RE: 51822 RF setting Problem

Håkon Alseth — Wed, 25 Jun 2014 11:37:02 GMT

I will recommend that you try my comments for Q3 first before altering any other gazell configurations.

Q1. Most likely it's because you're losing sync. I would recommend that you scope the VDD_PA pin on your device, and post the results here. This pin will go high for each TX on-air operation, and will give you a good overview if the sync is off.

Q2. This function sets the number of timeslots that the device considers itself to be in sync with the host after a successful transfer. In your case, if you set this to 10, it will consider itself in sync for 10 x timeslot (with no successful communication) before the link is not-in-sync. If after 9 timeslots you receive an ACK from the host, the link will be considered in-sync for the whole process.

This means that you can get one packet through every 9 timeslots (9 ms in your case), giving a throughput of 3.5 kBps, and your link is considered in sync for the whole period.

Try these settings. Host:

#define GZLL_DEFAULT_PARAM_RX_CHANNEL_HOLD_PERIODS 5

Device:

nrf_gzll_set_device_channel_selection_policy(NRF_GZLL_DEVICE_CHANNEL_SELECTION_POLICY_USE_SUCCESSFUL);

This will cause your link to be asynchronous, but it will force the host to not switch RF channel for 10 ms if it receives a packet. The device will then start communication on the last successful RF channel. This will be a "frequency agility" approach, where the host and device only changes RF channel when the re-transmission count is high.

This approach is not very good if you have other devices that needs consistent data transfer, as it disrupts the host listening pattern.

Q3: This will cause the external 16M to be stopped/started by the gazell library. Note that it takes up to 1.5 ms for a 16M xtal to start up (nom. 800 - 1000 us on most xtals). I would recommend that you set this to NRF_GZLL_XOSC_CTL_MANUAL, and start the xtal manually before enabling the gazell library:

// Start 16 MHz crystal oscillator.
NRF_CLOCK->EVENTS_HFCLKSTARTED = 0;
NRF_CLOCK->TASKS_HFCLKSTART    = 1;

// Wait for the external oscillator to start up.
while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) 
{
    // Do nothing.
}