On 02/01/13 16:41, Simon Wise wrote: > On 01/02/13 06:22, Len Ovens wrote: >> >> On Thu, January 31, 2013 9:42 am, Kelly Hirai wrote: >>> im wondering if anyone has played with these and what kind of >>> performance they might expect. >>> >>> http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,1028&Prod=ZEDBOARD&CFID=412288&CFTOKEN=58875851 >>> >>> >>> assuming nothing breaks this year, it might be in the budget >> >> Looks interesting. What are you going to try to do with it? Should >> make a >> nifty portable audio recorder. Should be able to be used as an ether net >> sound card. I don't know how well it would work as a guitar effects >> box or >> synth (hmm no midi in). It is meant to be a note pad. The thing you >> can't >> tell from the write up is if there is any hardware that would interfere >> with low latency audio. My netbook has that problem with the wireless >> chip. I can have low latency audio or wireless, but not both. > > It is certainly nothing like a note pad, it is an evaluation board > with a chip with programmable logic, designed for embedded systems: > > http://en.wikipedia.org/wiki/Field-programmable_gate_array > > The chip also has an ARM CPU and various other sections as well, and > it is mounted on an evaluation board that has the output pins wired up > to some RAM, an SD card, a Gbit ethernet controller and various other > useful things. The software required to program it is included (it has > linux versions). If you want to explore FPGA logic programming it > could be really interesting. For example seeing what you could do with > a 5Mhz bitstream audio output into a very simple digital amp circuit, > or for various DIY interfaces through the GPIO ports. For a few more > $$ there is a pack of 15 cards that plug into those GPIO ports, > including some ADC/DAC stuff. There seem to be some interesting high > speed connection pins also. Being able to program the logic circuits > and implement things on that level allows very different kinds of > approaches. Perhaps many channels of audio output using bitstreams and > fairly simple amplifier circuits which could then be used with the > Gbit ethernet to provide an interesting sound output device. Just > playing with ideas here. > > Their other FPGA models without the fixed CPU etc might be interesting > as well, you can program a CPU in them if you want, though it won't be > as fast as one with fixed logic it is certainly more flexible if you > don't need much in the way of a CPU. This kit is half the price of the > one above: > > http://www.xilinx.com/products/boards-and-kits/HW-SPAR3A-SK-UNI-G.htm > > There are open source hardware designs that can be put into these > FPGAs as well ... look at: > > http://opencores.org/ > > There is another hybrid approach to programmable logic plus a CPU that > may be a much more natural fit with audio DSP programming ... > > http://www.stretchinc.com/products/s7000.php > > here the idea is that the programmable logic is integrated with the > CPU via 32 128-bit registers so that the logic part can be programmed > as custom instructions which are run in the CPUs instruction pipeline. > This is quite different to the Zedboard approach which puts the > programmable logic more as peripheral devices to the CPU. The Stretch > seems reasonably mature, it is the third generation since the original > version (in 2004, with PPC CPUs instead of ARM ones). FPGAs have been > around for a very long time, but it seems only recently got more > useful or at least sellable. > > The big selling point for Stretch on their website is that their > compiler will compile functions written in C or C++ into their > programmable logic that can then be run as single (big) instructions > in the CPU. Also it seems the logic section has somewhat larger units > of logic ... in the Zedboard you have a large array of 4-bit look up > tables and sets of 4000-bit ram modules, connectible to very > configurable GPIO pins while in the Stretch they seem to have adders > and multipliers and so forth (probably much more useful in the context > of compiling code written as a function in a procedural language). No > need to learn one of the hardware logic languages, if the compiler is > good enough to do that for you. From the site it seems they have done > quite interesting things with video codecs, image recognition and such > like. The logic part can be reset in 100 microseconds, so for audio > use that is only about a 5 sample wait for a new set of CPU > instructions to be loaded. Potentially very interesting. > > Simon > _______________________________________________ > Linux-audio-user mailing list > Linux-audio-user@xxxxxxxxxxxxxxxxxxxx > http://lists.linuxaudio.org/listinfo/linux-audio-user fpga seems a natural way to express in silicon, data flow languages like pd, chuck, csound, ecasound. regarding the stretch, the idea that one could code in c or c++ might streamline refactoring code, but i'm still trying to wrap my head around designing graph topology for code that is tied to the program counter register. nor do i see the right peripherals for sound. perhaps the g.711 codec support is software implementation and could be rewritten. need stats on the 8 bnc to dvi adapter audio port. on the xlinx side, would you really have to hack it in vhdl? rewriting opcodes / function blocks in vhdl could be rewarding but still, that would be the end of my time. k. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
