BLE scan timeout always in multiple of second

[guohui]

Hi there,

I'm developing applications with nRF52840, SoftDevice 6.1.1. Normally the scan timeout is in step of 10 ms. But whichever the value I set between seconds, e.g., 500ms, 1500ms, the actual scan timeout is 1 seconds, 2 seconds and etc.

This is the code snippet:

LOG_DEBUG(TRACE, "| interval(ms)   window(ms)   timeout(ms) |");
LOG_DEBUG(TRACE, "  %.3f        %.3f      %d", bleGapScanParams.interval*0.625, bleGapScanParams.window*0.625, bleGapScanParams.timeout*10);
int ret = sd_ble_gap_scan_start(&bleGapScanParams, &bleScanData_);


  

This is the log with timestamp:

    0000000435 TRACE:   interval(ms)   window(ms)   timeout(ms)

    0000000445 TRACE:   5.000             2.500             300

    0000001446 TRACE:   BLE GAP event: Scanning timeout (This is printed in the SoftDevice events interrupt handler)

Any hint would be really appreciated!

[Einar Thorsrud]

Hi,

This is not a limitation of the SoftDevice (BLE stack), so I think we need to see more of your code. It could be for instance that you are doing some integer math that causes this, but that is just a guess without seeing what you are doing.

[guohui]

More code can be found here: https://github.com/particle-iot/device-os/blob/fix/ble/v1.3.1-rc.1/hal/src/nRF52840/ble_hal.cpp#L1230

Thank you so much!

[Einar Thorsrud]

Hi,

This is odd. I don't see anything that should cause the timeout to be in whole seconds. How have you verified that scanning is in whole seconds? In other words: How do you check how long time the device scans?

[guohui]

By measuring the power consumption during scanning, from the current chart I captured, the scan interval and scan window did align with the value that I set in my application, while the timeout always in multiple of second.

[Einar Thorsrud]

Hi,

I see. Can you compare it with when you get the timeout event from the SoftDevice? Does that happen after a whole second as well?