Light control server: Potential bug when turning off

RE: Light control server: Potential bug when turning off

tesc — Wed, 18 Feb 2026 15:30:42 GMT

Hi,

I am sorry for the delay from my end as well. I do not find the Mesh Model Specification to be the easiest document to understand.

Now, if you have a look at figures 6.6 and 6.7, as well as read section 6.2.5.1 Light LC State Machine states, I think you will find that the Off state is for disabling the controller, while the state set when receiving an OnOff messages is Fade Standby Manual. The timing value for the Lightness Out state then becomes Light LC Lightness Standby - Timer / Transition Time * (Light LC Lightness Standby – Initial Lightness).

In other words, when receiving an OnOff message, the light should not immediately turn off, but rather fade according to certain timer settings. There might of course be more to it, but as far as I can tell our implementation seems to show the correct behavior according to the Mesh Model specification.

Regards,
Terje

RE: Light control server: Potential bug when turning off

Chris_Dev — Sat, 14 Feb 2026 03:26:14 GMT

Good day.

Thank you for getting back to me.

1. We have a proprietary solution which consists of a frontend and backend which communicates with a mesh device to send data out over the air. Essentially, we use the messages provided by NCS client models:

Setting LC properties - bt_mesh_light_ctrl_cli_prop_set()

Setting controller coefficients is a bit different, for that we use - bt_mesh_light_ctrl_cli_coeff_set

LC On/Off set message (so that you don't turn off the controller when turning the light on and off) - bt_mesh_light_ctrl_cli_light_onoff_set

2. Well it depends on what lux values you receive from your sensor node... Sometimes it takes up to 5 minutes (without real lux values i.e. the sensor is not observing the true lux, it's just place somewhere random).....

In any event, I am expecting to see the light turn off immediately if you send a Light on/off = OFF message. According to the specification..... It does not matter what your run/prolong/standby values are. Also, this should not be dependent on the PI control loop, according to my understanding at least. Instead of the light turning off immediately, the controller regulates down to 0 eventually.

Hope this helps?

Apologies for taking so long to reply.

Regards

RE: Light control server: Potential bug when turning off

tesc — Wed, 04 Feb 2026 15:20:12 GMT

Hi,

I do have a couple of questions, for clarity:

1. What device/app/other are you using for configuring and sending messages to the LC device, and what messages are you sending (or what exactly are you doing in the interface of the app etc.)
2. Can you quantify the time taken for the light to turn off and on? (I.e. number of seconds, instead of "very long time".) Preferably also what time you expect, in addition to what time you observe, for both turning off and on.

Regards,
Terje