lib_usb usb.urb_status = -71

[Endre]

Hello,

I'd like to get some hint for USB debugging.

I made an USB app based on the lib_usb doc and xud_cdc.xc.
It's a vendor specific device and has 1 bulk out and 2 bulk in endpoints.
I have tried to send and receive packets with pyusb and libusb (Linux).

Sending packets to the out endpoint works, but receiving one from the input endpoint fails immediately with I/O error.

In xC side the "result = XUD_SetReady_In(inEp, curTxPacket->data, curTxPacket->len);" call returns with 0, but "case XUD_SetData_Select(inCh, inEp, result)" is never unblocked.

In wireshark I see that for the "host->XMOS URB_BULK in" request there is a "XMOS->host URB_BULK in" response with "usb.urb_status = (-EPROTO) (-71)".
I'd like to figure out why XMOS replies with -71.
I made text searches on lib_usb for 71 in various forms (decimal, hexadecimal, 2's complement), but I found nothing except for a comment in a jump table.
I have also taken a look into the xud main loop, but I couldn't figure out it yet.

Has anyone some idea why the xud code could respond with -71 for "bulk in" request?

Thanks for any help!

[Endre]

I have recently found AN00136 (USB Vendor Specific Device). That could help.

[Endre]

I didn't go far with the tutorial yet. That uses the sync API while I try to use the async.

Meanwhile I have uploaded my source to here.

I have over-complicated it a little bit by adding XUD_STATUS_ENABLE to the endpoints and trying to hanlde XUD_RES_RST (it solved nothing).

[Endre]

This simple task works, but works only when there is no debug_printf() in the loop:

Code: Select all

void echoHandler(chanend outCh, chanend inCh) {
    XUD_Result_t result;
    uint8 buf[512];
    unsigned len;
    XUD_ep outEp = XUD_InitEp(outCh, XUD_EPTYPE_BUL);
    XUD_ep inEp = XUD_InitEp(inCh, XUD_EPTYPE_BUL);
    XUD_SetReady_Out(outEp, buf);
    while (1) {
        select {
            case XUD_GetData_Select(outCh, outEp, len, result):
                if (result == XUD_RES_OKAY) {
                    // debug_printf("%d bytes received.\n", len);
                    // send data back
                    XUD_SetReady_In(inEp,buf, len);
                }
                break;
            case XUD_SetData_Select(inCh, inEp, result):
                // debug_printf("packet sent.\n");
                XUD_SetReady_Out(outEp, buf);
                break;
        }
    }
}

So the debug_printf() could cause some USB timing issue. But removing debug_printf() from rxHandler() and txHandler() didn't help.

[Endre]

Ahhhhh....

For make it working I had to remove debug_printf() from rxHandler() and txHandler() and also from echoTask() (please don't mix up echoTask() with echoHandler(), echoHandler() only presents in an other variant of the project).

I don't understand why debug_printf() in echoTask() caused problems. echoTask() runs on a different tile (not on the USB tile) and debug_printf() uses XTAG as an output device. So I don't understand how can it cause interference with the USB tasks and endpoints which are running on the USB tile.

My host side test app is even a simple one. It sends a packet than receives a response via a simple blocking API:

Code: Select all

import os
import usb.core

devs = usb.core.find(find_all=True, idVendor=0x20b1, idProduct=0x500)
deva = []
for dev in devs:
    deva.append(dev)
    print str(dev)

assert len(deva)
dev = deva[0]
dev.set_configuration()
for i in range(32):
    text = "Hello XMOS! cnt:{}".format(i)
    print "Sending: {}".format(text)
    dev.write(1, text)
    ret = dev.read(0x81, 256, 1000)
    sret = ''.join([chr(x) for x in ret])
    print "Received: {}".format(sret)

Can someone please give an explanation for this anomaly?