only two tags range at the same time with TDMA

Firmware/software/electronics/mechanics
justinleeyang
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Joined: Mon Dec 28, 2015 5:07 am

Re: only two tags range at the same time with TDMA

Post by justinleeyang »

hi,

a issue, 26 means 480 slots, but how to calculate it?
I see the comment about "since the timer is running at ~64GHZ".
arnaud
Bitcraze
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Joined: Tue Feb 06, 2007 12:36 pm

Re: only two tags range at the same time with TDMA

Post by arnaud »

In theory you would calculate the frame frequency with 64GHz / 2^(n+m):
- n the number of bit per slot
- m the number of bit to encode the slot ID (2^m slot per frame).

And the slot frequency with 64GHz / 2^n.

The bug here is that 64e9 / 2^26 = 953Hz, the double! I have a +1 in most of these time calculation I think this is the source of the bug. 27 should have been the correct value.

By the way, is it working properly at 480Hz slot rate?
justinleeyang
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Posts: 186
Joined: Mon Dec 28, 2015 5:07 am

Re: only two tags range at the same time with TDMA

Post by justinleeyang »

hi, arnaud:

thanks your reply! I have understanded your method, 480 slots no problem, and I will add more tag to test.
arnaud
Bitcraze
Posts: 2538
Joined: Tue Feb 06, 2007 12:36 pm

Re: only two tags range at the same time with TDMA

Post by arnaud »

Thanks for testing! I will test as well and fix the implementation.

We are having a demo at Maker Faire Berlin at the end of the week and it is really nice to find that now: we only have 2x2m to fly autonomously and having twice as much ranging will certainly help!
justinleeyang
Expert
Posts: 186
Joined: Mon Dec 28, 2015 5:07 am

Re: only two tags range at the same time with TDMA

Post by justinleeyang »

Good luck for you, and wish that I will join the Maker Faire next year.
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