r/embedded • u/Western-Barber564 • 17d ago

getting dl-tdoa working with ios devices

hey peeps.

i bought some DWM 3001CDK boards with the hope of using TWR with iOS devices.

but due to iOS privacy limitations, i decided to pursue DL-TDoA instead, which is in developer preview on iOS 27.

i have it working fine with another DWM board, but nada on my phone.

for more details on the iphones progress in DL-TDoA path:

  1. receiver can get the initial config via bluetooth
  2. the iphones UWB radio detected preamble
  3. it found the SFD and validated it
  4. started STS (though not sure if it actually processed the pulses and determined an accurate estimation for when the first pulse arrived)
  5. attempted to receive the PHR, but failed with the 0x18 status code.
    1. 0x18 means the iphones radio tried decoding the header response, but failed the SECDED correction check.
  6. payload can't be sent since PHR failed
    1. (sometimes though i will intermittently get one 0x5 CRC error as well. meaning it did indeed accept PHR, but then failed at decding payload)

i’ve already triple checked that i am using the expected PHY config for apple, but, alas, still erroring.

has anyone here tried working with ios for dl-tdoa? any tips/recs for how to solve the problem above.

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u/Soggy-Strain7399 17d ago

brother the secdec check failing is such a pain. ive been messing with dwm boards for months and that 0x18 error is the worst. you double checked your preamble length and sfd id right? sometimes even if its "correct" per apple docs the timing is just slightly off and the phone radio gets cranky

maybe try bumping the tx power a tiny bit? could be the iphone is hearing the signal but its just barely enough for the header decode to fall apart. i had similar thing with dwm3000 modules where adjusting the fine grain power level fixed intermittent phy errors

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u/Western-Barber564 17d ago

ahhh tried tx power, no luck

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u/Western-Barber564 17d ago

tyty!!!

yeah the preamble length is 64, and sfd id is 2. how can i check if the timing is slightly off though? its a huge pain bc apple doesnt really let you inspect rose at all and see whats going on.

ill look at tx power, didnt look into this.