Low Throughput Issues

RE: Low Throughput Issues

willdavies — Fri, 03 May 2019 02:13:52 GMT

I was able to resolve the issue, thanks for the help!

Changed connection interval to 400 ms and event length to:

#define NRF_SDH_BLE_GAP_EVENT_LENGTH 400

RE: Low Throughput Issues

willdavies — Thu, 02 May 2019 20:27:14 GMT

The Android device is actually reporting the interval:

D/BluetoothGatt: onConnectionUpdated() - Device=FC:88:C7:C9:5C:82 interval=9 latency=0 timeout=400 status=0

The interval is 9 ms, so it seems like something else might be causing the issue.

RE: Low Throughput Issues

haakonsh — Thu, 02 May 2019 08:46:06 GMT

There's a difference between what parameters you tell the SoftDevice that you would like to get and what the actual outcome of the negotiations between the Link Layers are. You need to verify those parameters, I suggest you set up a sniffer (nRF Sniffer User Guide v2.1) to see what the negotiated parameters are.

My guess is that you get a 100ms connection interval because the android stack does not support 7.5ms and you have not given it any other option but 7.5ms.

See Data Length Update Procedure and GATTC ATT_MTU Exchange for examples.

RE: Low Throughput Issues

willdavies — Tue, 30 Apr 2019 21:10:22 GMT

The Android device reports MTU length 247 and I receive packets of length 244 (data payload). The connection interval is defined as 7.5 min, 7.5 max when setting up the connection. I'm not sure how to read these values on the chip to see if they were successfully setup.

RE: Low Throughput Issues

haakonsh — Tue, 30 Apr 2019 08:23:14 GMT

And what Connection interval, MTU length, Data length extension, and Connection event length are you getting?

RE: Low Throughput Issues

willdavies — Tue, 30 Apr 2019 03:45:47 GMT

As far as I know, the Android device successfully connects with the connection interval as 7.5 min, 7.5 max.

The Android device receives a MTU update of 247, and a PHY update of rx=2, tx=2 as well.

I currently call the following function to enable event length extension: https://github.com/wdavies973/MagiCoil-microcode/blob/943c757fee94b1141a1ee2b6c8374bcdf40c6453/main.c#L642

I do also receive data packets of length 244 on the Android device.

RE: Low Throughput Issues

haakonsh — Mon, 29 Apr 2019 09:04:25 GMT

"Connection interval: 7.5 min, 7.5 max" As far as i know the Android BLE controller does not support a lower Connection Interval than 15ms, but I've not seen the spec for the galaxy 9.

Have you enabled Connection Event Length Extension?

We need a sniffer trace of the connection establishment and connection parameter negotiation.