Re: #nrf52840 #ble unstable connection #ble #nrf52840

Chettimada, Vinayak Kariappa

Hi Randy,

Could you please let us know the LF clock src used in your EVB?

If you are using 32KHz external crystal as source (CONFIG_CLOCK_CONTROL_NRF5_K32SRC_XTAL=y),
and the accuracy is not the default 20 ppm (CONFIG_CLOCK_CONTROL_NRF5_K32SRC_20PPM=y),
please select the correct one, i.e. if 250 ppm then CONFIG_CLOCK_CONTROL_NRF5_K32SRC_250PPM=y.

If you are using built-in 32KHz RC oscillator as source (CONFIG_CLOCK_CONTROL_NRF5_K32SRC_RC=y),
then please use CONFIG_CLOCK_CONTROL_NRF5_K32SRC_500PPM=y.

Do send us your application generated .config file, in case you want me to check what is configured in comparison to the source and actual accuracy of the clock source in your EVB.


-----Original Message-----
From: <devel@...> on behalf of Randy Chou <rchou3@...>
Date: Thursday, 1 November 2018 at 4:03 AM
To: "devel@..." <devel@...>
Subject: [Zephyr-devel] #nrf52840 #ble unstable connection

Hi community,
I'm using nrf52840 on our own development board, I met one problem about abnormal disconnect.

* environment:

[Central] use BLE nRF connect run on nRF52840_PCA10056 (Windows)
[Peripheral 1] Zephyr peripheral_hids sample application runs on nRF52840_PCA10056
[Peripheral 2] Zephyr peripheral_hids sample application runs on our EVB (nRF52840)

* result:

[per 1] the connection keeps.
[per 2] abnormal disconnect while I move the central a bit far away from peripheral (< 1m).

* experiment

1. move the central device close next to peripheral 2. it can keeps connection.

2. change the connection interval from 30ms to 7.5ms/10ms/15ms, it can keeps connection

3. use our own FW which uses SoftDevice as Bluetooth stack. The distance won't affect the connection.

I'm wondering is this issue related to frequency drift.
As my understanding, in SoftDevice, it will do the clock calibration automatically.
I only find one related configuration (CONFIG_CLOCK_CONTROL_NRF5_K32SRC_250PPM).
Does it also have same feature in Zephyr?
or do you have other comment about this issue?


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