Wireless Communication Synchronization System

[Shinya Sakaida]

I used Nordic's proprietary protocol ESB to develop a system that can synchronize multiple radios equipped with nRF51822 or nRF52832.

The outline of the development system is as follows. I'll introduce you.

Of the multiple radios in this system, one radio transmits a synchronization request signal and held data to the other radios at regular intervals.
Other radios receive the synchronization request signal and data mentioned above at intervals that are integral multiples of the fixed time mentioned above.
As a result, each of the above-mentioned radios periodically establishes synchronization with the above-mentioned one radio and receives the above-mentioned data.
Each wireless device that has established synchronization further transmits its own data and a synchronization request signal to other wireless devices other than itself at fixed intervals as described above.

By performing this operation on all radios in the system, all radios can be synchronized and data can be shared between each radio.

This operation is performed without distinguishing between the base unit and slave units, and there is no need to identify each radio unit by address, etc.

By transmitting and receiving a synchronization request signal between each radio, the difference in reception operation start timing due to the difference in the operation reference clock between each radio is cleared, and the timing deviation due to the accumulation of the clock difference does not occur.

Since each wireless device can synchronize wireless transmission and reception, intermittent transmission and reception is possible, and low power consumption of the system is realized.

Synchronization is achieved in each radio period, so synchronous lighting of LEDs and synchronous illumination with RGB LEDs can be realized wirelessly.

By connecting a sensor to each radio, a sensor network may be realized.

If you have any uses for this system, we would appreciate it if you could suggest them.

[D_Crow]

Hi Shinya,

Nice idea for a synced system, have you tested it to see what synchronisation accuracy can be achieved? The system described by a Nordic employee here has a 65 ns jitter between wirelessly synced timers at a 100 Hz transmit rate but is quite power hungry. 

[Shinya Sakaida]

Dear  D_Crow

We would like to introduce an example of the Wireless Communication Synchronization System that we developed.
The above Wireless Communication Synchronization System is a system in which LEDs mounted on multiple wireless devices emit light synchronously.

Sends synchronization request signal and data every 250ms.
The synchronization request signal and data are received every 30 seconds, which is 120 times 250ms.
The CPU is normally in a sleep state and becomes active only when transmitting and receiving synchronization request signals and data.
When receiving, it wakes up from sleep just before the timing of transmission from another radio, and goes back to sleep after receiving.
It sleeps when not transmitting or receiving to reduce power consumption.
Power consumption is less than 3V 200uA, excluding LED lighting current.
The LED is switched on and off at the timing of waking up from sleep every 250ms.
The synchronization difference between multiple radios is 0 to 30ms.
In the above system that switches the LED ON and OFF every 250 ms when waking up from sleep, there is a maximum 30 ms lag in synchronized light emission, but this lag is invisible to the human eye.

Best regards