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L2CAP with BLE and STM32

yosoufe — Tue, 05 Jan 2021 19:01:01 GMT

It has been few weeks that I am trying to learn about Bluetooth low energy (BLE). This is the first time I code for bluetooth and I spent a lot on learning the basics. I managed to get my python script to communicate with the Nucleo board via the BLE expansion board. It seems the BLE is not designed for relatively large data. Every packet is like around 20 bytes of data. I read about L2CAP which seems it can increase the throughput. But I do not find an example or any code to use the BLE and L2CAP. L2CAP is marked as supported in the BLE exansion board but I do not know how to activate it and how it works.

My purpose is to be able to send the ADC measurements over BLE to the PC and do the rest of calculation on PC. It has been impossible to have a good speed of data transfer for this purpose. For example when I send 250 bytes from nucleo board to PC without L2CAP, it takes more than 1 seconds. The alternative is to do calculations on the nucleo board and use the BLE just as a notification.

If you know about the L2CAP and BLE please help me. I do not find anyway to send data using L2CAP with the bluenrg library as a server. bluenrg library has few functions to receive L2CAP stuff or sending as a client, but I could not find anything to initiate the communication over the L2CAP as server.

Thanks

Yousof

Anyway to un-publish the blog?

yosoufe — Fri, 25 Dec 2020 20:58:18 GMT

Hi,

Is there any way to un-publish a blog? I am writing a blog and save it as a draft. And sometimes I click on "publish" instead of "save as draft" by mistake. Is there anyway to undo it?

It is not possible to easily delete the blog and recreate it, because I need to upload the images and videos again. Otherwise clicking on the copied image, results in "image not found" error message.

Even a pop question, asking for confirmation like "You are going to publish the blog. Are you sure? Continue?" or something like that would be useful to avoid publishing by mistake.

Thanks

How are you going to connect the sensor?

neuromodulator — Thu, 26 Nov 2020 22:53:35 GMT

The only requirement for the "experimental design challenge" is to use the vibration sensor. How are you going to use it? I suppose most (if not everyone) will sample the analog signal, but what are you going to use to sample it? Are you going to use the provided STM32 MCU, a different MCU. a DAQ, or something else?

As of me I still haven't decided yet. I got a NI DAQ, a DMM with sampling capabilities and of course a bunch of MCUs and FPGAs. the NI DAQ is probably the easiest to use, its 200 ksps @ 16 bits. Then my DMM could sample up to 1msps @ 16 bits, but not continuously, or at much higher resolution but also a much slower speed. Then the provided STM32 can sample at up to 3.6 Msps @ 16 bits, (and eventually at higher speed through interleaving) but requires much more effort as it needs to be programmed.

How does the sensor communicate?

parasquid — Tue, 06 Oct 2020 20:16:10 GMT

Is it through voltage fluctuations?

I can see that there is only one wire as the signal. Is it modulated somehow, or is there a carrier wave?

I wasn't able to find the information in the datasheet linked to the article, but maybe someone can point me in the right direction?