Bluetooth cannot send data packets within the connection interval.

[HHJ]

Our company has previously used the NRF52840, and we know that by modifying the GAP event length (NRF_SDH_BLE_GAP_EVENT_LENGTH), we can enable Bluetooth to transmit multiple data packets within one connection interval. Currently, our NRF5340 is encountering a similar issue: when its transmission speed is greater than the connection interval, it can send normally, but when its transmission speed is less than the connection interval, there will be cases where data packets fail to send (just like packet loss). We want to know what parameters can be configured in NRF5340 with nrf connect v3.1.0 to achieve the effect of GAP event length. We hope you can help us

[HHJ]

I have checked the prj.conf of my ipc_radio, and all the key configurations from the file at v3.1.0\nrf\samples\bluetooth\throughput\sysbuild\ipc_radio\prj.conf have been included in mine.

Interestingly, when my timer K_MSEC() is set to 4 and the connection interval is set to 7.5ms, data packets do not queue (-12), but the rate is 3.8ms, which does not meet our target of 3ms. When K_MSEC() is set to 4 and the connection interval is 15ms, data packets start to queue (approximately 2 out of every 5 packets are queued). When K_MSEC() is set to 3 and the connection interval is 7.5ms, data packets also queue (roughly 1 out of every 3 packets is queued). If K_MSEC() is set to 3 and the connection interval is 15ms, even more data packets will queue.

This seems very much like a blockage at the TX (transmit) end. Regrettably, however, adjusting the value of CONFIG_BT_BUF_ACL_TX_COUNT does not result in any observable changes.

[Edvin]

Can you please zip and upload your peripheral and central application, so that I can have a look?

HHJ said:

approximately 2 out of every 5 packets are queued

When you list numbers like this. Does 3 out of every 5 packets return -12 when you try to queue them?

BR,
Edvin

[HHJ]

Thanks bro

Our problem has been solved.

BR

kevin