CAN bit time calculation

bit_time.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
#
# Copyright (c) 2015 Kevin Laeufer <kevin.laeufer@rwth-aachen.de>

# bite_time.py

class UserSettings(object):
	def __init__(self, clk, bitrate, sampling_point, max_tolerance=0.02):
		self.clk = clk
		self.bitrate = bitrate
		self.sampling_point = sampling_point
		self.max_tolerance = max_tolerance

	def __str__(self):
		lines = [
			"CLK: {}MHz".format(float(self.clk) / 1000 / 1000),
			"Bitrate: {}kHz".format(float(self.bitrate) / 1000),
			"Desired Sampling Point: {:.5%}".format(self.sampling_point),
			"Max Tolerance: {:.5%}".format(self.max_tolerance)]
		return "\n".join(lines)


class ParameterSet(object):
	def __init__(self, bs1, bs2):
		self.bs1 = bs1
		self.bs2 = bs2

	@property
	def bitlength(self):
		return 1 + self.bs1 + self.bs2

	@property
	def sampling_point(self):
		return (1 + self.bs1) / (1 + self.bs1 + self.bs2)

	def prescaler(self, settings):
		return float(settings.clk) / float(settings.bitrate) / float(self.bitlength)

	def is_integer_prescaler(self, settings):
		return self.prescaler(settings).is_integer()

	def get_sampling_point_tolerance(self, settings):
		return abs(self.sampling_point - settings.sampling_point)

	def __str__(self):
		lines = [
			"BS1: {}".format(self.bs1),
			"BS2: {}".format(self.bs2),
			"Sampling Point: {:.5%}".format(self.sampling_point)]
		return "\n".join(lines)

if __name__ == "__main__":
	# generate all possible parametersets
	parameters = []
	for bs1 in reversed(range(1,17)):
		for bs2 in reversed(range(1,9)):
			parameters.append(ParameterSet(bs1, bs2))

	# create user settings
	settings = UserSettings(
		clk     = 8 * 1000 * 1000,
		bitrate = 125 * 1000,
		sampling_point = 0.7333)

	print(settings)

	# find best parameter set
	best = min(
		(ps for ps in parameters if ps.is_integer_prescaler(settings)),
		key=lambda ps: ps.get_sampling_point_tolerance(settings))

	print(best)