BLE_GAP_EVT_CONNECTED event is not triggered

[Rekha]

Hi all,

I have checked in Nordic Devzone for this query but no luck in finding solution for my query.

I am using nrf52832 and configured as central and peripheral.

my device will scan and store peer address in flash and then connect to stored address later.

when i connect to peer address using sd_ble_gap_connect it returns NRF_SUUCESS but BLE_GAP_EVT_CONNECTED  is not triggered.

this issue occurs only for some peripherals and some peripheral i can able to connect and it triggers event as well.

tested with one of the example code: when i try to connect  peripheral  device programmed with ble_app_uart code this issue occurs where  BLE_GAP_EVT_CONNECTED  is not triggered.

but the same peripheral connects successfully through my Android phone.

i am unable understand what is the issue.

Please guide...

Thanks

Rekha

[Einar Thorsrud]

Hi,

You should always get either BLE_GAP_EVT_CONNECTED or BLE_GAP_EVT_TIMEOUT unless you cancel the connection by a call to sd_ble_gap_connect_cancel(), as you can see from this MSC. Can you share your code so that we can check to see if there is any possibility of you canceling the connection or missing an event?

[Rekha]

Hi i changed scan parameter timeout = 0x01 instead of 0. now i am getting ble gap event timeout error in BLE_GAP_EVT_TIMEOUT event.

How to solve

Thanks

[Rekha]

Hi

Einar Thorsrud said:

Can you elaborate the question?

i want any kind of indication if my device is not getting connected after some time . can i specify particular amount of time as wait time for connection?

i want to wait for some time and then jump connecting to next device as per my application.

is time out error is the only indication if connection fails ?

Thanks

[Einar Thorsrud]

Rekha said:

i want any kind of indication if my device is not getting connected after some time . can i specify particular amount of time as wait time for connection?

Yes, this is the timeout parameter that you have experimented with (first setting it to 0, then to 1). This specifies the timeout in 10 ms intervals. For example:

• 0: no timeout
• 1: 10 ms timeout
• 20: 200 ms timeout 

Rekha said:

is time out error is the only indication if connection fails ?

 Yes.

[Rekha]

Hi 

i have not achieved my requirement yet.

is it possible to connect more than one device at a time with scan paramter timeout set to 0.

try to connect multiple device at the same time.

how to achieve this ?

because if i connect first device i unable to connect next since timeout is set to 0.

how to achieve multiple connection simultaneously having an array of MAC address with me?

Thanks

[Einar Thorsrud]

Hi,

Scanning will stop once you connect to a peripheral, regardless of which timeout value you set. Therefore you need to restart scanning if you want to connect to another.

[Rekha]

HI I already have an array of MAC ID to be connected so even if scan stops i will still be able to connect to devices using MAC ID.

the MAC addresses are stored in flash. i am retrieving stored MAC address and connecting the devices.

I am not scanning for the devices while connecting.

Thanks.

[Einar Thorsrud]

I understand. I was not clear in my previous reply, but the point is that sd_ble_gap_connect() will initiate scanning in order to connect. That is due to how connections work in BLE, where the peripheral advertises, and the central has to send a connection request within a short window after the advertising packet. To be clear: You have to call sd_ble_gap_connect() again in order to connect to a second peripheral (and so on).

[Rekha]

Hi Thank you for the detailed explaination. Now i understand the connection process better.

Einar Thorsrud said:

You have to call sd_ble_gap_connect() again in order to connect to a second peripheral (and so on).

As you said I am calling sd_ble_gap_connect() in a loop. only for the first time it returns NRF_SUCCESS and next time for other devices it returns INVALID_STATE (in my case: may be because of first device is still searching for a connection) so how to overcome this issue without changing timeout.

Thanks 

[Einar Thorsrud]

Hi,

You cannot do this in a loop. You have to wait for a BLE_GAP_EVT_CONNECTED or BLE_GAP_EVT_TIMEOUT event before you can call sd_ble_gap_connect() for the second time.

[Rekha]

Hi 

That is where the risk is - if i set timeout device is not getting connected within that short span. hence i disabled timeout. suppose peripheral device is not in the vicinity, even then my device will still wait for the connection therefore i am unable to connect to next devices.

How much time does a central requires to connect peripheral?

Thanks

[Einar Thorsrud]

Rekha said:

That is where the risk is - if i set timeout device is not getting connected within that short span. hence i disabled timeout. suppose peripheral device is not in the vicinity, even then my device will still wait for the connection therefore i am unable to connect to next devices.

 Yes. That is why a timeout is usually sensible.

Rekha said:

How much time does a central requires to connect peripheral?

The time depends on the advertising interval of the peripheral, and the RF environment (noise/interference), which can lead to packet loss. This is because you have to receive an advertising packed in order to connect, and then send a successful connection request. If the time between advertisement packets (advertising interval) is long, or packets are lost, it will take longer time to connect. This are all inherent properties of BLE, and not directly related to the nRF devices.