nRF52840 - Device Reboots when BLE connection is terminated

RE: nRF52840 - Device Reboots when BLE connection is terminated

Priyanka — Thu, 03 Jul 2025 08:26:29 GMT

Hi Ricardo,

Ignoring critical errors does not seem like a good way to go. If you just remove NVIC_SystemReset() and continue after critical error, we cannot make any guarantees that SoftDevice will work as expected.

-Priyanka

RE: nRF52840 - Device Reboots when BLE connection is terminated

ricardo.oliveira — Wed, 02 Jul 2025 13:08:27 GMT

Hi.

Thanks for taking time to analyze the code.

So far what I did was redefine the __WEAK function that reboots the mcu, removing the NVIC_SystemReset().
it works now, and it doesn't hang or block the normal work of the mcu.

I also used it to print the error code and it has shown me 2 codes: Error 18 and Error 8.

Error 18 seems to be associated with advertising problems. I do use this code with a bigger app as central and peripheral, so it is in fact sending advertisement packets, but I didn't get what is the conflict it may be happening between disconnecting the Gap and advertisement packets.

About error 8 I honestly couldn't understand what may be going on.

RE: nRF52840 - Device Reboots when BLE connection is terminated

Priyanka — Wed, 02 Jul 2025 12:48:42 GMT

Hi Ricardo,

May be removing of APP_ERROR_CHECK is not a good idea to find out what is wrong? It might be helpful to do the opposite: add more error checks to find out why exactly it reboots. Can also replace all NVIC_SystemReset(); in error handling with for(;;){}; so it hangs instead of rebooting and then examine with debugger what exactly happens.

Not sure what that "GATT queue" is, it's not part of SoftDevice, probably some SDK module? In general, sd_ble_gap_disconnect() can be called any time and should just work.

We went through your app, can you make sure you don't have buffer overflow here?

case BLE_GATTC_EVT_READ_RSP:

{

uint8_t lengthDataRead = p_ble_evt->evt.gattc_evt.params.read_rsp.len;

memcpy(BufferDataRead, p_ble_evt->evt.gattc_evt.params.read_rsp.data, lengthDataRead);

//EVERYTHING GOES FINE UNTIL HERE

//BUT WHEN I TRY DO DISCONNECT IT, uC REBOOTS

sd_ble_gap_disconnect(myConnHandle, BLE_HCI_REMOTE_USER_TERMINATED_CONNECTION);

break;

}

Some examples set NRF_SDH_BLE_GATT_MAX_MTU_SIZE to high value, that may overflow 30 bytes they reserve in BufferDataRead.

-Priyanka

RE: nRF52840 - Device Reboots when BLE connection is terminated

Priyanka — Tue, 01 Jul 2025 12:32:48 GMT

Hi Ricardo,

I am discussing this internally and will get back to you. Please expect a slight delay as it is the summer holidays here in Norway.

Regards,

Priyanka

RE: nRF52840 - Device Reboots when BLE connection is terminated

ricardo.oliveira — Fri, 20 Jun 2025 13:04:48 GMT

Hi there.

Could you give an example of how I use the GATT queue? In the SDK examples code, they start the instance like this:

NRF_BLE_GQ_DEF(m_ble_gatt_queue,                                        /**< BLE GATT Queue instance. */
               NRF_SDH_BLE_CENTRAL_LINK_COUNT,
               NRF_BLE_GQ_QUEUE_SIZE);

But I don't know how to use that in the code, for instance, how can I queue the sd_ble_gattc_read() and sd_ble_gap_disconnect() so they don't overlap?

RE: nRF52840 - Device Reboots when BLE connection is terminated

Priyanka — Fri, 20 Jun 2025 12:44:15 GMT

Hi Ricardo,

If you have removed all APP_ERROR_CHECK calls and still experience reboots, the cause is likely a hard fault or assert elsewhere, possibly due to improper GATT operation sequencing or missing required initialization (such as the GATT queue). Using the GATT queue taht you mentioned is a good approach.

In your case, you're calling sd_ble_gattc_read() immediately after discovery, and later calling sd_ble_gap_disconnect() so there is a chance that they might overlap, especially if the beacon ends the connection suddenly. Without the GATT Queue, this can cause undefined behavior.

-Priyanka

RE: nRF52840 - Device Reboots when BLE connection is terminated

ricardo.oliveira — Thu, 19 Jun 2025 22:14:39 GMT

Also I noticed in an exemple of NUS that they use NRF_BLE_GQ_DEF (BLE GATT Queue instance). Should I use it? If so, how can I do that?

RE: nRF52840 - Device Reboots when BLE connection is terminated

ricardo.oliveira — Thu, 19 Jun 2025 22:09:06 GMT

I removed all APP_ERROR_CHECK of the whole code and still it reboots.

RE: nRF52840 - Device Reboots when BLE connection is terminated

Turbo J — Thu, 19 Jun 2025 09:00:14 GMT

SWD is usually required for production programming, I don't see why you can't use that here...?

APP_ERROR_CHECK reboots the device by default when there is no debugger connected. I believe you can reconfigure the SDK to skip the checks. There was also a method to print out errors using your own custom function, but that is not 100% reliable in case of stack overflows.

Probably simpler to port your code onto a DK board for testing the central stuff specifically.

You also want to learn Zephyr ASAP, there is very little support for the old SDK versions from this point forward.