USB

Technical discussions related to any XMOS development kit or reference design. Eg XK-1A, sliceKIT, etc.
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rp181
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USB

Postby rp181 » Sun Nov 07, 2010 10:45 pm

Is the XC-1A fast enough to be a USB slave (info transfer)? Does it need a phy chip? Are there any examples? I downloaded the HID example, but have no idea what I am looking at.

If not USB, what is the best way to get data from the XC-1A to the computer quickly?
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waluigi
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Postby waluigi » Sun Nov 07, 2010 10:53 pm

What data speeds do you need? The XC-1A can use the onboard FTDI chip to communicate with the PC at around 500kbps-1mbps IIRC.
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rp181
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Postby rp181 » Sun Nov 07, 2010 11:05 pm

I am trying to stream video at 128x64 resolution.

What is the fastest that the XC-1A UART can go (baud rate)? Looking around, but can't find it.

Talked to folknology on IRC, and turns out you can only have full speed with bit-banging, so USB is out of the question for now.
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segher
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Postby segher » Mon Nov 08, 2010 3:08 am

rp181 wrote:I am trying to stream video at 128x64 resolution.
That doesn't say much; you want to tell us how much data per second that is.
We don't know the frame rate, or how much data one pixel is, or if perhaps
the data is compressed.
What is the fastest that the XC-1A UART can go (baud rate)? Looking around, but can't find it.
3Mbit/s. That's the raw data rate, only 2.4Mb/s can be useful data (there is
one start bit and one stop bit per byte sent); also, you'll have a really
hard time getting that data out of there: the UART has two 128-byte
buffers only, and USB has some big latencies.

1Mbit/s is doable on most hardware and OSes.
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lilltroll
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Postby lilltroll » Mon Nov 08, 2010 7:52 am

USB
Look at the schematic for the XDK, it has an USB port connected to a G4.
The chip comes in different packages for different clock speeds, look if you can reuse an existing clock.
Probably not the most confused programmer anymore on the XCORE forum.
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rp181
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Postby rp181 » Tue Nov 09, 2010 2:13 am

The video is purley for testing, so the framerate doesn't need to be that high. It is about 8k of data for 1 frame.

I managed to push the UART up to 1.5m baud with reasonable success rate. Thanks for the help!

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