Re: Bluetooth mesh - node with 2 elements - Not enough tailroom for TransMIC

Johan Hedberg

Hi Jehudi,

On Tue, Oct 17, 2017, Laczen JMS wrote:
I am trying to make a bluetooth mesh zephyr node with 2 elements.
After provisioning (which assigns 2 node adresses) meshctl ask for the
composition data. This fails with Not enough tailroom for TransMIC:

[bt] [DBG] dev_comp_data_get: (0x20001950) net_idx 0x0000 app_idx 0xfffe src 0x0
[bt] [ERR] bt_mesh_model_send: Not enough tailroom for TransMIC

What configuration option do I need to change (I am working on nrf51822) ?
I think you need to change CONFIG_BT_MESH_TX_SEG_COUNT. IIRC it defaults
to 3, and with your two elements you've created a composition data that
doesn't fit in three segments anymore. Increasing the SEG_COUNT to 4
will probably fix the issue. Note that this will also increase the
runtime memory consumption, so hopefully that doesn't go over your
limits (IIRC you had 16k?).


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