icemu is a Python library that emulates integrated circuits at the logic level. For example,
if you want to simulate a circuit with a decoder driving the clock pin of two shift registers,
it would look like this:
dec = SN74HC138()
sr1 = CD74AC164()
sr2 = CD74AC164()
mcu_pin = OutputPin('PB4')
sr1.pin_CP.wire_to(dec.pin_Y0)
sr2.pin_CP.wire_to(dec.pin_Y1)
sr1.pin_DS1.wire_to(mcu_pin)
sr2.pin_DS1.wire_to(mcu_pin)
print(dec.asciiart())
_______
A>|- U +|>Y7
B>|- +|>Y6
C>|- +|>Y5
G2A>|- +|>Y4
G2B>|- +|>Y3
G1>|+ +|>Y2
Y0<|-___+|>Y1
You could then play with pins at your heart contents and have them "propagate" through wires and IC logic automatically.
Here's a little video of icemu used in my seg7-multiplex project:
This board drives an array of 7-segments displays through a ATtiny45 MCU and a couple of ICs to
drive down pin count. The software that runs on the MCU is real, but with a couple of ifdefs, can
run on a completely simulated environment with the help of icemu.
The goal of this library is to facilitate the testing and debugging of embedded software. When we run software on an embedded prototype, it's often hard to debug failures because we don't even know if the problem comes from hardware (wiring, it's always the wiring!) or software. Moreover, testing directly on a prototype often involves significant setup time.
With emulation, we have a quick setup time, introspection capabilities, all this stuff. We can then confirm the soundness of our logic before sending it to our prototype.
Because it's used for debugging purposes, speed is not essential. Also, Python is easy to glue with C.
I've tried writing quick icemu prototype in C and Rust, but they were needlessly complicated.
With Python, it's easy to write the software and add new chips. Because there's gonna be a lot
of these chips to add, we might as well make this process as fast as possible.
You can install icemu with pip on python 3.4+:
$ pip install --user icemu
Then, you need to recreate your prototype's logic in a small Python program that uses icemu and
wrap that into easy to use functions. Those functions should be designed to receive pin state
change from the MCU and apply the logic change into your circuit. Make that program print relevant
information so that you can assert your logic's soundness.
Then, write yourself a small Hardware Abstraction Layer at the pin/register level, embed your
Python program like a regular C application would do, make your ifdefed functions call helper
functions you've written in your Python program, compile and run!
You can find small examples is the tests folders, but the best way to get the grand idea is to
look at a project that uses it such as my seg7-multiplex or my
solar-timer. Read the Simulation part of the README to get started.
LGPLv3, Copyright 2017 Virgil Dupras