Multi-byte data using Mesh Sensor Model

[abumbalough21]

Hello,

I am trying to adapt the new Mesh Sensor Model examples in v4.2.0 of the SDK for Mesh to allow sending >1 byte sensor data over the mesh network. I have two nRF52840DK boards, with one running the sensor server example and the other running the sensor client example. I have been able to successfully use the stock example code to transmit 1 byte of data from server to client. 

I tried modifying the code to send 4 data bytes by modifying the sensor server example file "main.c". I first modified the code on line 192 from

required_out_bytes = 1;

  to

required_out_bytes = 4;

Then I replaced lines 225-227 with the following lines:

p_out[0] = 0x00; p_out[1] = 0xC0; p_out[2] = 0xFF; p_out[3] = 0xEE;
*p_out_bytes = 4;

The modified code builds with no errors, but when I press RTT key 8 on the client side to send the status GET message for the Motion Sensed property I receive the following error in the server RTT terminal:

<t:     175638>, main.c,  240, inadequate buffer (0x0042 (66), 4, 1) = (property id, required, actual)
<t:     175645>, app_sensor_utils.c,  705, ERR: sensor_get_cb() failed (1, 0) = (bytes expected, bytes returned).
<t:     175649>, app_error_weak.c,  105, Mesh assert at 0x00028512 (:0)

Upon further inspection, it seems the line that throws this error comes from the file "app_sensor_utils.c" inside the "sensor_current_value_set(sensor_cadence_t * p)" function.

if (bytes != p->range_value_bytes_allocated)
    {
        __LOG(LOG_SRC_APP, LOG_LEVEL_ERROR,
              "ERR: sensor_get_cb() failed (%d, %d) = (bytes expected, bytes returned).\n",
              p->range_value_bytes_allocated,
              bytes);

        NRF_MESH_ASSERT(false);
    }

I have attempted to work back from this point to find where the "range_value_bytes_allocated" value is set, but I have not been able to find it.

I appreciate any and all assistance you can provide me in resolving this issue!

[Didrik Rokhaug]

Hi.

Unfortunately, our Mesh experts are on vacation at the moment, but I'll do my best to help in the meantime.

range_value_bytes_allocated is set to range_vector_bytes, one of the arguments in the cadence_initialize function in app_sensor_utils.c:519.

cadence_initialize is called in two different functions:

cadence_new and sensor_cadence_create.

In cadence_new, range_vector_bytes is set by the cadence_bytes_get function, which in turns calls range_vector_bytes_get. In range_vector_bytes_get, we find that range_vector_bytes is set to sizeof(pir_data_size_t). pir_data_size_t is defined in app_sensor.h as a uint8_t.

If we track the flow through sensor_cadence_create instead, we find the same path through cadence_bytes_get.

Searching through the sample for pir_data_size_t reveals that it is only used in two places, and both places are only using the size of the type. No variable of the type pir_data_size_t is ever created. The two places the size of pir_data_size_t is used is in range_vector_bytes_get (app_sensor_utils.c:79) and delta_vector_bytes_get (app_sensor_utils.c:93).

I hope that helps you getting further.

Best regards,

Didrik

[abumbalough21]

Hi Didrik,

Thanks so much for your help! I've been working through this all morning and actually just reached the same conclusion that you provided me here. I'm now working on modifying the app_sensor_utils.c file to accommodate the request for a 4 byte data value.

[Jianan]

Hi there,

I have the same issue as yours, I am curious that whether you have solved this issue or not. I appreaciate your help!

Thanks 

[osti]

Hi,

Did you solve the problem? I would be interested in that too.

I would be grateful for your help.

Thanks.

[Jianan]

Hi osti,

I kinda of solve that, I can send maximum of 8 byte data value for now. 

In app_sensor_utils.c, use n*sizeof(pir_data_size_t) where n is the number of byte you use. 

In main.c, under the app_sensor_get_cb, change required_out_byte = n on the ID you want to modified. 

That's the modification I done. FYI 8 is the maximum number can transfer data without any delay. Let me know if you have any question. Also, if you can get more than 8 bytes please let me know. 

Good luck

Jianan

[osti]

Hi Jianan,

Thanks so much for your help! 

I get all data. 

Best regards

Christopher

[ccasebeer]

Thanks so much for this.

I too was able to enlarge my data to uint16_t. Going to try float here in a bit.

I followed your code snippets and they worked.