Coexist example does not connect iPhone

[leejh]

Hello, Nordic.

I'm configuring a mesh network. The provisioner, client and server all going well, except for one problem.

I made a client and server based on sdk-coexist, a basic example provided by Nordic. But I can't connect to BLE NUS on iPhoneX, iPhone13.

The enviroment and problems are as follows:

 - current using   : S.E.S Tool / SDK v16.0 / MeshSDK v4.2

 - Testing mobile : iPhone 6 [O] / iPhone 6+ [O] / iPhone X [X] / iPhone 13 [X]

 - problems log

<info> app: Connected
<info> app: Data len is set to 0x42(66)
<error> nrf_ble_gatt: sd_ble_gap_data_length_update() (request) on connection 0x0 returned NRF_ERROR_RESOURCES.
<error> nrf_ble_gatt: The requested TX/RX packet length is too long by 178/178 octets.
<info> app: Disconnected

The iPhone 6, iPhone 6+ and Android Phone are shown same log, but Connection / NUS working well.

But, iPhone X and iPhone 13 cannot connect after the log above (checked in nRF Connect and nRF Toolbox)

I have tested as follow

I will waiting for your reply. thanks

[Mttrinh]

Hi,

Just to clarify, you tested as mentioned in the picture for all of the phones mentioned and only iPhone X and iPhone 13 couldn't connect to the device?

I made a client and server based on sdk-coexist, a basic example provided by Nordic

Is this a custom application based on the coexistence example? Or are you using a modified version of the coexistence example? Are you using a DK?

[leejh]

Sorry for the late reply.

It has been solved, and I think the problem is the config value.

(Before that, I modified it to iPhone12, not iPhone13)

[in app_config.h]

NRF_SDH_BLE_GATT_MAX_MTU_SIZE 69 --> 247

NRF_SDH_BLE_GAP_DATA_LENGTH 251 -->  251

If the MAX_MTU_SIZE and DATA_LENGTH do not differ by 4, an error occurs.

The above values do not cause an error. 

Can you explain to me this situation?

(In addition, Android phones and iPhone 8 under never occur errors. This error occurs only on iPhone8 or later)

[Mttrinh]

Hi,

leejh said:

If the MAX_MTU_SIZE and DATA_LENGTH do not differ by 4, an error occurs.

This seems strange. I don't really have an explanation as to why this is happening. Do you get the same errors when not using those values? Have you tried with other iPhones that are newer than 8(other than the ones you already tried with)? Have you tried with different iOS versions?