about nrf51 Gazell timeslot period

[OPQ]

hi, I test the gazell example gzll_ack_payload in SDK9.0,I found that the default timeslot period is 600us.But after testing using logic analysis,I found sometime transfer interval is600us,but most time it's 1200us. What's the reason?

[Sigurd]

Hi,

Gazell can only send a new payload every 2 timeslots. So the transfer interval will be 1200us, resulting in a maximum data rate of 213 kbps in each direction.

The reason for this is the way the Gazell device synchronizes with the host. The host will stay on each frequency for 2 timeslot periods. When the device gets an ACK from the host it know that it is synchronized to the host, but it doesn't know whether the host is on the first or second timeslot for that specific channel. The only way the device can be sure that it will stay synchronized with the host is to update the RF frequency and add a new payload on every other timeslot, at the same rate that the host is changing frequency.

[OPQ]

Hi Siguard, Thanks. So,the some 600us transfer interval is the retransmision?

[OPQ]

I test the VDD_PA pin.

[Sigurd]

Yes, that is correct.