Transfer binary data over BLE

[3amon]

Hello all,

I am trying to write a program that that updates the firmware on an external chip from a smartphone over BLE. Currently my approach is working but quite slow and I’m wondering if there is a better approach.

Essentially, I’ve created a multi-byte writeable tag and simply doing basic write to that element. I have a temporary buffer to hold incoming data as it is being flashed and my phone/computer “updater” monitors the state of the buffer for flow control (sending more as the data is transferred to the chip being updated). Essentially a FIFO scheme. This seems to take well over a minute to send ~10k which seems extremely slow. Is that normal? Is there a better, well-known way of solving this problem? Essentially I just need to stream binary data over BLE as quickly as possible...

I looked into the OTS example but TBH I’m not confident I could create the “sender” side of that protocol. I would much prefer to stay at the upper layers of the BLE stack. Is there a better example to look at?

I’ve tried to do some searching around this forum and found people talking about the UART example but that feels like it would be even slower since it is only sending one byte at a time.

Sorry if this has been discussed elsewhere :)

Thanks,

Eamon

[MartinBL]

Hi,

Have you made sure to optimize your connection parameters and bandwidth settings? This is an informative blog that goes through the various aspects of tweaking the bandwidth: Bluetooth 5 speed: How to achieve maximum throughput for your BLE application.

Here are a few tables showing what bandwidths you can expect: Bluetooth low energy data throughput. Note though, that the values in the tables are measured between two nRF52840's. Your phone, tablet, computer, etc. do not necessarily support the same bandwidths and you can never expect to get the same throughput between all devices. 

It is not necessarily true that the UART example only sends one byte at a time. You can tweak all the bandwidth parameters on that example as with any other, and it can be a good place to start if you want to transmit a lot of custom data. You might also be interested in the Experimental: ATT_MTU Throughput Example.