Very low throughput iOS8.1 and nRF51822

RE: Very low throughput iOS8.1 and nRF51822

Vyacheslav Lebets — Fri, 02 Oct 2015 19:26:07 GMT

Sorry, Hung, but in said section are given certain rules when using Sequential Protocol and nothing is said about what it should be in the connection interval. As my mind, I think that several request-response pairs can occur in one connection interval.

RE: Very low throughput iOS8.1 and nRF51822

Vyacheslav Lebets — Fri, 02 Oct 2015 11:47:41 GMT

Ok, Thanks!

RE: Very low throughput iOS8.1 and nRF51822

Hung Bui — Fri, 02 Oct 2015 11:45:46 GMT

Yes, you can have a look at section 3.3.2 part F Vol 3 in the Bluetooth Core spec v4.2

RE: Very low throughput iOS8.1 and nRF51822

Vyacheslav Lebets — Fri, 02 Oct 2015 11:04:12 GMT

Hi, Hung. Thanks for responce! I did not know that to do only one request/indication at a connection interval. Is this exist in Bluetooth specification?

Well, now I will try... :)

Thanks!

RE: Very low throughput iOS8.1 and nRF51822

Hung Bui — Fri, 02 Oct 2015 10:38:51 GMT

Hi Vyacheslav,

From the sniffer trace we can see that you are using Write request (from the master side) and indication (from the slave side) to send data. If you want high throughput, this is not a good idea.

By spec, there will be only one request/indication at a time. Only when the request got response or the indication got confirmation the next one can be sent.

This explains why you got low throughput. You should use write command and notification instead. Please have a look here.

RE: Very low throughput iOS8.1 and nRF51822

Vyacheslav Lebets — Thu, 01 Oct 2015 20:19:47 GMT

It makes no difference.

RE: Very low throughput iOS8.1 and nRF51822

kirkus — Thu, 01 Oct 2015 20:02:28 GMT

Try setting your min and max connection interval settings to conform to Apple's Bluetooth Guidelines (developer.apple.com/.../BluetoothDesignGuidelines.pdf):

Interval Max * (Slave Latency + 1) ≤ 2 seconds
Interval Min >= 20ms
Interval Min + 20 ms ≤ Interval Max Slave Latency ≤ 4
connSupervisionTimeout ≤ 6 seconds
Interval Max * (Slave Latency + 1) * 3 < connSupervisionTimeout

For example:

#define MIN_CONN_INTERVAL MSEC_TO_UNITS(20, UNIT_1_25_MS)
#define MAX_CONN_INTERVAL MSEC_TO_UNITS(30, UNIT_1_25_MS)
#define SLAVE_LATENCY 0
#define CONN_SUP_TIMEOUT MSEC_TO_UNITS(6000, UNIT_10_MS)

See if that makes a difference.

RE: Very low throughput iOS8.1 and nRF51822

Wojtek — Thu, 01 Oct 2015 12:27:03 GMT

Try using write without response and notification instead of indication.

RE: Very low throughput iOS8.1 and nRF51822

Vyacheslav Lebets — Thu, 01 Oct 2015 11:43:49 GMT

nRF - is peripheral, i use s110 v7.0.0. booth devises can transmit up to 128 bytes (with chunk = 20 bytes), and on nRF side i have buffer fo placing received data up to 128 byte. But there is no difference if I pass one packet (20 byte) or more, always packet is transmitted approximately 30 ms from write_with_responce to confirm (in ios) and from indication to confirm (in nRF).

RE: Very low throughput iOS8.1 and nRF51822

Wojtek — Thu, 01 Oct 2015 11:23:53 GMT

Ok - what softdevice are are you using? nrf51822 is peripheral or central? which device has to transmit that large packet, both? I don't know ios, but on the nrf51 side: do you fill tx buffers until you get error? I haven't tested receiving with high throughput with nordic, but I have no problems to transmit (notifications, not indications!) 6 packets/connection interval to Master Control Panel app, and 4 packets/interval to my i9505. Device which is receiving (in your case iphone4s) may be limiting that. S110 specification says that it is possible to receive write commands with 125kbps which means 6packets/interval, but write requests only 10kbps

RE: Very low throughput iOS8.1 and nRF51822

Vyacheslav Lebets — Thu, 01 Oct 2015 11:13:58 GMT

Ok, but in connection interval ios may send 6 packet and nordic 4 packets? why only ONE packet transmitted?

RE: Very low throughput iOS8.1 and nRF51822

Wojtek — Thu, 01 Oct 2015 11:06:29 GMT

You can sniff CONN_REQ packet when initializing connection and you will probably see that connection is established at 30ms connection interval (or slave requests connection parameter update to make it 30ms...). Anyway - it is probably because connection interval that is used between your devices.