dwm1001 BCNx, SVCx and TWR slot x occpy time

Wireless Connectivity Ultra-Wideband
1

hi, all:

dwm1001 BCNx, SVCx and TWR slot x , how assign their time?

16 BCNx
2 SVCx
15 TWR slots

so 100ms/(16+2+15) = 3ms ?

2

TWR slot is 5ms, others 1ms, 7ms reserved maybe

3

The BCN slots are 500 us, service the same.
TWR slot = 10 x 500 us.

So the BCNs 8 ms, SVC 1ms, 15 TWR slots is 75ms and 16 ms reserved (e.g. used during OTA FW update).

4

hi, zoran:

thanks, why twr slot = 10*500us ? which place describe the information

5

The TWR slot: tag sends a “group poll” message, 4 anchors reply with “poll” messages, tag sends a “response” and 4 anchors reply with “final” messages. 1 + 4 + 1 + 4 = 10 messages = 10 slots. the slots are 500 us as that is the minimum time needed to send a frame and then for the nRF to process it (read the received message, prepare the response etc.) and be ready to send or receive in time for the next slot.

6

yeah, anchors receive group poll. all anchors don’t send the poll message at the same time, so they will send in proper sequence for no collistion.

7

Hi everyone,

I’m don’t know how to get system tick count to calculate the slot of super frame. Anyone else can show me the way, please!
I use xTaskGetTickCount() to get system tick count, but it return tick count in ms. The Super Frame duration is 100ms and slot duration is 500us. Then I can’t calculate exactly slot number.

I’m using decawave example source code at link below https://github.com/Decawave/dwm1001-examples

Thank in advance !

Best regard,
GiauN.