Re: [libusb] Issues with low CDC_ACM throughput on STM32 USB-FS (sync/async)

[Xiaofan C. <xia...@gm...>]

On Sat, Apr 27, 2024 at 1:23 PM Jerri Lipp <Jer...@pr...> wrote:
>
> > On Friday, April 26th, 2024 at 4:59 PM, Xiaofan Chen <xia...@gm...> wrote:

> > You may want to use serial API
> > to try to see what is the throughput achieved first.
>
> What exactly do you mean by "Serial API"? can you be more specific? If you mean
>  talking to the tty from c using whatever posix interface, I find that much less pleasant.

Windows standard Serial API or Posix serial API.

You can even try a cross-platform library like libserialport.
https://sigrok.org/wiki/Libserialport

> As I mentioned in the original post and my previous one, I *did* use
> dd, to measure throughput directly to the tty device. Performance
> was good on one (very old) computer and bad on another (much newer).

Sorry but no idea why dd is relevant here. That is probably only relevant if
you use a USB mass storage device.

For a CDC-ACM device, the OS will assign the USB serial driver to the device.
You can not even use libusb on macOS with your USB CDC-ACM device since
there is no easy way to detach the kernel built-in driver.

If you want to use libusb, then do not use CDC-ACM at all, just program your
device as a generic USB device.

-- 
Xiaofan