Another USB question
Posted: Fri Apr 13, 2012 5:10 pm
Dear Forum,
actually, two questions:
1: using the non-interrupt usb lib, can I probe a xud_ep if new data is available before calling XUS_Get_Buffer?
- Im guessing not... thats why there is the interrupt based lib.
2. I wrote this small echo thread:
Using libusb:
- I open the device, set the configuration, claim the interface
for x times:
- I write 32 byte
- I read 32 byte
finally I release the interface and close the device.
If x is even I can do this repeatedly.
If x is odd the first write fails (timeout) every second time I run the program.
I don't quite understand why this is. I f I just sink data without echo on the xmos, the number of transfers can be even or odd.
I know that this could have nothing to do this the xmos usb lib and just be me failing to understand a subtlety of usb in general...
help is greatly appreciated!
best,
moritz
actually, two questions:
1: using the non-interrupt usb lib, can I probe a xud_ep if new data is available before calling XUS_Get_Buffer?
- Im guessing not... thats why there is the interrupt based lib.
2. I wrote this small echo thread:
Code: Select all
void usb_echo(chanend chan_ep1_out,chanend chan_ep1_in){
XUD_ep c_ep_out = XUD_Init_Ep(chan_ep1_out);
XUD_ep c_ep_in = XUD_Init_Ep(chan_ep1_in);
char mybuffer[518];
int len;
while(1) {
len = XUD_GetBuffer(c_ep_out, mybuffer);
if (len < 0) {
XUD_ResetEndpoint(c_ep_out, null);
}
len = XUD_SetBuffer(c_ep_in, mybuffer,32);
if (len < 0) {
XUD_ResetEndpoint(c_ep_in, null);
}
}
return;
}- I open the device, set the configuration, claim the interface
for x times:
- I write 32 byte
- I read 32 byte
finally I release the interface and close the device.
If x is even I can do this repeatedly.
If x is odd the first write fails (timeout) every second time I run the program.
I don't quite understand why this is. I f I just sink data without echo on the xmos, the number of transfers can be even or odd.
I know that this could have nothing to do this the xmos usb lib and just be me failing to understand a subtlety of usb in general...
help is greatly appreciated!
best,
moritz