Nordic Distance Measurements

[franck]

Hello, 

How much time takes the Nordic Distance Measurements in MCPD mode with IFFT on nrf52832 ?

Any limitaion on moving objects except that this measurement works well on short distance ?

Thanks 

Franck

 

[Simonr]

Hi Franck

What time exactly are you looking for? The minimum time between timeslots are by default set to 8ms (8000µs) with the CONFIG_DM_MIN_TIME_BETWEEN_TIMESLOTS_US. This time should also account for processing of ranging data after the timeslots. You can also define the time between the synchronization and ranging (request) with CONFIG_DM_RANGING_OFFSET_US .

Increasing this allows more ranging to different nodes, but increases latency. Regarding movement, I think the limitation or offset would be however long you move it in 8ms (time between events).

Best regards,
Simon

[franck]

Hello Simon,

Thanks for your answer. My concern that current distance measure report between 2 devices is only 2 or 3 values per seconds I would need more. Consumption is not an issue. As which device are reflector and initiator are defined as well as BT device address. Is this possible to call continuously dm_request_add on both devices everytime a timeout or a sucess result is returned ??

What are other solution to increase the number of distance measure reported per seconds ??

Thanks

[Simonr]

Hi FrancK

franck said:

current distance measure report between 2 devices is only 2 or 3 values per seconds I would need more.

How many reports would you need per second?

The Kconfig options CONFIG_DM_TIMESLOT_QUEUE_COUNT_SAME_PEER and CONFIG_DM_TIMESLOT_QUEUE_LENGTH define how many measurements are scheduled. The more measurements are scheduled, the more of them take place, which increases power consumption but gives more frequent rangings. At the application runtime, the additional delay of measurement execution is configured using the start_delay_us parameter of the dm_request structure. This option helps in adjusting the synchronization. The CONFIG_DM_INITIATOR_DELAY_US Kconfig option defines the initiator delay. Increasing the values of these parameters increases the latency and power consumption.

Best regards,

Simon

[franck]

Hello Simon,

Thanks for your answer, I would need at least 10 values per seconds, and even more would be even better like 20 or so

Will try the tuning of the parameters

Also, power consumption is really not important for my device 

Franck

[franck]

I played with values but did not seem to improve a lot, managed to get 4-5/secs, not sure I understood fully the parameters how to change the settings

Could you share a Kconfig file that should increase the rate 

Thanks a lot