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Old 9th November 2012, 01:06 PM   #11
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LPC3130 can boot off from USB, don't know about the LPC43xx. Booting off from USB lets you download the code from the host avoiding the need for flash.
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Old 9th November 2012, 01:24 PM   #12
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The LPC43XX supports the DFU boot over USB in the same way as the LPC3130 does, using its internal boot ROM.
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Old 9th November 2012, 01:31 PM   #13
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Originally Posted by jonsmirl View Post
The other approach is to run Linux on it using the SDRAM chip. Linux already has audio class 2 and I2S support.
Interesting idea. Which distro did you have in mind? I was going to mention the 4300 boot ROM supports DFU but Abraxilito beat me to it.

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Originally Posted by mhelin View Post
I think the 4300 LQFP's ( LPC4320FBD144) aren't available yet.
Try Digikey; started stocking 'em back on the A2 stepping. Agree the odds of pin assignment conflicts are good---it's not the biggest package and most pins have half a dozen different functions---but if you can scrape together three SGPIO slices someplace then it's pretty easy to roll an I2S.

I don't know the LPC3130 off the top of my head but the LPC4300 I2S peripherals are duplex and include clock lines. So if one just needs a stereo USB <-> I2S then the I2S0 peripheral would be sufficient. I would guess that's a standard block NXP puts down and that the 3130 has it as well. But while Jon mentions he doesn't need more than two I2S I don't know which way they're going.

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Originally Posted by abraxalito View Post
Somewhat ironically the M0 isn't blessed with the very instruction (rotate with extend) that would make bit shuffling viable...
Why is a shift needed when copying 16 or 24 bit samples from USB to I2S? If one's doing DSP on them along the way then, yeah, probably ASR/ASL are needed to get Q0.whatever on [ -0.25, 0.25 ). But probably the M4 is doing the DSP.

Last edited by twest820; 9th November 2012 at 01:37 PM.
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Old 9th November 2012, 01:38 PM   #14
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Its not the copying the samples from USB to I2S that needs that instruction. jonsmirl originally was suggesting 15 parallel bit-banged streams of I2S using DMA, rearranging the bits in software first. That's what seems to me to need the extend bit but I'll be very happy if somebody explains a more efficient way to handle it
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Old 9th November 2012, 01:41 PM   #15
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Originally Posted by twest820 View Post
Interesting idea. Which distro did you have in mind? I was going to mention the 4300 boot ROM supports DFU but Abraxilito beat me to it.
I usually start with OpenWRT and then remove things. A 2MB image for doing this is not impossible. 4MB is easy and you'd get a web server too. Downloading 2MB over a 480Mb link is fast.

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Originally Posted by twest820 View Post
I don't know the LPC3130 off the top of my head but the LPC4300 I2S peripherals are duplex and include clock lines---I would guess that's the a standard block NXP puts down. So if one just needs a stereo USB <-> I2S then the I2S0 peripheral would be sufficient. Jon mentions he doesn't need more than two I2S but I don't know which way they're going.
I want two output lines for bi-amping a pair of speakers.

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Originally Posted by twest820 View Post
Why is a shift needed when copying 16 or 24 bit samples from USB to I2S? If one's doing DSP on them along the way then, yeah, probably ASR/ASL are needed to get Q0.whatever on [ -0.25, 0.25 ). But probably the M4 is doing the DSP.
The LPC3130 has a parallel SRAM interface that could be used to bitbang upto 15 I2S channels. That's where the shift discussion came from. I don't need 15 I2S, just mentioned it as a possibility.
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Old 10th November 2012, 07:04 PM   #16
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Originally Posted by abraxalito View Post
The LPC43XX supports the DFU boot over USB in the same way as the LPC3130 does, using its internal boot ROM.
Though only USB0, the errata (link:http://www.nxp.com/documents/errata_..._LPC43X0_A.pdf) says USB1 cannot be used for booting.

Last edited by mhelin; 10th November 2012 at 07:20 PM.
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Old 11th November 2012, 01:12 AM   #17
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Originally Posted by jonsmirl View Post
I usually start with OpenWRT and then remove things.
I imagine you'd want the 3130 for the MMU then. uClinux does support the 4350 but I don't think it implements USB audio (in fact, I'm not sure there is an open source asynchronous USB audio device class 2.0 implementation targeted to the Cortex---one option I've been toying with is porting audio-widget).
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