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RISC-V on Colorlight 5A-75B (v7.0)

Demo soft SoC (VexRiscv) built with LiteX on a Colorlight 5A-7B board (Lattice ECP5).

Current configuration

  • CPU runs at 198MHz with 32KB cache
  • 4MB SDRAM running at 66MHz
  • Gigabit ethernet PHY enabled with netboot support (not tested yet)
  • FPGA configuration is downloaded in RAM, no flash support yet

Introduction

This demo is based on litexOnColorlightLab004

  • I removed the relocated serial port, so no hardware modifications are needed
  • There is no LED and no User Button - both pins are used by the UART
name Pin note
clk25 P6 25MHz clock
cpu_reset --- (deleted)
user_led --- (deleted)
Uart TX U16 J19 (DATA_LED-)
Uart RX R16 J19 (KEY+)

Required hardware

  • STM32 - blue pill board repurposed as JTAG probe (see dirtyJTAG)
  • ColorLight has no on-board JTAG adapter, so user must solder a pinheader (J27 for JTAG signals, J33 for VCC and J34 for GND) and connect an external probe (see chubby75)
  • an USB <-> serial converter must be used to have access to serial interface

Software setup

Build

gateware (aka FPGA configuration)

Just:

./base.py --build

firmware (code that runs on the RISC-V CPU after boot)

cd firmware && make

see [lab004] for more details.

Load FPGA bitstream

./base.py --load --cable dirtyJtag

Load and run RISC-V firmware

lxterm /dev/ttyUSBx --speed 38400 --kernel firmware/firmware.bin

where ttyUSBx is your USB <-> UART converter device. Sometimes it is called /dev/ttyACMx.

This command runs a special serial terminal which waits for a magic string, then uploads the binary firmware/firmware.bin to the FPGA and runs it.

Note: The standard UART speed is 115200 bps, however because we are running the CPU at 3x the system clock the UART speed ends up being 115200/3 = 38400 bps

Boot screen

The following screen is captured with minicom. You can see the magic string output for the lxterm serial bootloader. The console is interactive, you can type 'help' for a list of commands.

        __   _ __      _  __
       / /  (_) /____ | |/_/
      / /__/ / __/ -_)>  <
     /____/_/\__/\__/_/|_|
   Build your hardware, easily!

 (c) Copyright 2012-2020 Enjoy-Digital
 (c) Copyright 2007-2015 M-Labs

 BIOS built on Jul 21 2020 03:27:32
 BIOS CRC passed (b5178a5a)

 Migen git sha1: 731c192
 LiteX git sha1: 63c19ff4

--=============== SoC ==================--
CPU:       VexRiscv @ 198MHz
BUS:       WISHBONE 32-bit @ 4GiB
CSR:       8-bit data
ROM:       32KiB
SRAM:      8KiB
L2:        32KiB
MAIN-RAM:  4096KiB

--========== Initialization ============--
Ethernet init...
Initializing DRAM @0x40000000...
SDRAM now under software control
SDRAM now under hardware control
Memtest at 0x40000000...
[########################################]
[########################################]
Memtest OK
Memspeed at 0x40000000...
Writes: 461 Mbps
Reads:  382 Mbps

--============== Boot ==================--
Booting from serial...
Press Q or ESC to abort boot completely.
sL5DdSMmkekro
Timeout
Booting from network...
Local IP : 192.168.1.50
Remote IP: 192.168.1.100
Booting from boot.json...
Booting from boot.bin...
Copying boot.bin to 0x40000000... 
Network boot failed.
No boot medium found

--============= Console ================--

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