packets Loss in nRF51 & iOS streaming.

[Bayram ZAYET]

Hello NORDIC community,

I am performing a BLE throughput speed test via an example of streaming a buffer of 2500 bytes per second: This says a sending frequency of 19 Kbps.

I'm working on an iPhone 6s with a version of iOS: 10.3.2 Since the connection interval is 30ms (the minimum value supported by an iPhone). The sending and receiving frequency is 31 Kbps: for the value of 6 packets per connection interval. this stream should be working fine.

==> the result of my tests shows considerable losses !!!

I wanted to know if my problem results from my module nRF51 or the iPhone?

Am I missing a parameter in my calculations ?

If possible, is the number of packets per connection interval on an iPhone 6s with an iOS: 10.3.2 really 6 or less?

Thank you in advance for your reactivity.

Best Regards,

[Bayram ZAYET]

The transfer is from nRF51 to iOS. I am suspecting iOS application because I got no loss using MCP as a master. I my implementation: I am checking on HVX return and TX_COMPLETE:

void stream(void)

{

while(1)

{ err_code = ble_send(&m_service, data); if(err_code != NRF_SUCCESS) { break; } } }

ble_send() function contains the HVX call.

	case BLE_EVT_TX_COMPLETE:
					stream();												
                   break;

[run_ar]

What iOS app are you testing with? are you sure you handle all the peripheral:didUpdateValueForCharacteristic:error: callbacks?

[Bayram ZAYET]

I was testing with LightBlue iOS application and I got packets loss.

But assuming that the connection interval isn't the problem, can I be sure that iOS packets per connection interval reaches 6 packets? Isn't it limited to 4 or 3 ?

Many thanks.

[run_ar]

There is no hard limit with iOS, i.e. you can send a lot of packets in each event. Anyway I'm not sure what happens in lightblue. So you have to check with a ble sniffer to see if you are loosing packets or not. If you follow the flow you describe on the nrf5, I guess it might be an issue with displaying received content in lightblue. Remeber that a notification will be retransmitted until it is received by the peer or until the connection is lost. So it is not possible to loose packets unless the receiving side overwrites it's RX buffers, or the application does not handle the packets correctly.