Dongles for STM32MP157F

[OBaselga]

Hi everyone,

I'm not sure if the following questions depends on OpenSTLinux - drivers for example - or STM32MP1 hardware.

I have the STM32MP157F MPU and I would like to integrate Bluetooth 5.0 . My main idea was to connect a Bluetooth 5.0 dongle into my MPU, but a question crossed my mind: Does any dongle work for STM32MP157F or should it have any specific feature? Until now, I had found this kind of dongles <link>, will it work?

Besides, I would like to integrate another dongle, in this case a SD card dongle - as I would like to have the main SD mounted with OpenSTLinux, which occupies the SDMMC port, and a secondary SD card exclusively dedicated to storage. I have the same question, does any dongle work? This time, I had found this one <link>.

I don't know if incorporating dongles is the best option to solve my problem, anyway I am open-minded to new ideas 😉

Thank you,

Oscar

[PatrickF · Accepted solution]

Hi,

Are you using an ST board such as STM32MP157F-DK2 ?

Is the embedded Bluetooth BLE 4.1 on this board not enough for your usage ?

You could probably add an USB dongle, but we have no list of such devices. I think using one with available Linux driver should be ok. You may need to adapt DT (e.g. disable embedded BT) or install some patch or driver.

See an example for WLAN dongle : How to use Edimax EW-7811un-V2 WiFi dongle on STM32MP157A-DK1 Discovery Board ?

For external storage, using an USB storage dongle is maybe more straightforward than SD-card with an USB adapter. USB mass storage should work out of the box.

Please note that for STM32MP15x-DKx and STM32MP15x-EV1 board, the 4 x USB Type-A connectors are limited to 500mA each and using 4 x 500mA might not be supported by the 5V 3A supply if there is strong processor and board peripherals activity.

Regards.

[OBaselga]

Hi Patrick,

Thank you for your answer.

Yes, I'm using STM32MP157F-DK2. I got strictly ordered to use BLE 5.0, so 4.1 isn't enough this time. Well! I'm going to purchase a dongle supported by Linux and try to make it works.

About external storage, the main idea was to use an SD-card, but perhaps a USB is better, as you said. I want a minimum data rate of 1.5 MByte/s while the mission of the CA7 is just to write to external storage and send some data through BLE, so at first glance I would say that there will be no problem.

Regards,

Oscar

[OBaselga]

Hi @PatrickF​ ,

I have finally bought this Bluetooth 5.0 dongle: https://www.pccomponentes.com/asus-usb-bt500-adaptador-usb-bluetooth-50 and it seems that is working fine. Testing how it is managed, I have achieved to scan devices and establish a connection, but there is a problem: when a connection is just established, it finishes almost at the same time. Browsing in the Internet, community said that a bug is present provoking the "btusb autosuspend" happens. This means that dongle is continuosly restarting an thus removing all connections. Here is the clearest solution I have found: https://bbs.archlinux.org/viewtopic.php?id=236479 and https://ljn917.wordpress.com/2018/03/01/disable-bluetooth-autosuspend/ . My problem is that I don't know where to set up the variable "btusb.enable_autosuspend=n", as "/etc/modprobe.d/" directory is empty and I don't know how to set boot kernel parameters. Can you think of something?

Regards,

Oscar