Nordic Distance Measurement library - dm_report not being populated

[mkopp]

I have successfully managed to incorporate the hard-float build of the library for the nrf52840 into my bare-metal application (custom hardware with an nrf52840) and have been able to get successful rangings (dm_status=NRF_DM_STATUS_SUCCESS) between 2 nodes, one acting as a reflector and the other as an initiator. However the nrf_dm_report_t doesnt get populated except for some values. Every now and then a ranging is unsuccessful, but all successful ones show the same as below. As I cannot dig deeper into the nrf_dm implementation, I was wondering if you could provide me with some insight on what could be going on.

Here is the serial log with the contents of dm_report:

[DM][000000010] I: NRF DM library version: nrf_dm_0.7.5+
[DM][000000011] I: nrf_dm_config_t:
[DM][000000011] I: Role: 1
[DM][000000011] I: Ranging Mode: 1
[DM][000000011] I: RNG Seed: 4294967295
[DM][000000011] I: TX Power (dBm): 4
[DM][000000011] I: Antenna Composition: 0
[DM][000000014] I: I Tones Local: 0, 0, ..., 0
[DM][000000014] I: Q Tones Local: 0, 0, ..., 0
[DM][000000014] I: I Tones Remote: 0, 0, ..., 0
[DM][000000014] I: Q Tones Remote: 0, 0, ..., 0
[DM][000000019] I: SINR Indicators: 0
[DM][000000019] I: Ranging Mode: 1
[DM][000000019] I: Distance Estimates: IFFT: , Phase Slope: , RSSI Openspace: , Best:
[DM][000000025] I: Status: 0
[DM][000000025] I: Link Loss: 42
[DM][000000025] I: RSSI Local: 38
[DM][000000025] I: RSSI Remote: 38
[DM][000000025] I: TX Power Local: 4
[DM][000000025] I: TX Power Remote: 4
[DM][000000025] I: Quality: 0
[DM][000000025] I: RTT Accumulated (ns): 0
[DM][000000025] I: RTT Count: 0
[DM][000000031] I: nrf_status: 0

Here is the code excerpt:

dm_status = nrf_dm_proc_execute(timeout_us);
if (dm_status == NRF_DM_STATUS_SUCCESS)
{
    nrf_dm_populate_report(&dm_report);
    quality = nrf_dm_calc(&dm_report);
    duration = nrf_dm_get_duration_us(&dm_config);
    distance = nrf_dm_high_precision_calc(&dm_report);
    nrf_dm_get_hopping_sequence(&dm_config,hopping_seq);
    dm_print_report(&dm_report);
}

Thank you for your assistance, let me know if you need more details.

BR Mickael

[Hung Bui]

Hi Mickael, 
Håkon is on vacation this week so I will take over in the mean time. 

mkopp said:

- does the dm library assume I have the BT stack implemented / do I need to have the nrf softdevice flashed? (I assume it justs needs to control the radio peripheral)

As far as I know the dm library is independent from the RF protocol you use. So it doesn't require BT stack. You can find the info here:
https://docs.nordicsemi.com/bundle/ncs-latest/page/nrf/libraries/others/dm.html

I will need to get people with deeper knowledge on nrf_dm to help on your other questions. As mentioned by Håkon, we have limited support for using the library in bare metal. Please let us know the result when you test with the DKs. 

[mkopp]

Hello, thank you for your reply.

I finally was able to get back to the project this morning and tested it with 2 DKs: same result.

After some further investigation I have found the culprit. A little embarrassing but the logging module I was using does not have an implementation for printing floats, hence the empty values in the first post. Converting the results before printing solved the issue. I wish I had thought of this earlier. It indeed has been working since the first try...

Thank you for trying to solve a problem that didnt exist!

Best regards,

Mickael