Problem with usb_control_msg

[Jonatan]

Hi

I'm trying to use V-Usb to control a display, among other things. To send text to the display I thought I would use control messages, using usbFunctionWrite() to get the string data.

I've got the communication up and running: there are valid calls to usbFunctionSetup(), but usbFunctionWrite() is never called. Thus I never get any data.

I've created a very basic program based on libusb running on Ubuntu. When I call usb_control_msg() to send the string data i get error -75 returned ("Value too large for defined data type"). I need some help to decode that!

My call to usb_control_msg() looks like this:

Code: Select all

char *buf = "Hello World";
usb_control_msg (handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_OUT, 123, 0, 0, buf, strlen (buf), 5000);

[Saimon]

You post:
"My call to usb_control_msg() looks like this:

Code: Select all
char *buf = "Hello World";
usb_control_msg (handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_OUT, 123, 0, 0, buf, strlen (buf), 5000);"


You try to send data to default endpoint 0, thus try to use "USB_ENDPOINT_IN" flag
Ma be i'm wrong? but try to use this:
"
char *buf = "Hello World";
usb_control_msg (handle, USB_TYPE_VENDOR | USB_RECIP_DEVICE | USB_ENDPOINT_IN, 123, 0, 0, buf, strlen (buf), 5000);"

I hope it help to you!

[Guest]

You were absolutely right! Using USB_ENDPOINT_IN I get no error message.

However, there is one more problem: usbFunctionWrite() is still never called.

I have USB_CFG_IMPLEMENT_FN_WRITE enabled in usbconfig.h

This is my usbFunctionSetup:

Code: Select all

static uint8_t usb_buffer [256];
static uint8_t usb_pos, usb_func, usb_remaining;

usbMsgLen_t usbFunctionSetup (uchar data[8])
{
    usbRequest_t*   rq = (void*) data;

    usb_func = rq->bRequest;

    switch (usb_func) {
    case LUXREQ_DISPLAY_STRING:
        usb_remaining = rq->wLength.word;
        usb_pos = 0;

        return USB_NO_MSG;

    default:
        return USB_NO_MSG;
    }
}

I've used a display to make sure that the first switch-case (LUXREQ_DISPLAY_STRING) is reached, and rq->wLength holds the correct length (the length of data sent by usb_control_msg() from the PC).

Any ideas?

[ionte]

The message above was sent by me. Forgot to login.

[Saimon]

If you need to call usbFunctionWrite? you must return 0xFF in usbFunctionSetup!
This is necessary for V-USB lib driver! my email: lleeloo@mail.ru
Sorry for my English!

[ionte]

Hi,

I do return USB_NO_MSG which is defined as 255 in usbdrv.h:

Code: Select all

#define USB_NO_MSG  ((usbMsgLen_t)-1)   /* constant meaning "no message" */

I tried with the value 255, to avoid the macro, but same result.

Any other ideas?

[christian]

And did you configure V-USB with USB_CFG_IMPLEMENT_FN_WRITE defined to 1 in usbconfig.h?

[lll7]

I've got the same problem usbFunctionWrite() is never called. I've made all those steps with configuring usbconfig.h also my program returns USB_NO_MSG in usbFunctionSetup(), i've check it by using blinking diode. In usbFunctionWrite() i just want to flash a diode but it dosen't work. Have anyone have some ideas, can it be becouse of the HID device type(Mouse) witch i'm using?

[Saimon]

Hi! Try to write new clear project and call usbFunctionWrite. Make shure that cstack and heap are correct. And if you try to call usbFunctionWrite in HID example, i'm not shure that usbFunctionWrite is called by V-USB driver at all.

[lll7]

Problem solved it was because of HID type of my device i've changed it and all works fine.

[tommyjunge]

Hi,

Problem solved it was because of HID type of my device i've changed it and all works fine.

is it not possible to send usbFunctionWrite to an HID device?

Do I need to use LibUSB in this case or can I do the same thing with HID?

Thanks, Tom

[christian]

If you want to send arbitrary control messages, you need libusb. Otherwise you can only send those controls defined in the USB HID paper.

[tommyjunge]

Where can I find the HID USB paper?

[christian]

See http://www.usb.org/developers/hidpage/