8mA current draw with timeslot API, BLE + Gazell host, softdevice 130

RE: 8mA current draw with timeslot API, BLE + Gazell host, softdevice 130

ovrebekk — Tue, 12 Mar 2019 09:12:19 GMT

Good to hear you found a solution. If you only have Nordic devices in your system then skipping BLE altogether is often the best solution in terms flexibility and code size.

RE: 8mA current draw with timeslot API, BLE + Gazell host, softdevice 130

Spok — Tue, 12 Mar 2019 08:09:16 GMT

Thanks,

I fiddled a bit with BLE as Peripheral + Central, but in the end I used 2 nrf51822 as devices, and 1 as receiver, without using BLE.

RE: 8mA current draw with timeslot API, BLE + Gazell host, softdevice 130

ovrebekk — Tue, 12 Mar 2019 07:43:07 GMT

Sorry for the slow response. I forgot to include the verified cases in my active list.

The S110 uses less flash, so you have more available to your application. Other than that there is no reason why you can't use the S130 for a peripheral only device.

Most of the BLE peripheral examples in the SDK show you how you can use either the S110 or the S130 to make a connection to a central device.

Best regards
Torbjørn

RE: 8mA current draw with timeslot API, BLE + Gazell host, softdevice 130

Spok — Mon, 14 Jan 2019 15:13:07 GMT

Hi,

Thanks for your reply, this is very interesting indeed.

Would you have a link to a sample project for running S110 and connecting with BLE to a central link ?

Edit: I have started looking into it, and I am not sure why s110 is better suited as BLE peripheral than s130.

I am marking your answer as "verified" since you answered my original question.

RE: 8mA current draw with timeslot API, BLE + Gazell host, softdevice 130

ovrebekk — Mon, 14 Jan 2019 14:51:45 GMT

The Gazell protocol is optimized for the peripheral to dongle scenario where you have low power peripherals like keyboards and mice talking to a USB dongle with ample power available. As such it is correct that the host will always keep the receiver on, to make sure the device can reach it as quickly as possible.

Have you considered using BLE rather than Gazell for the communication between the two halves?

If you run the S130 SoftDevice on one of the halves it can set up one link as a peripheral and one as a central at the same time, and you can run the S110 SoftDevice in the other half to connect to the central link of the first.

You might have to give up a bit of flash memory, but you should get a more power optimized solution.

Best regards
Torbjørn

RE: 8mA current draw with timeslot API (BLE + Gazell) softdevice 130

Spok — Sun, 13 Jan 2019 15:36:28 GMT

Actually, now that I think of it, could it be that a gazell host will always draw this much current. Looking back at the specification, I see that gazell devices should be very power efficient, but I cannot find current consumption figures for the gazell host.

It is ok for me to put a bigger battery in it, but I would like to make sure that I am not missing something obvious first.

RE: 8mA current draw with BLE + gazell

Spok — Sat, 12 Jan 2019 21:39:52 GMT

One more discovery : if I try to lower the length of the timeslot (from 10 000 us to 5 000 us), my power consumption goes way down (to about 3.5 to 4.5 mA). But the reliability of the connection between the halves too.

Here is my timeslot configuration

 m_slot_length = 5000;                                                        
 m_timeslot_request.request_type = NRF_RADIO_REQ_TYPE_EARLIEST;               
 m_timeslot_request.params.earliest.hfclk = NRF_RADIO_HFCLK_CFG_NO_GUARANTEE; 
 m_timeslot_request.params.earliest.priority = NRF_RADIO_PRIORITY_NORMAL;     
 m_timeslot_request.params.earliest.length_us = m_slot_length;                
 m_timeslot_request.params.earliest.timeout_us = 100000;