Re: seek for help on Libusb & STM32

Best regards,
Pradeepa Senanayake.
On Mar 10, 2014 12:18 PM, "Duan Xiudong" <[email protected]> wrote:

> Hello   Pradeepa,
>
> I'm glad you can reply. Thank you very much for your instruction.
>
> Maybe I didn't made it clear. My application do something like data
> sampling and acquiring. These data should be sent to PC with a speed of
> 500KByte/s or even higher. As you know, it is difficult for  VCP to reach
> such a high speed. I guess it might be possible using USB bulk transport directly
> instead of VCP. And that is why I want to apply LibUSB in my application.
>
> I got another link of discussion between you and another guy
>
> http://libusb.6.n5.nabble.com/LibUSB-and-the-STM32F4-Discovery-td5712505.html#a5712516
>
> After reading this, I think my problem might be inside the device
> firmware. I changed it from ST official VCP demo project.(I change only a
> little, just delete those don't match STM32F4 Discovery board.) Though it
> can work as a COM port, it might not fit with the Libusb example code(
> bulk.c in libusb-win32-1.2.6 zip file from official website).
>
> As I had learned, there're 2 interfaces in CDC class. One has a interrupt
> EP for CMD, the other has 2 bulk EPs for Data. If I want to use the libusb
> bulk read function to get data, what change should I make to the firmware?
> Should I delete the former interface? I'm totally new to USB and CDC. I
> hope you can give further advises.
>
> As you might figure out, my English is not very good. And there is few
> information about Libusb in Chinese. So it is a little hard for me to get
> help around. If you can give me some detail advises or send me some
> example codes (if possible), I will appreciate it very much.
>
> Thank you once more.
>
> Best wishes,
> Daniel Duan.
>
> PS:I just find I set my name wrong. In fact,Duan is my family name, which
> comes first in our Chinese tradition.
>
>
>
>
> 2014-03-10 11:30 GMT+08:00 Pradeepa Senanayake <[email protected]>:
>
>> Hello Duan,
>>
>> Since the firmware you use is for a VCP it will be enumerated within the
>> PC side as a COM port. In that case you can directly use serial writing
>> methods to access the device. I don't think that you need libusb in that
>> case. But if you wan't to have lets say a Vendor Specific class with your
>> own descriptors (ie. Endpoint types, etc. ) then LibUSB will come in handy.
>>
>> For your application, if COM port is enough, I would recommend using
>> methods to access COM port rather than using LibUSB. Do a google search
>> with keywords such as " Writing to a COM port using visual studio" and you
>> will get plenty of hits.
>>
>>
>> >>   I  learned  you had done similar works from here
>> >> https://sourceforge.net/p/libusb-win32/mailman/libusb-win32-devel/thread/CA+1tQ71CeMubpzV2rBHPnWQ5Zcnihx1e>>>>
>>   [email protected]/<https://sourceforge.net/p/libusb-win32/mailman/libusb-win32-devel/thread/CA+1tQ71CeMubpzV2rBHPnWQ5Zcnihx1e24_1wqFHicofGqsi0Q@mail.gmail.com/>
>>
>> In the above link, he is not using VCP. That is why it is easier to use
>> LibUSB. I'm just a LibUSB user (not a developer) so the devs will correct
>> me if I am wrong.
>>
>> Please refer to this discussion,
>>
>>  http://sourceforge.net/p/libusb-win32/mailman/message/31338949/
>>
>> it will hopefully clear most of the doubts.
>>
>> Hope I helped.
>>
>> Thank you,
>>
>>
>>
>> Best Regards,
>> Pradeepa Senanayake.
>>
>>
>> On Sun, Mar 9, 2014 at 2:22 PM, Duan Xiudong <[email protected]>wrote:
>>
>>> Hello   Pradeepa,
>>>
>>>      I am a student form China. I'm trying to get some data  using USB
>>>  from a board based on STM32F4xx chips. Right now I'm trying it on  a
>>> STM32F4discovery  board.
>>>
>>>     On  the  device side,  I  implement a  Virtual COM Port project form
>>> ST firmware.It can work well as a COM port with PC.
>>>
>>>     And now I download  libusb-win32-1.2.6 , generate and install the
>>> drivers (INF file) as  it requires. Then I  test  it on VS  using the
>>> example code from the official  website. It seems  that PC can get the
>>> configuration information correctly,  but can not execute  any bulk_read
>>> operation. When it runs to * usb_bulk_read()* or *usb_submit_async()*
>>> function, the program ends with error.
>>>
>>>     I  don't  know where the problem is.  Is there any problem  on PC
>>> side codes?  OR something  wrong  with device firmware? It puzzled me a lot.
>>>
>>>        I  learned  you had done similar works from here
>>>
>>> https://sourceforge.net/p/libusb-win32/mailman/libusb-win32-devel/thread/CA+1tQ71CeMubpzV2rBHPnWQ5Zcnihx1e24_1wqFHicofGqsi0Q@mail.gmail.com/
>>>
>>>       I hope you can give me some instructions. If you're kindly  to
>>> offer some help, I will give more details.
>>>       Thank you very much!  Hope  for  your  reply.
>>>
>>> --
>>> Daniel
>>>
>>
>>
>

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