets~~</b>, within each ~~packet~~:		* <b>Command/response frames</b>, within each frame:
	** 4-byte sequence number of the sender side, each side keeps its own sequence number		** 4-byte sequence number of the sender side, each side keeps its own sequence number
	** 4-byte sequence number of the related packet (in a response, the sequence number of the command packet), or 0 if not applicable		** 4-byte sequence number of the related packet (in a response, the sequence number of the command packet), or 0 if not applicable
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	** L-byte payload, this is command specific data		** L-byte payload, this is command specific data
	** 2-byte CRC		** 2-byte CRC
	* <b>~~Data~~ point data</b>, in the case of a measurement report, these have the following encoding:		* <b>Commands/responses/data point data</b>, in the case of a measurement report, these have the following encoding:
	** 1-byte DP id, e.g. 8 = temperature for BT785		** 1-byte DP id, e.g. 8 = temperature for BT785
	** 1-byte DP type (0 = raw, 1 = boolean, 2 = int, 3 = string, 4 = enum)		** 1-byte DP type (0 = raw, 1 = boolean, 2 = int, 3 = string, 4 = enum)