Implement SET_NUTRITION packet

[hertzg]

I do not have enough samples to understands this packet.

Having enough samples showing:

• Diffenret fields populated with different values in app
• Bytes sent to and from the BLE service

would (probably) help understand:

• How float values are coded
• Which fields are transfered vs computed
• How are they coded in the packet.

It would be great if someone can provide that information using an Android phone (I no longer have one).

This can be done using adb and wireshark if anyone is willing to provide samples I can write up a guide how to do it.

[wilsonsilva]

I'm willing to help. I would like to see this protocol completely reverse engineered. Today I'll start an open-source clone of the mobile app, to own the data and fix the sync with Fitbit that has plagued the app for years.

[hertzg]

Thats great, if you can provide wireshark pcaps of set nutrition packets while you take note of what values you wrote into the fields might help understand the packet. 👍

[hertzg]

Apparently the nutrition payload is super simple 🤦‍♂️

feefc0a2c2240f423e0f423e [01869e 01869e 01869e 01869e 01869e 01869e 01869e 01869e 01869e 01869e] 76

Payload

bytes (incl.)	field	unit	values
[0, 2]	calories	Kcal (5)	0x0 - 0xf423f 0.0 - 99999.9
[3, 5]	caloriesFromFat	Kcal (5)	0x0 - 0xf423f 0.0 - 99999.9
[6, 8]	totalFat	g (4)	0x0 - 0x1869e 0.0 - 9999.9
[9, 11]	stauratedFat	g (4)	0x0 - 0x1869e 0.0 - 9999.9
[12, 14]	transFat	g (4)	0x0 - 0x1869e 0.0 - 9999.9
[15, 17]	cholesterol	mg (4)	0x0 - 0x1869e 0.0 - 9999.9
[18, 20]	sodium	mg (4)	0x0 - 0x1869e 0.0 - 9999.9
[21, 23]	potassium	mg (4)	0x0 - 0x1869e 0.0 - 9999.9
[24, 26]	totalCarbs	g (4)	0x0 - 0x1869e 0.0 - 9999.9
[27, 29]	dietaryFiber	g (4)	0x0 - 0x1869e 0.0 - 9999.9
[30, 33]	sugars	g (4)	0x0 - 0x1869e 0.0 - 9999.9
[34, 36]	protein	g (4)	0x0 - 0x1869e 0.0 - 9999.9

This also tends to auto reset to 0 ONLY when the measurement hits 0.