FPGA Webserver

Goals: Use a cheap FPGA to support TCP, and then, use it to serve a blog.

Geting Started

Hardware: Colorlight 5A-75B Board

Get the tools: OSS CAD Suite

• yosys
• nextpnr-ecp5
• openFPGALoader & openocd

Preparing the board

Synthesize, route and flash to board:

make top && make route && make flash

For basic ARP not much additional work is needed. Run the following command:

# Test ARP (uses arping)
make arp

To test TCP, first, add route to hardcoded FPGA IP address. E.g. on Linux:

sudo ip route add 105.105.105.105 dev enp61s0 

The TCP echo server test will require re-compiling with the DEF_TCP_ECHO_EN parameter set.

DEF_TCP_ECHO_EN=1 make top && make route && make flash
# uses netcat
make tcp

Testing HTTP is a little more involved.

A set of tools live in tools/ which convert html pages inside the directory into the memory init files required.

# inside 'tools/'
python3 content_gen.py

Write the HTTP pages into flash memory. Here we write it starting from 0x40000. If you change this, do update the corresponding parameter in top.sv.

openFPGALoader -c digilent_hs2 -f -o 0x40000 --verbose-level 2 --unprotect-flash tools/content.mem
# uses curl
make http

Testing

cocotb test framework is used to automate tests found in tb/.

Install dependencies: pip install -r requirements.txt

Run tests within each directory e.g.: python3 -m pytest test_tcp_integration.py

Design

Assumptions

A set of simplifying assumptions to scope out the project.

HTTP

• HTTP1/2 protocol only.
• No TLS which means no HTTPS. This needs to be offered by a proxy.
• Headers entirely ignored.
• Only GET will be supported.

IP

• IPv4 only.
• Fragmentation unsupported.
• TCP only protocol support.

Resources

• Board reverse engineering: https://github.com/q3k/chubby75