File transfer speed from iOS (iPhone X) to NRF52840

[lbe]

Hello everyone,

In the past few days I have been struggling with the following issue: I have a file on my iPhone, I want to send it to the NRF52840 using BLE (the softdevice).

I had a look at the Image Transfer demo app, which although not working properly on the iPhone X (the progress bar stops before the end, it was an already reported

bug), gave me good pointers on how to configure my application. So, I was able to use the maximum MTU (185), the minimum connection interval allowed by Apple (15ms, as I

don't have HID) and the DLE feature. The correct setting of these parameters is confirmed by a WireShark sniffing using another NRF52DK as sniffer.....

But.....but when I do the file transfer, I am never able to obtain a result better than 50kbps. So, a file of about 2MB takes about 6 minutes to transfer.....

Do you have any suggestion on what else I should investigate to have a better speed?

[ovrebekk]

Hi

A couple of follow up questions:

1) Have you checked the length of the packets received on the nRF52 side to verify that the 185 byte MTU size is actually used?

2) Have you checked how often packets are sent to see if you are able to send more than one packet pr connection interval?

3) Have you made sure to use write commands (write without response) rather than write requests to ensure that you don't get slowed down by having to wait for the write responses from the nRF52?

Best regards
Torbjørn