nrf52832 ble-hids-keyboard -measure the bluetooth report rate

[jayden123]

I want to measure the Bluetooth report rate. Is there a way to do it?

Or let me know if you have any information on the basic nrf52832ble response speed.

[Edvin]

Hello,

I am not completely sure what you mean. We have samples that can test the throughput, and you can create samples that can test the back and forth latency (by replying to a message, and timing the time it takes from you send until you get a reply). But none of these are trivial to test in the ble-hids-keyboard sample, since you can't send as much data as you like (only keyboard data), and you can't get the computer to reply back.

Also, the response speed heavily depends on the connection parameters (connection interval). The shortest possible is 7.5ms. Whenever you send a message, it will be sent in the next connection event (which occurs every connection interval). For BLE lkeyboards the connection interval is typically 7.5ms.

[jayden123]

Is there any data that can refer to the BLE response speed? I need evidence to prove it.

[Edvin]

What exactly do you need to prove?

[jayden123]

I want to measure the Bluetooth response time.

[Edvin]

I assume you are still talking about a keyboard. How would you normally measure the response time of a keyboard (a wired keyboard, not bluetooth)?

There is no trivial way to do this. Either you need to write your own software that connects to your peripheral-hids-keyboard that can receive the keystroke and signal this on a pin, or you can set up a high speed camera to measure the latency between a keypress and the received press from the computer. Something like this. 

The reason this is not trivial is that there is no event in the keyboard application telling you when the message was sent to the computer. It is possible to get a callback on the nRF when this message was sent. You can look at how this project uses bt_hids_inp_rep_send() in main.c -> key_report_con_send(). The last input parameter here is a callback to when the message is sent, but I don't know the accuracy of the timing of this event. It is used to know when the message was acked by the receiver, and that your buffer is free to be reused if needed.

Best regards,

Edvin