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Bluetooth-Devices / bthome-ble

Parser for BTHome BLE devices
https://bthome.io/
MIT License
64 stars 11 forks source link

timestamp sensor 32-bit? year 2038 overflow? #85

Closed scottcopus closed 11 months ago

scottcopus commented 11 months ago

Sorry, I'm new to BTHome and just want to make sure the timestamp is futureproofed.

Is the timestamp sensor a 32-bit or 48-bit number? https://bthome.io/format/ says "uint48 (4 bytes)" which seems ambiguous, unless I'm misunderstanding the info.

If it's only 32-bit, then it'll overflow in 2038! https://en.wikipedia.org/wiki/Year_2038_problem

BTW, it might be a good idea to add webpage #anchors to all BTHome.io webpages that have multiple/long sections to them so it's easy for someone to deep-link.

Ernst79 commented 11 months ago

It’s 4 bytes, excl. the byte for the sensor type. I see I made an error in the table, the example should be 0x50 5d396164, so 4 bytes (unsigned) following 0x50 for timestamp. I have updated the example.

With 0x50 ffffffff We get 4294967295 as integer, which is Sunday 7 February 2106 06:28:15 in epoch time as maximum date. So, no 2035 bug, but a 2108 bug, but I assume we can live with that.

scottcopus commented 11 months ago

Ah, I didn’t recognize that timestamp was also unsigned which helps it last a bit longer. ;) If this is acceptable by other devs in the general HA world, I’m good with it.

Ernst79 commented 11 months ago

By the time we get close to 2108 I’ll add a 5 byte long timestamp, if I still live. Help me remember by that time 😄