#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Fri Jan 18 22:30:00 2019

@author: oyvind
"""
import math
import matplotlib.pyplot as plt

# Name for the saved graph
filename = "4b"

# RPM
RPM = 40000
Hz = RPM / 60

# Tau in microseconds
tau = 1/(2 * Hz) * 10**6

# Square wave freq in kHz
sqWFreq = 5

# How many taus you want
periods = 3



# The resolution of each tau
resolution = 1000

# Forwardvoltage of diode
diodeVoltage = 0.7

# Calculates the length of each squarewave in taus
sqTime = (1/sqWFreq) * 10**3
sqTau = sqTime / tau

# Creats the  square wave
# Default values are in the argument list
def CreateSquareWave(amp=2.5, offset=2.5, symetry=0.5):
    squareWave = []
    # Only generates as many datapoints we need
    while len(squareWave) < periods * resolution:
        # First generate the first half
        for r in range(int(resolution*sqTau * symetry)):
            squareWave.append(amp + offset)
        # Then the second
        for r in range(int(resolution*sqTau * (1 - symetry))):
            squareWave.append(offset - amp)
    squareWave = squareWave[:(resolution*periods)]
    return squareWave


# Generate all the time-ticks
def GenerateTime():
    times = []
    for t in range(periods * resolution):
        times.append(t/resolution)
    print(len(times))
    return(times)
    

def CapVoltage(wave, times):
    cP = wave[0] # Start voltage-supply
    v0 = 0 # Start voltage
    cT = 0 #Start time
    volt = []
    for p in range(len(wave)):
        # If the voltage-supply changes, recalculate startvalues
        if wave[p] != cP:
            v0 = volt[-1] # New start voltage, uses the last voltage calculated
            if wave[p] == 0:
                v0 = diodeVoltage
            cP = wave[p] # Variable so the array is not accessed.
            cT = times[p] # Offset time for each period
        # Calculate the voltage over the CAPACITOR with the start values
        volt.append(cP + (v0 - cP) * math.exp(-(times[p] - cT)))
    return(volt)
        
        
SquareWave = CreateSquareWave()
time = GenerateTime()
CapWave = CapVoltage(SquareWave, time)

plt.figure(figsize=(15,5))
plt.plot(time, SquareWave, time, CapWave)
plt.xlabel("Time [τ]")
plt.ylabel("Voltage [V]")
plt.legend(["Supply voltage", "Capacitor voltage"], loc="lower right")
plt.savefig(filename + ".png", dpi = 300)
plt.show()