CAF BLE state BT connection limit

RE: CAF BLE state BT connection limit

tellg — Thu, 21 Jul 2022 21:40:36 GMT

But the scan library is needed if one wants to use scan filters, and that library needs CONFIG_BT_SCAN, which again needs CONFIG_BT_CENTRAL, and then we are back again to the build assert in the CAF module ble_state.c. Would it be possible to change that build assert test. I am using ncs 2.0.0

I posted a new issue on devzone for this: CAF BLE state module build assert when CONFIG_BT_PERIPHERAL and CONFIG_BT_CENTRAL is set

RE: CAF BLE state BT connection limit

langestefann — Fri, 30 Jul 2021 14:52:32 GMT

This works great. Thanks a lot!

RE: CAF BLE state BT connection limit

Simon — Fri, 30 Jul 2021 07:50:15 GMT

Check out the sample I attached, where I use the function bt_le_scan_start() without enabling CONFIG_BT_SCAN or CONFIG_BT_CENTRAL.

The function bt_le_scan_start() is declared in zephyr/include/bluetooth/bluetooth.h (not scan.h) and defined in zephyr/subsys/bluetooth/host/scan.c.

The file zephyr/subsys/bluetooth/host/scan.c is intergrated into the project due to CONFIG_BT_OBSERVER: https://github.com/nrfconnect/sdk-zephyr/blob/v2.6.0-rc1-ncs1/subsys/bluetooth/host/CMakeLists.txt#L44-L47

RE: CAF BLE state BT connection limit

langestefann — Thu, 29 Jul 2021 10:11:25 GMT

Thanks for your quick reply, this clears some things up. I am relatively new to BLE so happy to learn new things.

I am still a bit confused about the term 'scanning', since in my project I had set CONFIG_BT_SCAN=y, but this has a direct dependency on BT_CENTRAL=y.

Do you know if I can still use the scanning module (https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/include/bluetooth/scan.html) in my project?

Since I had build my scanning code around this module and now the code will no longer build. Should I just use

bt_le_scan_start()
bt_le_scan_stop()

directly? Or do you have a better suggestion?

Again, many thanks

RE: CAF BLE state BT connection limit

Simon — Thu, 29 Jul 2021 09:36:14 GMT

[quote user=""]- Be a central so that I can scan for advertising packets from other BLE sensors. I will never connect, I just need to be able to parse the advertisement data.[/quote]

If you just want the device to scan without connection, you should not configure it as a central. As mentioned in the ticket What is a client and server in BLE?, the central role has to do with establishing a connection. Instead you should configure it as an observer, which is the non-connecting variant of a central.

I modified the sample ncs/zephyr/samples/bluetooth/central to make it operate as an observer. I used NCS v1.6.0, and here is the diff:

diff --git a/samples/bluetooth/central/prj.conf b/samples/bluetooth/central/prj.conf
index 3e36a99938..091c338db6 100644
--- a/samples/bluetooth/central/prj.conf
+++ b/samples/bluetooth/central/prj.conf
@@ -1,2 +1,4 @@
 CONFIG_BT=y
-CONFIG_BT_CENTRAL=y
+CONFIG_BT_OBSERVER=y
\ No newline at end of file
diff --git a/samples/bluetooth/central/src/main.c b/samples/bluetooth/central/src/main.c
index c2a164cccb..f58203f145 100644
--- a/samples/bluetooth/central/src/main.c
+++ b/samples/bluetooth/central/src/main.c
@@ -14,49 +14,21 @@
 
 #include <bluetooth/bluetooth.h>
 #include <bluetooth/hci.h>
-#include <bluetooth/conn.h>
 #include <bluetooth/uuid.h>
 #include <bluetooth/gatt.h>
 #include <sys/byteorder.h>
 
 static void start_scan(void);
 
-static struct bt_conn *default_conn;
-
 static void device_found(const bt_addr_le_t *addr, int8_t rssi, uint8_t type,
                         struct net_buf_simple *ad)
 {
        char addr_str[BT_ADDR_LE_STR_LEN];
        int err;
 
-       if (default_conn) {
-               return;
-       }
-
-       /* We're only interested in connectable events */
-       if (type != BT_GAP_ADV_TYPE_ADV_IND &&
-           type != BT_GAP_ADV_TYPE_ADV_DIRECT_IND) {
-               return;
-       }
 
        bt_addr_le_to_str(addr, addr_str, sizeof(addr_str));
        printk("Device found: %s (RSSI %d)\n", addr_str, rssi);
-
-       /* connect only to devices in close proximity */
-       if (rssi < -70) {
-               return;
-       }
-
-       if (bt_le_scan_stop()) {
-               return;
-       }
-
-       err = bt_conn_le_create(addr, BT_CONN_LE_CREATE_CONN,
-                               BT_LE_CONN_PARAM_DEFAULT, &default_conn);
-       if (err) {
-               printk("Create conn to %s failed (%u)\n", addr_str, err);
-               start_scan();
-       }
 }
 
 static void start_scan(void)
@@ -73,54 +45,6 @@ static void start_scan(void)
        printk("Scanning successfully started\n");
 }
 
-static void connected(struct bt_conn *conn, uint8_t err)
-{
-       char addr[BT_ADDR_LE_STR_LEN];
-
-       bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
-
-       if (err) {
-               printk("Failed to connect to %s (%u)\n", addr, err);
-
-               bt_conn_unref(default_conn);
-               default_conn = NULL;
-
-               start_scan();
-               return;
-       }
-
-       if (conn != default_conn) {
-               return;
-       }
-
-       printk("Connected: %s\n", addr);
-
-       bt_conn_disconnect(conn, BT_HCI_ERR_REMOTE_USER_TERM_CONN);
-}
-
-static void disconnected(struct bt_conn *conn, uint8_t reason)
-{
-       char addr[BT_ADDR_LE_STR_LEN];
-
-       if (conn != default_conn) {
-               return;
-       }
-
-       bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
-
-       printk("Disconnected: %s (reason 0x%02x)\n", addr, reason);
-
-       bt_conn_unref(default_conn);
-       default_conn = NULL;
-
-       start_scan();
-}
-
-static struct bt_conn_cb conn_callbacks = {
-               .connected = connected,
-               .disconnected = disconnected,
-};
-
 void main(void)
 {
        int err;
@@ -133,7 +57,7 @@ void main(void)
 
        printk("Bluetooth initialized\n");
 
-       bt_conn_cb_register(&conn_callbacks);
+       //bt_conn_cb_register(&conn_callbacks);
 
        start_scan();
 }