Questions about the distance measurement mesh model

[AndyM]

Hello

My application is based on the Distance measurement sample which uses a BLE  scan response callback to trigger the measurement synchronization sequence in reflector mode and scan callback to trigger synchronization sequence in  initiator mode. With the Distance mesh model the measurement sequence is started with the bt_mesh_dm_cli_measurement_start API

It seems that simply calling this API every time a scan packet arrives is going to overwhelm the mesh network. On the other hand it would be great to receive more than one measurement so averaging can be applied. What's your recommendation on how frequently should  bt_mesh_dm_cli_measurement_start API be called?
Also

There is an API bt_mesh_dm_cli_results_get() which returns the measurement results.

However the results are available in the bt_mesh_dm_cli_measurement_start() callback. 
Can you clarify when this function should be called?
Do you plan to add a sample how the DM model should be used? That would very helpful

Thank you

Andy

[AndyM]

One other  thing
There are 2 API's in the DM library 

nrf_dm_calc() and 

nrf_dm_high_precision_calc()
It would be great to  have a parameter to  control which one is used

[AHaug]

Hi,

I will ask the Mesh developers about your questions and if we've planned a sample, so I'll get back to you when I hear from them

Kind regards,
Andreas

[AndyM]

AHaug said:

node cannot participate in the mesh communication during DM ranging. 

Can you clarify - does this apply to the ranging or synchronization phase or both?
In my experiments it can take 1-10 seconds to receive the measurement result. Farther nodes tend to take longer to measure

[AHaug]

Hi,

I've noted that you're also interested in a sample, but unfortunately the same reply with regards timeline will go here as well. I will let you know if and when I get it done.

Kind regards,
Andreas

[AHaug]

Hi,

AndyM said:

Can you clarify - does this apply to the ranging or synchronization phase or both?

This will be during both phases. 10 seconds sounds like a long time to receive the measurement results. I will clarify this number with the Mesh team and ask them if the results sounds within expectations

Kind regards,
Andreas

[AndyM]

Andreas

I'm still stuck with my effort to incorporate the DM mesh model into my application and need help there. I added both client and server models to my  mesh model composition but cannot even use the mesh DM shell sample to start a measurement - it returns an error. There is an entry above with the details but I can provide more if that's not enough. Thank you

[AHaug]

Hi,

I'm waiting for some input from the Mesh developers. Hopefully I hear back from them next week.

Apologies for the inconvinience,

Kind regards,
Andreas

[AndyM]

Update

Got it to work, Can use mesh dm in the shell and measure distance between 2 nodes

Here is what I had to do i

1. proj.conf 

CONFIG_BT_MESH_DM_CLI=y

CONFIG_BT_MESH_DM_SRV=y

2. Add dm server and client to model composition

struct bt_mesh_model _vnd_models[] = {

   // your vendor models

    // Distance measurement models.

    BT_MESH_MODEL_DM_CLI(&_dm_client),

    BT_MESH_MODEL_DM_SRV(&_dm_srv)

};

// config client.used for provisioning via shell

struct bt_mesh_cfg_cli       _config_client;

static struct bt_mesh_model _root_models[] = {

    BT_MESH_MODEL_CFG_SRV,          

    BT_MESH_MODEL_CFG_CLI(&_config_client),

};

static struct bt_mesh_elem _elements[] = {

    BT_MESH_ELEM(0, _root_models, _vnd_models),

};

3. I use mesh shell to provision. Added the following commands 

bind dm client model to node address

mesh models cfg model app-bind <node addr> 0 0x000C 0x0059

bind dm server model to node address

mesh models cfg model app-bind <node addr> 0 0x000B 0x0059

NOTE

0x0059 is Nordic BLE ID. Must bind these models using Nordic ID not your company ID 

Otherwise bind fails

Provisioned 2 nodes

Now can do the following in the mesh shell

mesh init

mesh target dst <node address>

mesh models dm start 1 (MPCD mode) <other node addr>
Get this back 

Status: Success (err: 0)

Entry number: 1
Mode: MCPD
Quality: 0
Error Occurred: 0
Address: 0X0001
Best distance (cm): 60
IFFT distance (cm): 60
Phase slope distance (cm): 196
RSSI open space distance (cm): 891

NOTE

The measurement takes about 2 seconds ( 1 minute 51-52 seconds) 

This is for 2 devices within BLE range

Seems  a bit long