Re:Low-Power $5 FPGA Module
by raverbashing on Friday July 10, 2015 @09:28AM
(#9863791)
I think you would be surprised to know a lot of the bigger FPGAs work exactly like that
You usually need a serial flash with the data, or load it on device boot (no persistent memory)
I think almost every FPGA is like that -- I think ones that have internal flash (like the Spartan-3AN) are still SRAM based and just have a flash chip in the package as well.
The only flash based programmable logic from Xilinx/Altera are CPLDs as far as I remember.
External SPI flash is pretty cheap even at low quantity (~$0.50 at qty 1 for 2Mbit, going down to the $0.30 range for low thousands)
Yeah, but FPGA dev boards usually have the required Flash chip integrated on the board rather than requiring you to supply your own.
Re:Low-Power $5 FPGA Module
by raverbashing on Friday July 10, 2015 @12:20PM
(#9864861)
Of course. Because it's a dev board
True flash FPGAs do exist -- they're used when startup time is important. Microsemi has quite a few.
Re:Low-Power $5 FPGA Module
by david-given on Friday July 10, 2015 @01:15PM
(#9865294)
How big is the bitstream for a device like this?
> The only gotcha is that the FPGA onchip memory is OTP, so it should either be loaded by external CPU over SPI, or from external SPI Flash, in both cases the SPI pins are user defined IO after bootstrap. Or then fixed configuration is burned into OTP.
Basically, while it -may- retail for $5 you will need an external CPU or flash for it to work. This sounds like a heavily restrictive limitation. I'd rather pay for a $8 FPGA module with actual persistent memory.
[2] https://hackaday.io/project/6592-dipsy