ERROR 18 [NRF_ERROR_CONN_COUNT] crash after forcing disconnect

[Olfox]

Hi,

I try to implement a disconnection after wrote a characteristic parameter. This byte change the working mode of my systeme.

So user connect, write the field to change mode. Then in on_write function , i close some timer and close twi module and  force disconnection with ble_conn_state_for_each_connected(disconnect, NULL);     .

Before force disconnect, i started a timer that will allow to wake up systeme each 20sec , advertise, and allow phone to get data before to enter sleep again, and this infinitely .

But after the first wake up and first advertising this error happens:

<info> app: ADVERTISING...
<error> app: ERROR 18 [NRF_ERROR_CONN_COUNT] at C:\nordic\nRF5SDK160098a08e2\examples\ble_peripheral\Firmware\main.c:918
PC at: 0x00031B91
<error> app: End of error report

Its is triggered by uint32_t err_code = ble_advertising_start(&m_advertising, BLE_ADV_MODE_FAST);
APP_ERROR_CHECK(err_code);

It seems to be related to the number of connexion. But i'm already disconnected  with the own client connected , my phone. Moreover, i remember to have set three max connexion client at a time ( even if i was only able to have only one at a time but i will investigate this further)

DO you have an idea how to manage properly disconnexion? i thought to do it well by using ble_conn_state_for_each_connected(disconnect ... 

Thank you !!!

[Edvin]

Hello,

What is your NRF_SDH_BLE_TOTAL_LINK_COUNT and your NRF_SDH_BLE_PERIPHERAL_LINK_COUNT set to in sdk_config.h?

At the time when the application fails with the log that you posted. How many devices were connected at that point?

If you are not sure how many devices that are connected, please try to count the amount of BLE_GAP_EVT_CONNECTED and BLE_GAP_EVT_DISCONNECTED events from your ble_evt_handler.

From where is this advertisement start called? Where do you print "ADVERTISING" in your log? Is that from the timeout interrupt?

[Olfox]

Hi Edvin 

Thanks for the support, i have found this problem, it was linked to my " state machine" . A kind of confusion between advertising timeout duration and restart of advertising cumulated to bad synchronisation with deconnexion. I'm doing all in event handler now , it is clean and efficent from a power saving point of view( no cpi wake up). I only have to respect important rules like, advertising time should not be bigger than timeout + traetment etc but it is directly linked to my application, i can manage :) .

1. Multi user connect question

NRF_SDH_BLE_TOTAL_LINK_COUNT and NRF_SDH_BLE_PERIPHERAL_LINK_COUNT   are set to 1 (i thought to have change it in the past but no sorry). As i'm only peripheral, what is difference between both please ? i guess total link is for uC doing the job of central + peripheral  et the same time ?

I'm also wondering in case of multi user connexion how the code i wrote will react , cause i'm doing all in event handler, but nothing specify for which connexion .

PRACTICAL CASE : If one user connect, he will start sensor supply and communication because of the connect. Now imagine a second user connect too, he will also call the supply sensors fonction, not perfect but ok should not cause issue. Now imagine the first user disconnect, normally , as it is written at the moment, sensors will be switch off. But second user, will not see sensors data updating anymore, as communication and supply have been previoulsy closed !

So i imagine that i have to check everywhere if number of connexion live is superior to one before to switch off sensors ?

2. Advertising parametre question

A second criteria alert me:

APP_ADV_DURATION x (10ms) : occurs timeout after x 10* ms : ok works fine.

CONN_SUP_TIMEOUT : but what about this 4second then?

Thank you very much , as usual , for the great support of all your team , you bring a real help to us !

[Edvin]

Olfox said:

As i'm only peripheral, what is difference between both please ? i guess total link is for uC doing the job of central + peripheral  et the same time ?

 That is correct. You can set NRF_SDH_BLE_TOTAL_LINK_COUNT = NRF_SDH_BLE_PERIPHERAL_LINK_COUNT + NRF_SDH_BLE_CENTRAL_LINK_COUNT if you like, but I guess the reason it is not is that you can support e.g. 8 connections that can be either peripheral or central, but not 8 of each at the same time. 

 

Olfox said:

So i imagine that i have to check everywhere if number of connexion live is superior to one before to switch off sensors ?

 I guess you can look at the SDK\examples\ble_peripheral\experimental\ble_app_multiperipheral example for inspiration. Look at how the

ble_evt_handler() -> case BLE_GAP_EVT_CONNECTED -> on_connected()

checks the periph_link_cnt and uses this parameter to decide whether to restart advertising. Similarly, you can use it to check whether you should start or stop the sensors.

If your on_connected() is called with periph_link_cnt = 1, it means that it was 0 before that, and you should start the sensors. If on_disconnected() is called with periph_link_cnt = 0 it means that the last connection disconnected, and you can stop the sensors.

CONN_SUP_TIMEOUT is the time that it takes for the connection to disconnect if the other device stops responding (runs out of battery, is turned off, moves out of range) without sending a disconnect packet.

If you try to connect to the peripheral with a central (either another nRF or a phone), and they agree on 4 seconds CONN_SUP_TIMEOUT, and then you just power off the nRF, you will see that it takes 4 seconds for the phone to say that it is disconnected. During these 4 seconds, the central will continue to look for BLE packets from the peripheral, and resume normal operation if a packet is received. The reason for this is that the link should be robust against packet loss due to noise (various sources such as obstacles, walls, long distance, other radio transmitting sources such as WiFi, etc.).

Hopefully, this clears up your questions. Let me know if anything was unclear.

BR,

Edvin

[Olfox]

All is perfect , thanks Edvin ! 

Just one last, if 2 client are connected, does it consume two times more? ( i measure avg 300uA in connected status with one device).

[Edvin]

Not two times as much, but it would use a bit more, since it would have to use the radio about twice as much. 

You can take a look at the online power profiler and look at how much current is spent on the radio for one connection with your connection parameters. This would double, but the amount of current used for your other peripherals, clocks, timers and so on would not double.

BR,

Edvin

[Olfox]

Great thank you Edvin !