Multilink Central Example does not work with high connection intervals

RE: Multilink Central Example does not work with high connection intervals

muhkuhns — Tue, 19 May 2015 14:48:10 GMT

I see. Great post! Thank you! But you also just mention advertising interval and scan interval/window. But also if I only change min/max connection interval from 500/500 to 4000/4000 the time it takes for the first measurement to show up increases from ~15seconds to slightly over 2 minutes. And this is what I can't explain by myself. I just went home now and left my setup at the university. I will play around with the values again tomorrow to see what I can achieve.

Advertising intervall 20ms and 
#define SCAN_INTERVAL                    0x0029
#define SCAN_WINDOW                      0x0028

shouldn*t this connect in no time? still takesmore than 20seconds after the central starts scanning

RE: Multilink Central Example does not work with high connection intervals

MartinBL — Tue, 19 May 2015 14:43:02 GMT

I updated my answer above.

RE: Multilink Central Example does not work with high connection intervals

muhkuhns — Tue, 19 May 2015 13:41:03 GMT

Yeah sorry, I had something checkd in the search tab by mistake but found it just one second later. I'm a bit exhausted already. If I am not mistaken, it just started working now after some time!

Yeah it takes some time, as you mentioned in your original answer. But it works! Gonna try lower PPM settings now and see what is the lowest that works. Thank you so much so far! Looks like it starts working with >=100 PPM

(How) Can I speed up the initial connection process? Or in other words: Why does it take so long for the first measurement compared to lower connection intervals?

RE: Multilink Central Example does not work with high connection intervals

MartinBL — Tue, 19 May 2015 13:35:21 GMT

Just search for 'SOFTDEVICE_HANDLER_INIT' in main.c and change

SOFTDEVICE_HANDLER_INIT(NRF_CLOCK_LFCLKSRC_XTAL_20_PPM, false);

SOFTDEVICE_HANDLER_INIT(NRF_CLOCK_LFCLKSRC_XTAL_500_PPM, false);

RE: Multilink Central Example does not work with high connection intervals

muhkuhns — Tue, 19 May 2015 13:32:12 GMT

Yeah, I also found this topic, but the devices are lying next to each other on my table. And it does work perfectly with lower intervals. I tried it with the 500PPM settings. Still doesn*t seem to work :/

RE: Multilink Central Example does not work with high connection intervals

MartinBL — Tue, 19 May 2015 13:26:14 GMT

Error 0x0008 corresponds to BLE_HCI_CONNECTION_TIMEOUT. Some people experience this when their device goes out of range.

Another possible solution might be timing issues caused by poor accuracy on the low frequency 32,768Hz crystal on the Seeed BLE Micro. According to the Seeed BLE Micro schematic there is a crystal, but it doesn't say anything about the accuracy. Try to increase the ppm value in SOFTDEVICE_HANDLER_INIT();. Try the largest value first: NRF_CLOCK_LFCLKSRC_XTAL_500_PPM.

RE: Multilink Central Example does not work with high connection intervals

muhkuhns — Tue, 19 May 2015 09:51:54 GMT

This is #1 on my schedule for today when I finally finished running around looking for a pressure-tight case. I will update this.

Tested. Does not work. Please see edited questions for logfiles.

RE: Multilink Central Example does not work with high connection intervals

MartinBL — Tue, 19 May 2015 09:10:29 GMT

Have you tried to run the example codes "as is", without your own code? And then use the parameters you mention above? It would be a quick way to see if your problem lies in your own application. I'm afraid the code you attached is too extensive for me to test or go through. Are you also able to debug your code and see if you get any asserts?

RE: Multilink Central Example does not work with high connection intervals

muhkuhns — Wed, 13 May 2015 13:51:04 GMT

Thanks for your answer! But too bad they don't work for me, and I don't know what I could've changed that could cause this.. :( Oh. And of course I am using v2.0.0 my Bad... I waited up to 5 minutes and nothing happened. But why does connection interval influences the time they need to connect anyway? Shouldn't only advertising and scanning affect this?

I tested it now again for 10 Minutes with the following settings:

Peripheral: advinterval:500, min/max conn:2000/4000 timeout 8100
Central: scanning interval/window A0/50 min/max/timeout as above.

As far as my RTT Output goes the central starts scanning but then nothing more is happening.. If I change the centrals min/max conn. to e.g. 200/400 it connects and enables notifications in a few seconds.

RE: Multilink Central Example does not work with high connection intervals

MartinBL — Wed, 13 May 2015 13:43:34 GMT

Hi,

Error 0x0008 corresponds to BLE_HCI_CONNECTION_TIMEOUT. A common source for this error is timing issues caused by poor accuracy on the low frequency 32,768Hz crystal. According to the Seeed BLE Micro schematic there is an external crystal, but it doesn't say anything about the accuracy. Try to increase the ppm value in SOFTDEVICE_HANDLER_INIT() called in main.c. Try the largest value first: NRF_CLOCK_LFCLKSRC_XTAL_500_PPM.

Here is a great thread explaining a bit about various low frequency clock sources.

The reasons why I suspect a timing issue is that your values work fine on my own development kits from Nordic (with known clock accuracies). It just takes a long time for the devices to connect (a few seconds to a couple of minutes). On the peripheral side I have a PCA10001 kit with S110 V7.1 and SDK V6.1. On the central side I have a nRF51 Dongle (also tried DK) with S120 V2.0.0 and SDK V8.1 (also tried V8.0).

To understand why it takes so long for your two devices to connect you can have a look at this thread. Your advertise interval is pretty high and your scan interval/window pretty low. Hence it will take a while before the peripheral is advertising and the central is listening at the same time (To make absolutely sure that the windows and intervals eventually overlap a small random delay is added to the advertisement interval).

Here is a little more info about intervals etc.

To speed up the connection time you can experiment with decreasing the adv interval or maybe also increase the scan interval and/or window. However this will draw power, as you know. In the end you will have to compromise. If you plan to stay most of the time advertising then maybe a long adv interval is best. If you, on the other hand, stay connected most of the time you can have short adv intervals and long connection intervals.