Set new channel map

RE: Set new channel map

EthanJia — Wed, 15 Jun 2022 09:27:40 GMT

Hi!

Thanks! I got it. Appreciate it a lot.

Best regards :-)

Ethan

RE: Set new channel map

Sigurd — Wed, 15 Jun 2022 08:13:11 GMT

[quote user="EthanJia"] but there are no default channel monitoring methods running in the background?[/quote]

Correct.

[quote user="EthanJia"]We should integrate the monitoring function into those examples/templates by ourselves. Is that correct?[/quote]

Typically it's the BLE central that implements this. If you are creating a BLE central, then you might want to use the Quality of Service feature to set new channel maps.

RE: Set new channel map

EthanJia — Tue, 14 Jun 2022 16:19:51 GMT

Hi there!

[quote userid="15146" url="~/f/nordic-q-a/61624/set-new-channel-map/251959#251959"]This channel map means that all data channels can be used. It will do frequency hopping, but it will by-default not be adaptive. To be adaptive, you would need to periodically update the channel map based on the measurements of the energy levels on the Bluetooth Low Energy channels. The Quality of service feature for channel monitoring in the SoftDevice can be used for this. See this link , you might find this repo useful.[/quote]

So, according to this, can I understand it in this way, that SoftDevice itself only implements the frequency hopping function, but there are no default channel monitoring methods running in the background?

Further speaking, all of the examples/templates in nRF5 SDK and SoftDevice do not perform channel monitoring. We should integrate the monitoring function into those examples/templates by ourselves. Is that correct?

Really appreciate it if this could be helped ASAP.

Best regards :-)

Ethan

RE: Set new channel map

dmitry_t — Thu, 04 Jun 2020 05:59:00 GMT

Hi!

Thank you for the clarification.

I'm currently working on more priority task, so I'll back to this and check channel map settings later on.

Regards,

Dmitry.

RE: Set new channel map

Sigurd — Wed, 27 May 2020 12:50:40 GMT

Hi,

[quote user=""]1. Is that true if I want to use specific BLE channels I need to do it just once on a central device?[/quote]

Yes, from the documentation here, we have that "When setting the channel map, it applies to all current and future connections".

[quote user=""]2. Is that true once channel map is set it will be used for all next connections until it's changed again?[/quote]

Yes, see 1.

[quote user=""]3. Is that true it's not necessary to set channel map only when connection event happens? I can do it, say, when I initialize central device, because connection handler is only applicable for sd_ble_opt_get().[/quote]

Correct. You can set it as part of the initialization for the central device.

[quote user=""]4. Is that true default values of channel map 0xff,0xff,0xff,0xff,0x1f mean that adaptive frequency hopping is used?[/quote]

This channel map means that all data channels can be used. It will do frequency hopping, but it will by-default not be adaptive. To be adaptive, you would need to periodically update the channel map based on the measurements of the energy levels on the Bluetooth Low Energy channels. The Quality of service feature for channel monitoring in the SoftDevice can be used for this. See this link , you might find this repo useful.

[quote user=""]5. Is that true if I set, say, following map 0x00,0xff,0xff,0xff,0x1f this means channels from 0 to 7 will be used for connection [/quote]

Since you set ch_map[0] = 0x00; and ch_map[1] = 0xfe;, it will be 0 to 8. And based on my testing, it will be the other way around, 0 to 8 will not be used. Advertising channels are not used.

[quote user=""]6. When does a central device provide information about channel map to a peripheral device? My understanding is it happens on connection?[/quote]

Based on my testing, I see that the SoftDevice will shortly after the connection is established send a LL_CHANNEL_MAP_REQ packet with the updated channel map to the peripheral device.

[quote user=""]When I read channel map upon connection by using sd_ble_opt_get() I always get default values 0xff,0xff,0xff,0xff,0x1f.[/quote]

When I use the code you attached, and read the channel map some time after the BLE_GAP_EVT_CONNECTED I get this:

<info> app: err_code = 0, map 0,FE,FF,FF,1F

Try reading it after 1-2 seconds, and see if you get the expected result. If you have very long connection intervals, you might need to wait more than 1-2 seconds. If it does not work, I recommend using nRF Sniffer to analyze what is happening on-air. See this and this link.