Time synchronization with alternating masters

Question

Dear members,

with success I implemented the time synchronization example from the nRF5 SDK guide.
This example works perfect for a single master, but what if the master changes?
When I check my scope it will show that the new master starts sending the sync beacons, but the slave (previous master) is not receiving and stays low.
Would there be a solution to put a master in receiver mode after stopping the sync beacons?

I am using four nRF52840-DKs with Segger Studio, SDK 17 and a S140 softdevice (used for a custom BLE service)

user2167 · Accepted Answer

No problem! I think I was looking at a different branch than you. 
 In the master branch, the equivalent of "m_master_counter_diff" is "m_master_counter". These variables keeps track of the transmitter/master counter value. This is normally 0 on the transmitter side, except for when a device used to be a receiver and switches to be a transmitter. 
 If this value is not the same on transmitter and receiver, and you set a trigger using ts_set_trigger (), the triggering time might be in the past, or far in the future. 
 When changing from receiver to transmitter mode, you can either reset the m_master_counter variable (which would cause a potentially large leap in the timing), or take it into account here as a transmitter: https://github.com/nordic-auko/nRF5-ble-timesync-demo/blob/master/nRF5_SDK_16.0.0_98a08e2/examples/common/time_sync.c#L544 You can try to reset the variable first and see if this works? 
 Best regards, 
 Audun

Time synchronization with alternating masters

Top Replies