Re: [LAU] zedboard fpga dev board and linux audio

On 01/02/13 06:22, Len Ovens wrote: 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