https://devzone.nordicsemi.com/f/nordic-q-a/85240/how-to-set-ble-tx-data-lengthsoftware version :nrf connect SDK 1.6.1 hardware:nrf5340 ble stack:ble 5.0 ble central: iphone x app ble client:nrf5340 kit question:I was failure to set Tx len 251 bytes,this makes the Bluetooth communication rate extremely low. Accordingen-USTelligent Community 13Tue, 01 Mar 2022 08:38:15 GMThttps://devzone.nordicsemi.com/thread/355448?ContentTypeID=1Tue, 01 Mar 2022 08:38:15 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3f7cb4a5-1c4d-4335-8d77-d59cad774b87Simonr<p>Hi</p> <p>iOS devices are known to not play well with the maximum MTU sizes of 247 bytes I&#39;m afraid. The highest allowed MTU by iOS devices is 184 bytes, so try setting the max to that, and data length to 187 bytes. Is your application based on the throughput sample, or is this a custom project?</p> <p>Did you see the note for nRF5340 devices in the Throughput sample? If you&nbsp;<span>use nRF5340 DK, the additional configuration of the network core will be taken from the&nbsp;</span><code><span>child_image</span></code><span>&nbsp;directory. For more details see:&nbsp;</span><a href="https://developer.nordicsemi.com/nRF_Connect_SDK/doc/latest/nrf/ug_multi_image.html#ug-multi-image-variables"><span>Image-specific variables</span></a><span>.</span></p> <p>Best regards,</p> <p>Simon</p><div style="clear:both;"></div>