Steps for Hello World Microwatt ls2 for fpga/boards

Install Instructions

# devscripts
git clone
cd dev-env-setup
sudo bash
./mk-deb-chroot ls2-hello-world
./cp-scripts-to-chroot ls2-hello-world
exit # back to user

schroot -c ls2-hello-world
sudo bash # helps define SUDO_USER in new chroot
cd ~/dev-env-setup

# install dependencies in new chroot

# if you intend to upload fpga bitstreams in the same chroot, also need
# the fpga utilities

cd ~/src

# make hello_world.bin from microwatt
cd tercel-qspi/
cd hello_world/
cp hello_world.bin ../../ls2
cd ../..

# make the Libre-SOC core (for external use)
cd soc
make microwatt_external_core
cp external_core_top.v ../ls2

# check out ls2 peripheral framework
cd ../ls2
git checkout 426e2d9585cd4b1fb96a38987f97878285ee5ba7

export PATH=/usr/local/nextpnr-xilinx/bin:$PATH
export XRAY_DIR=/usr/local/nextpnr-xilinx

# plug in FPGA board (Arty A7-100t, VERSA_ECP5, other)
# run in 2nd terminal "minicom -D /dev/ttyUSB1"

python3 src/ arty_a7 hello_world.bin    # for Arty A7-100t
python3 src/ versa_ecp5 hello_world.bin # (for a VERSA_ECP5)

This directly programs a tmp bitstream using xc3sprog to nexys4 board. If needed modify sources to produce a fixed file bitstream and

copy build/top.bit to board/server (scp, rsync)
minicom -D /dev/ttyUSB1
xc3sprog -c nexys4 top.bit

If there are multiple Arty-A7-100t boards connected you need to know the serial number (lsusb | grep Serial)

xc3sprog -c nexys4 -s {insert_full_serial_number} top.bit

Using ls2 with microwatt

This is doable but tricky. An older version is required at present.

git clone
git checkout microwatt_verilator
make microwatt.v

From there, some hand-editing is required. search for core_NNNNNNN_XXX_YYY and rename it to external_core_top. Save the file as external_core_top.v and it can be used in place of the Libre-SOC Core, above.

In fact any core can be used with ls, as long as it is compliant with the interfaces. Both Wishbone Interfaces must be WB4 Pipeline compliant (proper stall handling) or the stall signal faked externally with a wrapper: stall=stb&~ack

Using ls2 with verilator

first you need to build hello_world (or any other firmware) to start at 0xff000000. Then you can run build ls.v using that firmware:

python3 src/ sim /tmp/ff000000_hw.bin

The output of that command is:

platform sim /tmp/ff000000_hw.bin None
fpga sim firmware /tmp/ff000000_hw.bin
ddr pins None
spiflash pins None
ethmac pins None
hyperram pins [<lambdasoc.periph.hyperram.HyperRAMPads object at 0x735e9940dd30>]
fw at address ff000000
SRAM 0x8000 at address 0x0

To use verilator, make sure to run the devscript:


And set the GHDLSYNTH and update PATH:

export PATH=/usr/local/verilator/bin:$PATH
export GHDLSYNTH=ghdl

After that you can compile microwatt-verilator:

export FPGA_TARGET=verilator
make microwatt-verilator

Estimating transistor count using yosys

Use yosys to run synthesis and using stat to view gate/transistor count:

cd src/ls2/
yosys> read_verilog ls2.v external_core_top.v ../uart16550/rtl/verilog/*.v
yosys> synth
yosys> tee -a stat_cmos.log stat -tech cmos

Then you can view the resulting log file afterwards. Bare in mind synth will probably take a while. TODO: Find multi-threaded option