Re: seek for help on Libusb & STM32

Best regards,
Pradeepa Senanayake.
On Mar 10, 2014 10:08 PM, "Pradeepa Senanayake" <[email protected]>
wrote:

> Hello Xiudong,
>
> There is nothing wrong in your english. Your requirement is crystal clear.
> Using VCP it is hard to achieve that speed. So the best way you can tackle
> the issue would be to implement a custom class. This can be done easyly by
> changing the descriptors in your CDC example too.
>
> The easiest way is to have one interface. Within that interface have one
> bulk in and one bulk out endpoints. If you need you can have another bulk
> out endpoint to send any commands. That you should decide.
>
> In the CDC example by ST there are plenty of class specific coding. You
> will have to carefully remove them. There will be a few functional
> descriptors too that you will have to remove. ( I assume that you know USB
> basics. If  not please refer to websites like 'usb in a nutshell' or 'usb
> made simple' )
>
> Obviously bulk.c will not work with your current USB configurations.
> Because it is expecting a bulk in and out endpoints in your interface 0.
> But your interface 0 only contains one interrupt endpoint. That should be
> the reason why it is failing.
> Start by changing the firmware in the discovery board. Implement a vendor
> specific class.
>
> I m just giving you a overall view of the matter. Attempt the changes and
> if you come across any issue please don't hesitate to send a mail.
>
> Thank you,
> 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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