Multiple Peripheral Setting

[masterLee]

Hi, My system has 5 nRF52840 peripherals connected to one central device (PC app).

In the peripheral's sdk_config.h there is a macro NRF_SDH_BLE_PERIPHERAL_LINK_COUNT 1

Should I set this to 5 instead of 1 (default)

Thank you

[Simonr]

Hi

The peripherals will only connect to one central at a time, right? If so you will not need to increase this number on the peripheral side, as only the central device will handle 5 different connections. The peripheral will not know/care about the others that the central is connected to.

Best regards,

Simon

[masterLee]

The five peripherals connect to one specific central device (windows desktop with BLE 5.0 adapter).

The peripherals firmware is based on the ble_app_uart example for nRF52840 of the nRF SDK

The reason I created the post is because I cannot receive the same amount of data from all five devices (all devices have the same firmware)  and I try to figure out what I am doing wrong. I have changed the connection interval and connection event length many times without progress yet. 

For example, in the last configuration I set the Connection Interval: 37.5 - 50 msec and connection event length: 7.5msec  to all five peripherals and started sending raw data to the central for one hour.  When the test completes, a results file is created by the PC app where I can see how many bytes have been received by the central and how many have been lost.

Device	Received packets	Lost Packets
1	14744	0
2	5700	9049
3	4892	9645
4	5416	9078
5	5792	8762

The pattern is not always the same by means of the number of devices that lose packets,

which devices lose packets and how many packets are lost each time. It is rather random.

Any ideas?

Thank you

   

[Simonr]

Hi

This sounds like an issue with the central not able to keep track of all the peripherals here. Have you tried increasing the connection event length so the central has more time with each peripheral device? Are you able to take a sniffer trace so we can see what happens over the air here, either with the nRF Sniffer or using a dedicated Bluetooth sniffer? How does the PC handle the connections on your end? It seems strange that the first device have no packets lost while the other seem rather similar in losing ~two thirds of the packets.

Best regards,

Simon

[masterLee]

HI,

Yes, I will increase the connection event length first thing today and I will come back

Also, yes I have used the sniffer in the past with wireShark so if the issue will persist I try the sniffer.