Reset the channel sounding parameters after a disconnection

RE: Reset the channel sounding parameters after a disconnection

Edvin — Wed, 11 Mar 2026 08:22:47 GMT

I am not sure channel sounding is the best option if you plan to support 100's of connections. Bluetooth Low Energy even without channel sounding is challenging to maintain that many connections (probably impossible).
You can read about the scheduling in the link in my previous reply.

One option is probably to reconnect/disconnect whenever you change the device, but it will not be as fast, so you will not be able to get channel sounding data from all 100 devices that often. It depends on the use case. For tracking location in a storage, it might be fine, but not for real time locationing of a lot of devices.

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Application Ninja — Sat, 07 Mar 2026 23:06:07 GMT

I know it's not correct to comment another persons thread, but I am commenting directly on this sample here... 🙂

So for this two connection example, it really doesn't scale well, due to the large buffer requirements of latest_local_steps_storage and latest_peer_steps_storage.

How can Channel Sounding be effectively used to support 100's of connections then?

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Fri, 06 Mar 2026 09:37:58 GMT

Thanks for the information, Edvin.
Now I see that the problem of mismatch and disconnection actually lies in the scheduling of the events. I will port to v3.2.2

Regards,
Vinayaka KS

RE: Reset the channel sounding parameters after a disconnection

Edvin — Thu, 05 Mar 2026 09:46:32 GMT

Hello,
Yes, I see that this doesn't build out of the box with v3.1.x, but it builds for v3.2.x. There are some API changes to the changes in the channel sounding API.

It was our Channel Sounding team that suggested that I used 3.2, because they were not sure it would work with multiple connections in v3.1.x.

They also suggested to have a look at this:

https://docs.nordicsemi.com/bundle/ncs-latest/page/nrfxlib/softdevice_controller/doc/scheduling.html#channel_sounding_timing

But that document doesn't exist for NCS v3.1.x.

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Wed, 04 Mar 2026 10:12:22 GMT

Hi Edvin,
This works as intended on v3.2.2.

I tried to test it on v3.1.1, and it had build issues. I might have to port my existing code to the new version of NCS.

Regards,
Vinayaka KS

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Mon, 02 Mar 2026 11:43:32 GMT

Thanks, Edvin,
I will test it from my side.

I will use v3.1.1 first and try, if it doesnt then I will test it on v3.2.2

Regards,
Vinayaka

RE: Reset the channel sounding parameters after a disconnection

Edvin — Mon, 02 Mar 2026 11:27:00 GMT

Hello,

Attached is a modified initiator sample that handles two connections, and starts channel sounding once it is connected to two reflectors. It is written for NCS v3.2.2. Perhaps you can give it a go, and let me know if it works on your end.

Note that it doesn't have the NUS service along side it. You would need to add that to your application if you want it.

devzone.nordicsemi.com/.../init_5F00_2_5F00_conn.zip

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Wed, 25 Feb 2026 12:16:47 GMT

Okay, Thanks.
If it works in 3.2.0, I will probably port.

Regards,
vinayaka KS

RE: Reset the channel sounding parameters after a disconnection

Edvin — Wed, 25 Feb 2026 11:35:18 GMT

Ah, I see. I am looking into this, but it may be that this is simply not supported in NCS v3.1.1 (multiconnection channel sounding). I will try to port it to 3.2.0, and see if that changes anything.

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Mon, 23 Feb 2026 15:05:28 GMT

It's printing over the UART, and it's getting generated in the reflector and sent via NUS.

And thanks for the update.

Regards,

Vinayaka KS

RE: Reset the channel sounding parameters after a disconnection

Edvin — Mon, 23 Feb 2026 14:48:24 GMT

Hello,

Where is "Data from Reflector 1" printed from? I couldn't find it.

I was able to reproduce it, yes. I am discussing this with our channel sounding team. I will get back to you as soon as I know more. I am sorry for the delay.

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Thu, 19 Feb 2026 10:35:50 GMT

Hi Edvin, were you able to recreate the issue?

Regards,

Vinayaka

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Tue, 17 Feb 2026 16:03:48 GMT

Can this be a scheduling problem?

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Fri, 13 Feb 2026 14:04:13 GMT

Hi, Its okay,

I have updated the code base now. I will share that with you.
The build command I am using is

west build --build-dir cs/central_uart --pristine --board nrf54l15dk/nrf54l15/cpuapp --sysbuild -- -DCONF_FILE="prj.conf" -DDEBUG_THREAD_INFO=On -DCONFIG_DEBUG_THREAD_INFO=y -Dcentral_uart_DEBUG_THREAD_INFO=On

Yes, if you run the reflector and initiator with my code, you should be able to recreate the issue.

Thanks,

Vinayaka KS

RE: Reset the channel sounding parameters after a disconnection

Edvin — Fri, 13 Feb 2026 13:19:35 GMT

Hello,

Sorry for my previous reply. It was a bit off. It was originally intended for another ticket, and I thought it could be the same issue, as they were also trying to range between multiple reflectors/initiators (but alternating, by disconnecting from them).

I tried to build your applications, but I couldn't. I got a build error. Can you please let me know what NCS version you are using, and what build command you are using. If you are using nRF Connect for VS Code, you can copy the build command by right clicking the build folder and select "Copy build command" in VS Code.

And is my understanding correct:

If I build your applications, flash the central_uart... to one nRF54L15 DK, and the reflector to two other nRF54L15 DKs, I should be able to see the issue that you are seeing?

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Tue, 10 Feb 2026 22:16:54 GMT

The reason why I ask for counter reset on the reflector is that I always have this ranging counter mismatch or empty step data when I start measurement to the device 0 (which gets connected first). I have some logs below.

I even use 2 Config_IDs to differentiate between these devices

There are supposed to be at least 19 samples of distance measurement data, since I read and print distance results once every 500ms and switch between devices once every 10 seconds. But, I see this error either from the ranging_data_cb() or from the bt_ras_rreq_rd_subevent_data_parse()

I: Disabling the CS procedure
I: counters reset, local:-1, dropped:-1
W: Procedure 584 aborted, reason - 0x1
I: CS procedures disabled.
I: Enabling the CS procedure
I: Sounding to device 0
I: CS procedures enabled:
- config ID: 0
- antenna configuration index: 0
- TX power: 0 dbm
- subevent length: 28198 us
- subevents per event: 1
- subevent interval: 0
- event interval: 2
- procedure interval: 5
- procedure count: 0
- maximum procedure length: 1000
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 691, local: 690)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 692, local: 691)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 693, local: 692)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 694, local: 693)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 695, local: 694)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 696, local: 695)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 697, local: 696)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 698, local: 697)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 699, local: 698)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 700, local: 699)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 701, local: 700)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 702, local: 701)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 703, local: 702)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 704, local: 703)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 705, local: 704)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 706, local: 705)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 707, local: 706)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 708, local: 707)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 709, local: 708)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 710, local: 709)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 711, local: 710)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 712, local: 711)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 713, local: 712)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 714, local: 713)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 715, local: 714)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 716, local: 715)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 717, local: 716)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 718, local: 717)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 719, local: 718)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 720, local: 719)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 721, local: 720)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 722, local: 721)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 723, local: 722)
Data from Reflector 2
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 724, local: 723)
Data from Reflector 1
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 725, local: 724)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 726, local: 725)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 727, local: 726)
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 728, local: 727)
I: Disabling the CS procedure
I: counters reset, local:-1, dropped:-1
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 729, local: 4294967295)
I: CS procedures disabled.
I: Enabling the CS procedure
I: Sounding to device 1
I: CS procedures enabled:
- config ID: 1
- antenna configuration index: 0
- TX power: 0 dbm
- subevent length: 28198 us
- subevents per event: 1
- subevent interval: 0
- event interval: 2
- procedure interval: 5
- procedure count: 0
- maximum procedure length: 1000
I: Dropped subevent results. Waiting for ranging data from peer.
I: Ranging data dropped as peer ranging counter doesn't match local ranging data counter. (peer: 585, local: 728)
I: 1.756596,3.513278,2.610804,2.604011
I: 1.756596,3.427624,2.751654,2.049362
I: 2.049362,3.427624,2.837012,2.049362
I: 2.049362,3.427624,2.837012,2.049362
I: 2.049362,3.427624,2.854575,2.049362
I: 2.049362,3.427624,2.854575,2.049362
I: 2.049362,3.451425,3.105397,2.049362
I: 2.049362,3.534048,3.157910,2.049362
I: 2.049362,3.534048,3.105397,2.049362
I: 2.049362,3.534048,3.157910,2.049362
I: 2.049362,3.546767,3.382754,2.049362
I: 2.049362,3.424742,3.265795,2.049362
I: 2.049362,3.424742,3.265795,2.049362
I: 2.049362,3.424742,2.969308,2.049362
Data from Reflector 2
Data from Reflector 1
I: 2.049362,3.360484,2.927473,2.049362
I: 2.049362,3.360484,2.792185,2.342129
I: 2.195745,3.360484,2.820416,2.342129
I: Disabling the CS procedure
I: counters reset, local:-1, dropped:-1
W: Procedure 623 aborted, reason - 0x1
I: CS procedures disabled.
I: Enabling the CS procedure
I: Sounding to device 0
I: CS procedures enabled:
- config ID: 0
- antenna configuration index: 0
- TX power: 0 dbm
- subevent length: 28198 us
- subevents per event: 1
- subevent interval: 0
- event interval: 2
- procedure interval: 5
- procedure count: 0
- maximum procedure length: 1000
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
Data from Reflector 2
E: empty step data
Data from Reflector 1
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
E: empty step data
I: Disabling the CS procedure
I: counters reset, local:-1, dropped:-1
E: empty step data
I: CS procedures disabled.
I: Enabling the CS procedure
I: Sounding to device 1
I: CS procedures enabled:
- config ID: 1
- antenna configuration index: 0
- TX power: 0 dbm
- subevent length: 28198 us
- subevents per event: 1
- subevent interval: 0
- event interval: 2
- procedure interval: 5
- procedure count: 0
- maximum procedure length: 1000
I: 2.049362,3.392859,2.921039,2.049362
I: 2.049362,3.392859,3.176355,2.049362

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Tue, 10 Feb 2026 08:07:21 GMT

Hey, I tried it out, and It doesnt work. Also, I don't think this is something related because I don't disconnect the reflector, but stay connected and do the procedure consecutively with another reflector.

Is there a specific way to reset my local counters on the reflector ? Either via the initiator or on the reflector directly?

RE: Reset the channel sounding parameters after a disconnection

Edvin — Mon, 09 Feb 2026 14:37:15 GMT

Ok, I did find an issue. You are restarting the the advertising directly in the .recycled callback.

I saw that the channel_sounding_ras_reflector sample just rebooted in the disconnected_cb event. This is a quick (and dirty) way to just reset the state of the reflector. But of course, this is maybe not allwals desireable.

Attached is a modified channel_sounding_ras_reflector sample (tested in NCS v3.2.1):

devzone.nordicsemi.com/.../cs_5F00_refl.zip

Note that the recycled_cb() calls advertising_start(), but this doesn't directly call bt_le_adv_start(). This needs to be done through a work handler, like it is done in e.g. the NCS\nrf\samples\bluetooth\peripheral_uart sample. It is a bit more lines of code, but the idea is that you can't call BT API directly from the recycled callback, as it will block itself. Therefore you need to add these small pieces of code:

// in main.c:

static struct k_work adv_work;

...

static void adv_work_handler(struct k_work *work)
{
	int err = bt_le_adv_start(BT_LE_ADV_CONN_FAST_2, ad, ARRAY_SIZE(ad), NULL, 0);
	if (err) {
		LOG_ERR("Advertising failed to start (err %d)", err);
		return;
	}
}

...

static void recycled_cb(void)
{
	LOG_INF("Connection object available from previous conn. Disconnect is complete!");
	advertising_start();
}

BT_CONN_CB_DEFINE(conn_cb) = {
	...
	.recycled = recycled_cb,
};

...

int main(void)
{
...
	k_work_init(&adv_work, adv_work_handler);
	advertising_start();
...
}

Try that, and let me know if it doesn't work.

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Mon, 09 Feb 2026 09:21:07 GMT

I found the issue, I was not setting one config

CONFIG_BT_CTLR_CHANNEL_SOUNDING=y

And now I can sound, but the device has problems like this.
W: Mismatch of local and peer step mode 1 != 2
E: empty step data
E: empty step data

This happens to the device that gets connected first, and happens every time I sound it. The 2nd device is able to get the data.

RE: Reset the channel sounding parameters after a disconnection

Fhar — Fri, 06 Feb 2026 10:28:36 GMT

Hi Vinayaka, have you got any update on your attempts to do multi connection channel sounding ? I am also trying to do it but unfortunately, without success.
Regards,
Fhar

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Wed, 04 Feb 2026 13:16:31 GMT

I have sent both the peripheral and central.

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Thu, 29 Jan 2026 10:08:53 GMT

Sure, I can send it to you

RE: Reset the channel sounding parameters after a disconnection

Edvin — Thu, 29 Jan 2026 09:40:56 GMT

I don't have a multi-connection channel sounding sample at hand. Do you mind sending me what you already have, then perhaps I can have a look at it, and give it a go.

I will not be able to look into it tomorrow, but hopefully during the beginning of next week.

Best regards,

Edvin

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Thu, 29 Jan 2026 07:21:18 GMT

I am not able to enable the CS procedures for the 2nd device. Is this a problem with the memory?

I: Disabling the CS procedure
I: Free rreq 0x20002b18 for conn 0x200076d8
I: CS procedures disabled.
W: opcode 0x2094 status 0x07
I: Enabling the CS procedure
E: Failed to enable CS procedures (err -5) for Device1

void switch_CS_device(void){
	int err;
	while (1) {
		k_sleep(K_SECONDS(10));

		if(cs_device_count > 1){
			node_index_val = (node_index_val+1)%2; 

			struct bt_le_cs_procedure_enable_param enable_params = {
				.config_id = CS_CONFIG_ID,
				.enable = BT_CONN_LE_CS_PROCEDURES_ENABLED,
			};

			struct bt_le_cs_procedure_enable_param disable_params = {
				.config_id = CS_CONFIG_ID,
				.enable = BT_CONN_LE_CS_PROCEDURES_DISABLED,
			};

			err = bt_le_cs_procedure_enable(conn_contexts[(node_index_val+1)%2].conn, &disable_params);
			LOG_INF("Disabling the CS procedure");
			if (err) {
				LOG_ERR("Failed to disable CS procedures (err %d) for Device%d", err,node_index_val);
				return;
			}
			k_sem_take(&sem_cs_enable_disable,K_FOREVER);

			most_recent_local_ranging_counter = PROCEDURE_COUNTER_NONE;
			dropped_ranging_counter = PROCEDURE_COUNTER_NONE;
			buffer_index = 0;
			buffer_num_valid = 0;
			
			// Reset step buffers
			net_buf_simple_reset(&latest_local_steps);
			net_buf_simple_reset(&latest_peer_steps);
			
			// Clear distance estimate buffer
			memset(distance_estimate_buffer, 0, sizeof(distance_estimate_buffer));
			
			// Reset semaphores to clean state
			k_sem_reset(&sem_local_steps);
			k_sem_give(&sem_local_steps);
			bt_ras_rreq_free(conn_contexts[(node_index_val+1)%2].conn);
			k_msleep(1000);

			err = bt_le_cs_procedure_enable(conn_contexts[node_index_val].conn, &enable_params);
			LOG_INF("Enabling the CS procedure");
			if (err) {
				LOG_ERR("Failed to enable CS procedures (err %d) for Device%d", err,node_index_val);
				return;
			}
			else{
				LOG_INF("Sounding to device%d", node_index_val);
			}
			k_sem_take(&sem_cs_enable_disable,K_FOREVER);
		}
	}
}

RE: Reset the channel sounding parameters after a disconnection

Vinayaka KS — Tue, 27 Jan 2026 14:16:16 GMT

Thanks a lot, I will try implementing this now.

Regards,

Vinayaka KS