Apple Watch BLE APP can not connect nRF52810

[Yinbun Ye]

Hi, 

I am using the sdk 17.0.2 and s112.

The Apple Watch can not connect the s112 projects ble, such as 10040e s112 and 10040 s112, But can connect the 10040 s132 ble.RTT log had indicated the connect is complete, but Wireshark show differentwatch 52810.pcapngwatch 52832 132.pcapngwatch et05 112.pcapng

[Kenneth]

The only real difference I can find is related to data length extension, this is not supported on the s112 softdevice (see difference in LL_FEATURE_RSP packet). I can find in the Apple Bluetooth guidelines recommend this should be supported: 
https://developer.apple.com/accessories/Accessory-Design-Guidelines.pdf

"Accessories should support Data Packet Length Extension for best performance with devices."

So it could be that this is a requirement for apple watch, though it is not stated directly.

Kenneth

[Simon]

Hello,

this is interesting,
which app can be used on an Apple Watch to perform this test?,
something like an nRF Connect for the Watch

but I'm not understanding how data length extension is not supported in s112,
if in sdk_config.h when you can change NRF_SDH_BLE_GAP_DATA_LENGTH from 27 to 251,
and then not have s112 complain when connecting or running NUS routines.
Or is this not the same data length as to what Apple is reffering too?
Or does s112 totally ignore that setting even if it still shows up in the pca10040e examples.

thank-you,

[Kenneth]

The DLE parameters are not used by S112 softdevice no, I believe there is check at compile time that check which softdevice is used.  It could be interesting to try the S113 softdevice, since S113 is really an S112+DLE. Though it is about 12kB larger I believe due to the implementation of DLE.

Best regards,
Kenneth

[Simon]

I tried apps Bluefruit Connect & Bluetooth Terminal for Apple Watch,
but it seems both are just relays from the peripheral (DK52) to iPhone,
and then relay from iPhone to Watch, not DK to Watch directly.
Testing with SDK 17.0.2, UART example, all three S112, S113 (added) and S132 will connect.
So now not sure what app Yinbun Ye was using on the Watch to test S112 directly.

Also,
I checked the size of S112 compared to S113 (7.2.0) in Programmer,
and in the file memory layout, the sizes were:
S112 - 98284 bytes
S113 - 107692 bytes
a difference of 9408 bytes, somewhat smaller than 12kB according to Programmer.