pico PIO frequency reader

picoFreq.py

'''
 *
 *
 * The MIT License (MIT)
 *
 * Copyright (c) 2023 Daniel Perron
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
'''

''' this is a program to read the duration of the high pulse in micro-second '''

from rp2 import PIO, asm_pio
from machine import Pin, mem32
import math
import utime


@asm_pio()
def FREQ_TRIGGER_PIO():
    set(x,0)
    label('loopH1')
    jmp(x_dec,'loopH2')
    label('loopH2')
    nop()
    nop()
    jmp( pin, 'loopH1')
    mov(isr,x)
    push()
    set(x,0)
    label('loopH3')
    jmp(x_dec,'loopH4')
    label('loopH4')
    nop()
    jmp( pin, 'loopH1')
    jmp( 'loopH3')



print("start")
thePin = machine.Pin(14,Pin.IN,Pin.PULL_UP)
clock = 125_000_000
sm = rp2.StateMachine(0)
sm.init(FREQ_TRIGGER_PIO, freq=clock,
        in_base = thePin, jmp_pin = thePin)
sm.active(1)


count =0

#clean first delay
sm.get()
sm.get()

sum=0.0
sumSquare=0.0
freqMin = 120.0
freqMax = 0.0


while count<3600:
    freq = (clock / 4)/(0xfffffffe - sm.get())
    if freq>freqMax:
        freqMax=freq
    if freq<freqMin:
        freqMin=freq
    sum+= freq
    sumSquare += (freq * freq)
    count+=1

average= sum/count
sumOfVariance = sumSquare - ( sum * average)
stdev = math.sqrt(sumOfVariance / ( count -1))

print("Statistique de la ligne de puissance 60Hz sur ",count, " cycles")
print("moyenne (Hz): {:2.4f} +/- {:0.4f}".format(sum/count,stdev))
print("Minimum (Hz): ",freqMin)
print("Maximum (Hz): ",freqMax)