For quite a while I wouldn’t have said, it’s impossible, but wouldn’t put much effort in it either. Why, if you have a spare $1 microprocessor that can run a simple communication stack like netpp.
Well, sometimes it’s the time to try something else: Running a soft core CPU (ZPU) on small FPGAs has found some interest, due to the limited resource consumption. The ZPU will even fit on a $5 FPGA and still leave some space for specific interfaces like motor control. It is a slow stack machine, even the fastest pipelined implementations don’t really beat the MIPS alike architectures, however this doesn’t bother us when we just have to configure a set of registers, moreover, the ZPU architecture compensates with quite some code density.
To keep a long sermon short: A full netpp stack running over a UART interface fits in less than 15kB of memory. And runs on a MachXO2-7000 from Lattice, for example, with less than 50% logic usage.
Who’s still saying that an FPGA is too dumb for the internet?
Ok, there’s one little missing piece: The TCP/IP stack and the ethernet MAC. For this purpose, I’m using a esp8266 module. You’re right, we don’t want to do the full networking on the FPGA – yet.
The solution was presented on the Embedded World Conference 2016. The paper is available for download below.