Uart384

UART384 - FPGA devboard & USB-stick

This is a mini-devboard for the Lattice iCE40LP384, the BEST 🔍 FPGA ever!

Features:

• USB-stick form-factor
• USB is connected to Silabs CP2102 USB-to-UART bridge
• Tiny Lattice iCE40LP384 with connections:
  • 384 LUTs/FFs
  • UART
  • 2 LEDs
  • 1 push-button
  • 8 GPIOs on pinheader
  • 32MHz oscillator
• small flash for bitstream
• TC2050 connector (bottom side) for programming the flash

NOTE: device is not programmable via USB

Gateware

"Why?", you ask?

Mostly for fun and training; there are a few gateware options available in this repository:

Entropy generator

gateware/entropy_generator.v

High quality entropy source using metastability from ringoscillators fed into the spongent hash algorithm.

This is one of the original reasons this board was created for: I wanted a USB stick that generates cryptographically sound entropy that can be used to enhance system entropy on linux.

gateware/tools/seedrng.py can be used to receive the entropy and inject it directly into the kernel entropy pool.

SPI and GPIO over UART tunnel

gateware/relay_spi.v

This variant allows complex muxing of SPI lines from an SPI master core to all GPIO1..8 pins, as well as the internal program flash. All these pins can also be muxed as GPIO input or output and controlled/sampled. All that via a simple UART protocol.

This gives full control of inputs and outputs, as well as efficient SPI communication via SPI core, in any configuration. The SPI core is used for SPI transfer by pulling RTS down, then CS is automatically pulled down and data is seemlessly interchanged between SPI and UART.

This e.g. allows reprogramming the internal flash, or external SPI devices, including Lattice iCE40 FPGAs if GPIOs are used to trigger their CRESET. Since CDONE can also be sampled, this also allows programming any iCE40 FPGA in slave mode, fully replacing any other needed programming board to flash/program a Lattice iCE40 FPGA. Note that the FPGA is pretty much full, no further features will be added to this gateware.

See gateware/tools/spi_device.py for general SPI command abstraction, and gateware/tools/flashtool.py and gateware/tools/spi_device.py as an example client to work with the onboard (or any other) serial flash.

Ring oscillator entropy generator

gateware/ring_noise.v

Low quality entropy generator using metastability from ringoscillators fed into a linear feedback shift register.

UART pass-through

gateware/uart_passthrough.v

A simple example that only passes UART signals along to the GPIO header and shows changes on RX/TX lines on the LEDs (with some timeout).

Variable delay ring oscillator

gateware/variable_ringoscillator.v

Experiments with a ringoscillator with a reconfigurable delay-line. Delay can be changed at runtime via UART.

License

The hardware (Schematic, PCB) is licensed under CERN-OHL-W v2. See cern_ohl_w_v2.txt.

The software is licensed under LGPL v2.0, unless specified otherwise in a subrepository. See LGPLv2.0.txt.