Kevyn-Alexandre Paré wrote:
> Here's the code and output of my test. I'm trying to understand what's going
> wrong! I mean that I'm expecting the callback function "cb_xfr" from my bulk
> transfer to be called after libusb_submit_transfer is called. I'm
> communicating to a FPGA through a Cypress USB (FX2) and It's working with the
> synchronous API but not yet with the Asynchronous one??? I have put the
> usbmon output that I'm still reading and learning about it. If you see
> something let me know!
> ...
> static int benchmark_in(uint8_t ep)
> {
> static uint8_t buf[6] = {0x2,0xa0,0x3c,0x23,0x3,0x0};
> static struct libusb_transfer *xfr;
> int num_iso_pack = 0;
>
> xfr = libusb_alloc_transfer(num_iso_pack);
> if (!xfr)
> return -ENOMEM;
>
> libusb_fill_bulk_transfer(xfr, devh, ep, buf,
> sizeof(buf), cb_xfr, NULL, 0);
>
> gettimeofday(&tv_start, NULL);
> printf("-->SUBMIT length:%d\n", sizeof(buf));
> return libusb_submit_transfer(xfr);
> }
When you are doing a bulk IN transfer, you always need to specify a
buffer that is as large as your endpoint size. Remember that a USB
device is never told how much data to send. It is merely given a signal
that says "GO!". At that point, the device has the perfect right to
send 512 bytes. However, the host controller will only have allocated
enough bus time for 6 bytes. Your device steps on the next device's
slot. That's a protocol violation called "babble".
> int main(int argc, char **argv)
> {
> ...
> rc = libusb_set_interface_alt_setting(devh, 1, 0);
It is not useful to select an alternate setting unless you have more
than one. If you only have bulk pipes, then you have no need for
alternate settings.
> libusb_clear_halt(devh, 0x06);
> libusb_clear_halt(devh, 0x88);
Why do you call clear_halt here? In virtually every case, that's
unnecessary superstition.
Are you sure your device has queued up data to send? What is it that
tells your device to put data in the FX2 FIFO?
--
Tim Roberts, t...@probo.com
Providenza & Boekelheide, Inc.
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