central multilink example not building

RE: central multilink example not building

user113482 — Wed, 25 May 2022 09:54:39 GMT

Thank you, Simon

just checked prj.conf and realised that CONFIG_BT_MAX_CONN=20 is commented out - sorry my fault.

It is now be able to connect 2 with no error.

Flash usage is 35% and RAM 52%, use SoC 52833.

Now I need to keep a table of connected device with MAC addresses and their connection objects. will try to do connection and disconnect for any of them.

Thank you again.

Ping

RE: central multilink example not building

user75734 — Wed, 25 May 2022 08:07:45 GMT

A connection should not take that much RAM. How much flash memory does your application and the SoftDevice controller take? If it's close to the SoCs flash, the pairing information might exceed the flash available. Can you also show me the prj.conf file of your application?

Best regards,

Simon

RE: central multilink example not building

user113482 — Tue, 24 May 2022 08:13:22 GMT

Hi, Simon

1. I think conn_connecting is an instance of bt_conn in pointer type, right? definition below.

struct bt_conn *conn_connecting;

while it is created in following function -

err = bt_conn_le_create(addr, &create_param, &conn_param,

&conn_connecting);

and declaration of the function is :

int bt_conn_le_create(const bt_addr_le_t *peer,
		      const struct bt_conn_le_create_param *create_param,
		      const struct bt_le_conn_param *conn_param,
		      struct bt_conn **ret_conn)

it is a type of struct bt_conn **ret_conn, looks like a pointer of a pointer, I am bit confused here, and not sure which one is the connect object after a connection is created, please clarify.

2. About the SRAM usage, compile code uses ~30K RAM out of 128K,so there is still about 98K left, is there a way to know how much RAM a connection use? Please advise.

Thank you again for your patience!

Ping

RE: central multilink example not building

user75734 — Tue, 24 May 2022 06:23:25 GMT

1. Correct, but bt_conn *conn is not the same as conn_connecting, these are two different structs, and it seems like your're mixing these up.

2. It shouldn't be necessary to add conn_connecting. Use the bt_conn *conn struct instead.

3. Error -12 points to there being no more memory in your application. Have you checked how much memory your application uses as is, and does one connection take up what is available in your application?

Best regards,

Simon

RE: central multilink example not building

user113482 — Mon, 23 May 2022 07:56:23 GMT

Hi, Simon

Thanks for reply.

1. Here is the disconnect API in the example -static void disconnect(struct bt_conn *conn, void *data), it requires to pass bt_conn *conn object in order to call it, so I don't think it should be cleared before it is disconnected, Am I wrong?

2. Anyway, I tried to call the disconnect function with conn_connecting as parameter, and it works, but I had to modify the connected function, not to clear it. If I clear it . If I clear it to NULL and then call disconnect function, it crashes. Any solution to this?

3. I am keeping the MAC address of all connected devices, also tried to keep all connection objects too, so I can disconnect and connect any of them at any time, but so far it works for one connection at a time only, if I try to connect a second one while the first one is connected , it give me an error of -12, please can you tell me why?

Regards!

Ping

RE: central multilink example not building

user75734 — Mon, 23 May 2022 07:20:08 GMT

1. The disconnect doesn't use the conn_connecting call as far as I can see, but rather the connection handle or address of the device.

2. Yes, the conn_connecting is just an event used during the connection procedure, and are cleared between connections.

3. You need to store connection information, for example the addresses of the connected devices somewhere that you can call in order to disconnect from a specific device after connecting to multiple ones.

Best regards,

Simon

RE: central multilink example not building

user113482 — Thu, 19 May 2022 13:06:56 GMT

Hi, Simon

Thanks for your reply, I thought I need to create a new case to get some attention, good that you noticed - the new case has been closed anyway.

1. if conn_connecting is set to NULL after connection is still established, I wonder how can I call disconnect() function below if I need to disconnect it, the function needs to pass a connection object to work, it cannot be NULL, right?

void disconnect(struct bt_conn *conn)

2. Do you mean it will be overwritten by next connection? then back to question one, no connection object to refer to for disconnection. Do you mean I don't need to create multiple connection objects for multiple device connections? I need to disconnect them if I need.

3. Yes, you are right, I noticed, but I have not seen any object to disconnect, still don't quite understand how I can have a software to do multiple connect and disconnect for any device I choose, any more examples please?

Sorry to bother you with these questions, I am new to BLE and learning.

Ping

RE: central multilink example not building

user75734 — Thu, 19 May 2022 12:06:06 GMT

I see you also made a new case asking these same exact questions. In the future please create a new case if it's a separate topic or the older case was closed. Otherwise it's fine to ask in an existing post.

1. As far as I can tell, this is used when you connect to a device with bt_conn_le_create(). So when you get the connected event, either because of a failed connection attempt or a successful one (the second one), the conn_connecting has to be cleared so you can connect to the next device with a new connection object.

2. I don't think you need to, since this is cleared after a connection it is ready to be used by the next device that is connecting as well.

3. It should reach the "Disconnecting all" line and below when the iterations limit (max connections) are reached this can be reached as well as far as I can tell.

Best regards,

Simon

RE: central multilink example not building

user113482 — Wed, 18 May 2022 14:27:39 GMT

Hello, Simon

I am revisit the example here, and would like to ask a question, in call back function connected show below, I wonder why conn_connecting is set to NULL even there is no failure on connection, I am thinking of calling disconnect function to disconnect it if I need to, but if it is set to NULL, then, it is not possible, right? Also, may I create multiple connection reference variables like conn_connecting ? as I need to create multiple connections same time and freely disconnect them any time.

static void connected(struct bt_conn *conn, uint8_t reason)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	if (reason) {
		printk("Failed to connect to %s (%u)\n", addr, reason);

		bt_conn_unref(conn_connecting);
		conn_connecting = NULL;

		start_scan();
		return;
	}

	conn_connecting = NULL;  //why set the conn_connectign to NULL here? how can I disconnect it?

	conn_count++;
	if (conn_count < CONFIG_BT_MAX_CONN) {
		start_scan();
	}

	printk("Connected (%u): %s\n", conn_count, addr);

Last question - don't think the following code in init_central() function in while (true) {} loop is ever be called, I wonder how does the program disconnect the connected multiple devices.

		iterations--;
		printk("Iterations remaining: %u\n", iterations);

		printk("Disconnecting all...\n");
		is_disconnecting = true;
		bt_conn_foreach(BT_CONN_TYPE_LE, disconnect, NULL);

Could you please explain a little bit? I am trying to connect second device without setting the first conn_connecting NULL, and it gave me an error code of -12, seems meaning ENOMEM - not enough core, does this mean it has run out of memory? It only had 1 connection.

Thank you for your attention.

Ping

RE: central multilink example not building

user75734 — Fri, 08 Apr 2022 08:34:47 GMT

The radio will have to stop scanning while it is connecting to a device I'm afraid, as there is only one radio, it will have to stop scanning to be able to connect. If you want the device to always be scanning, you can't do connections, and only receive data from beacons. The error reasons can be found in the errno.h header file. -11 should point to EAGAIN, telling you to try again. What exact line is returning this error, as that usually gives a pointer as to what the reason is. I'm guessing you're being told to try creating the connection later (when the scanning has stopped), as the radio will be busy when you try scanning and creating a connection at the same time.

Best regards,

Simon

RE: central multilink example not building

user113482 — Thu, 07 Apr 2022 13:41:15 GMT

Hi, Simonr

Further on scan/connection, I noticed that it stops scan when it decides to connect to a device, I need my application always scan - is this possible? Do i need to create a scan only thread?

I tried to comment out the bt_le_scan_stop() before create connection, but it failed to connect, with reason -11, where can i find all the reason code for connect/disconnect please?

Regards!

Ping

RE: central multilink example not building

user113482 — Thu, 07 Apr 2022 09:43:52 GMT

Hello, Simonr

Thank you for your reply. below is the screenshot.

RE: central multilink example not building

user75734 — Thu, 07 Apr 2022 08:36:53 GMT

The CONFIG_BT_MAX_CONN can be set between 1 and 64, but is restricted by the size of the memory on the device you're using. The Zephyr sample sets it to close to max just because it's possible, but it has to be modified when using devices with less memory. Can you show me the build error you get when trying to set the max connection to more than 20?

Regarding the scanning, the central_multilink will start scanning, then connect to the first connectable device with an RSSI better than -35dBm. Once the connection is completed, the device will start scanning again and connect to the next connectable advertising device with good enough RSSI. This will go on until the max connections are reached I think (or there are no more suitable peripherals to connect to.

Best regards,

Simon

RE: central multilink example not building

user113482 — Thu, 07 Apr 2022 07:41:22 GMT

Thank you for reply!

So CONFIG_BT_MAX_CONN is depend on SoC?

32 doesn't compile neither, maximum 20 for me, I wonder where I can find the limit for different boards.

Regards!

Ping

RE: central multilink example not building

user103465 — Wed, 06 Apr 2022 16:43:34 GMT

Another question, when a central is connected to some peripherals, is it still able to do scanning?

Yes it is able to scan.

CONFIG_BT_MAX_CONN = 62 is too high value. About 32 is maximum for nrf52

CONFIG_BT_MAX_CONN = 62 is for other board sample