tdoa distance diff error

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justinleeyang
Expert
Posts: 171
Joined: Mon Dec 28, 2015 5:07 am

tdoa distance diff error

Post by justinleeyang » Sat Mar 24, 2018 10:41 am

hi,

tdoa anchor mode:

Code: Select all

#define NSLOTS 8
#define TDMA_SLOT_BITS 26 // 26: 2ms timeslot
#define TDMA_NSLOT_BITS 3
about the distance difference between anchors, the right value should be ~0.3m, get many wrong value as follow:

314852.0000
314756.0000
......
358941.0000

then adjust the TDMA_SLOT_BITS to 27, the wrong value reduce, but occurs once Occasionally.

why?

arnaud
Bitcraze
Posts: 1939
Joined: Tue Feb 06, 2007 12:36 pm

Re: tdoa distance diff error

Post by arnaud » Mon Mar 26, 2018 9:56 am

Do you get spikes, intermittent bad values, or is it consistently wrong?

Guglie
Beginner
Posts: 7
Joined: Mon Mar 26, 2018 5:23 pm

Re: tdoa distance diff error

Post by Guglie » Mon Mar 26, 2018 5:29 pm

Very interesting, I'm also trying to get better results from TDOA, what are the TDMA_SLOT_BITS?

justinleeyang
Expert
Posts: 171
Joined: Mon Dec 28, 2015 5:07 am

Re: tdoa distance diff error

Post by justinleeyang » Tue Mar 27, 2018 2:45 am

hi, arnaud:

when TDMA_SLOT_BITS set as 26, consistently wrong;
then set as 27, intermittent bad values.

arnaud
Bitcraze
Posts: 1939
Joined: Tue Feb 06, 2007 12:36 pm

Re: tdoa distance diff error

Post by arnaud » Wed Mar 28, 2018 7:45 am

Hum, this looks like packet collision. Are you using un-modified firmware or have you changed anything. I am thinking about radio settings that could change the packet timing.

justinleeyang
Expert
Posts: 171
Joined: Mon Dec 28, 2015 5:07 am

Re: tdoa distance diff error

Post by justinleeyang » Wed Apr 04, 2018 12:08 pm

yes, I open other tag or anchor, they send ~30 packets per second, so affect my tdoa anchors and tag receive result in distance diff error.

arnaud
Bitcraze
Posts: 1939
Joined: Tue Feb 06, 2007 12:36 pm

Re: tdoa distance diff error

Post by arnaud » Fri Apr 06, 2018 6:08 am

What version of the node firmware are you using (what git commit)?

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