Synchronization of two placed closed nRF52840

RE: Synchronization of two placed closed nRF52840

Ars Morozov — Tue, 09 Jul 2019 15:29:43 GMT

[quote userid="6462" url="~/f/nordic-q-a/49460/synchronization-of-two-placed-closed-nrf52840/197200"]Why do all the connections have to be simultaneous?[/quote]

It's very good idea to use some more smart connection managment, instead of simple connection.

RE: Synchronization of two placed closed nRF52840

awneil — Mon, 08 Jul 2019 15:55:39 GMT

Why do all the connections have to be simultaneous?

Couldn't you devise some scheme to schedule your connections so you only need (no more than) 20 at once ... ?

Or perhaps the nRF52840 is just the wrong part for your requirement?

The nRF52840 is really targetted at small embedded systems - have you looked for stuff targetting larger "host" systems ... ?

RE: Synchronization of two placed closed nRF52840

Dmitry — Mon, 08 Jul 2019 14:52:16 GMT

You can change channel map with sd_ble_gap_opt_set(BLE_GAP_OPT_CH_MAP). Maybe it's not optimal idea to split by even-odd channels, but group them, for example, by 5 - just ensure that some wideband source of interference, like wifi AP, will not cover one of your boards entirely.

[quote userid="67850" url="~/f/nordic-q-a/49460/synchronization-of-two-placed-closed-nrf52840/197012"]Why? Softdevice use App Timer (as I know), is it impossible to synchronize it?[/quote]

Softdevice resources (including RTC0) are protected and cannot be accessed directly from your code, only via SoftDevice API. With API, you have control only over connection interval and channel map, there are no methods to force a connection event at distinct time.

RE: Synchronization of two placed closed nRF52840

Ars Morozov — Mon, 08 Jul 2019 08:00:37 GMT

Hi, thanks for the answer.
It's really interesting way, but it seems to me that there will be too much noise from second chip will be on the first one even if it uses different (but close!) channels. Anyway, how can I control channels by soft? (I mean which libraries, functions ..)

[quote userid="5418" url="~/f/nordic-q-a/49460/synchronization-of-two-placed-closed-nrf52840/196968"]You cannot control internal timings of SoftDevice.[/quote]

Why? Softdevice use App Timer (as I know), is it impossible to synchronize it?

RE: Synchronization of two placed closed nRF52840

Dmitry — Sun, 07 Jul 2019 16:28:48 GMT

Hi,

I think it's too complex task to go this way at all - think about crystal frequency deviation, you will see up to 80 usec shift between boards every second. You cannot control internal timings of SoftDevice. A much simpler way is to split BLE frequency range into two halves with channel maps - for example, odd channels for first board, even channels for second one.