Loam is part of the Magma ecosystem of python programming tools for FPGAs.
Magma is a programming model for building hardware. The main abstraction in Magma is a Circuit. Circuits are created and then wired together. Magma circuits can be saved as structural verilog files.
Mantle is a library of useful circuits. Examples of mantle circuits are logic operators, arithmetic operators, comparison operators, multiplexers, decoders and encoders, flip-flops, registers, counters, shift regiseters and memory.
Loam extends Magma to model FPGAs, Peripherals, Parts and Boards. A part represents an IC and a board a PCB. Parts and boards are themselves circuits. Parts can be wired to other parts, and boards consist of a collection of parts and headers. Just like parts, boards can be wired together via their headers. Loam makes it easy to build applications on a variety of different FPGA demonstration boards.
FPGAs are a subclass of parts. Circuits can be created on an FPGAs using Magma. A special feature of loam are peripherals. Peripherals make it easy to instantiate hardware drivers on an FPGA for a part connected to the FPGA.
Loam implementations of boards are expected to implement drivers for all the parts on the board. For example, a Lattice Icestick board contains an Lattice ice40 FPGA, an FTDI USART, LEDS, and 3 headers. The IceStick board contains built-in drivers for the USART and LEDs. This makes it very easy to build an application running on a particular board.
For example, here is a complete application to blink an LED on the IceStick.
from magma import wire, EndDefine
from mantle import Counter
from loam.boards.icestick import IceStick
# Create an instance of an IceStick board
icestick = IceStick()
# Turn on the Clock peripheral
# The clock is turned on because we are using a synchronous counter
icestick.Clock.on()
# Turn on the LED D5, also a peripheral
icestick.D5.on()
# Define a Magma Circuit on the FPGA on the IceStick
main = icestick.DefineMain()
# Create a 22-bit counter
N = 22
counter = Counter(N)
# Wire bit 21 of the counter to D5.
# Since the clock frequency is 12Mhz,
# bit 22 will toggle approximately once per second
wire(counter.O[N-1], main.D5)
EndDefine()This application is contained in the file blink.py.
blink.py is compiled to verilog using magma.
$ magma -b icestick blink.py
The verilog (.v) and physical constraint files (.pcf) can then be compiled to a bitstream file using the open source yosys tool chain
$ cd build
$ make
yosys -q -p 'synth_ice40 -top main -blif blink.blif' blink.v
arachne-pnr -q -d 1k -o blink.txt -p blink.pcf blink.blif
icepack blink.txt blink.bin
Finally, we upload to the board using the open source icestorm tools.
$ make upload
iceprog blink.bin
...
It is that easy to make an LED blink using an FPGA!
$ git clone https://github.com/phanrahan/loam
$ cd loam
Install the Python dependencies. You can do this automatically using pip
$ pip install -r requirements.txt
Or manually
- Follow these instructions to install magma
- Follow these instructions to install mantle
Install the pytest testing framework and the loam package, then run the test suite
to check that everything is in order.
$ pip install pytest
$ pip install -e .
$ ./scripts/run_tests.sh
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