The standard STM32F407 USB audio driver only supports 48k, is there any info available to up it to higher speed?

[Robmar]

The standard STM32F407 USB audio driver only supports 48k, is there any info available to up it to higher speed?

[mohamed.ayed]

Hi @Robmar​ 

Our legacy ST-USB lib support only audio 1.0 it support only FS speed but for HS you need to switch to USB Audio 2.0 you can use AzureRTOS middleware stack it support both Audio1.0 and Audio 2.0.

[Robmar]

Not sure the rtos overhead or memory requirements would fit unfortunately ​

[Robmar]

Thank you Mohamed, appreciated. Do you know if I can use the middleware stack without having to use the RTOS itself, it's a little short on memory as it is. It doesn't look like it's going to fit:

This I guess:- "Azure RTOS USBX is a high-performance USB host, device, and on-the-go (OTG) embedded stack. Azure RTOS USBX is fully integrated with Azure RTOS ThreadX and available for all Azure RTOS ThreadX–supported processors."

[mohamed.ayed]

@Robmar​  AzureRTOS stack support both RTOS (with threadx) & Standalone mode you need juste to update you middleware 6.2.0 and then define UX_STANDALONE in ux_user.h

you can see HID Stanndalone application:

https://github.com/STMicroelectronics/x-cube-azrtos-h7/tree/main/Projects/NUCLEO-H723ZG/Applications/USBX/Ux_Device_HID_Standalone

we have a draft ux_device_audio application here :

https://github.com/STMicroelectronics/x-cube-azrtos-h7/tree/dev/usbx/Projects/STM32H743I-EVAL/Applications/USBX/Ux_Device_Audio

[Robmar]

Do you think I could set higher board rates in usbd_conf.h ?

#define USBD_AUDIO_FREQ   48000

[Robmar]

Thanks, very useful. The draft example you reference is for the H7, is there any way to change that easily to F407? Came across this before, a sample for an F411, IDE refuses to change the MCU type, so I had to hack the .cd and other files replaces all the MCU references, took me nearly an hour, but quicker than recreating the project.

[Piranha]

https://github.com/hathach/tinyusb/tree/master/examples/device/audio_test_multi_rate

[Robmar]

Not much of a description on that site, any idea what it does?

[AScha.3]

see in main.c :

[Robmar]

I've been told that the standard USB audio driver on the STM32F407 can handle higher rates just by changing the descriptor. Anyone any idea on that?

[LCE]

In case you have a dev board: try it! Worst case you get some blue screens... :D

If you don't have a dev board, get one.

If I'm in doubt about an STM32's capabilities, I definitely try to make it work on a Nucleo board or so before putting it on a custom PCB.

[Robmar]

haha sure, but I could not see in the descriptors where the baud rate is defined, there was no obvious define for 48000...!

It's just a long list of stuff with not much commenting!

[Piranha]

> Not much of a description on that site

https://docs.tinyusb.org/en/latest/reference/getting_started.html

Together with the examples... enough for me.

> any idea what it does?

Isn't it obvious even by the folder name?

> Could it be as easy as just changing that to 96000, or 192000?

https://github.com/STMicroelectronics/STM32CubeF4/blob/e92669fc501fb8b7512fd6890a6eb379b6ae90c5/Middlewares/ST/STM32_USB_Device_Library/Class/AUDIO/Src/usbd_audio.c#L38

> Could it be made selectable at boot time by replacing with a variable?

Other people have already implemented that and more necessary features. That's why, instead of messing with a broken bloatware, they developed an actually usable USB stack, like TinyUSB.

> Worst case you get some blue screens

An externally connectable device cannot make BSOD. If it can, that's a bug in the host OS or drivers.

[LCE]

>> Worst case you get some blue screens

> An externally connectable device cannot make BSOD. If it can, that's a bug in the host OS or drivers.

Well, that's my USB experience from about 15 years ago when working with Cypress FX2 and the Cypress driver and Windows x (was that still XP?).

At that time, one error in the descriptors and Windows was very blue...

[Piranha]

It's definitely a bug in some component. Most likely in the Cypress driver, less likely in a Windows integrated drivers or USB stack.