CircuitPlayground Express Current Logger

boot.py

# boot.py
# Set Circuit Playground Express flash chip to program writeable 
#   If toggle switch is right, 
#      flash is program writeable and file access is frozen
#   If toggle switch is left,
#      flash chip file access ok, file writes give an error
# via Dan Conley 
#   https://learn.adafruit.com/cpu-temperature-logging-with-circuit-python/
#   writing-to-the-filesystem
# 2018 Mike Barela for Getting Started with Circuit Playground Express
import storage
from adafruit_circuitplayground.express import cpx

storage.remount("/", cpx.switch)

file_handler.py

"""
File based message handler for CircuitPython logging.
 
Adafruit invests time and resources providing this open source code.
Please support Adafruit and open source hardware by purchasing
products from Adafruit!
 
Written by Dave Astels for Adafruit Industries
Copyright (c) 2018 Adafruit Industries
Licensed under the MIT license.
 
All text above must be included in any redistribution.
"""
 
#pylint:disable=missing-super-argument
 
# Example:
#
#
# from file_handler import FileHandler
# import adafruit_logging as logging
# l = logging.getLogger('file')
# l.addHandler(FileHandler('log.txt'))
# l.level = logging.ERROR
# l.error("test")
 
from adafruit_logging import LoggingHandler
from adafruit_circuitplayground.express import cpx
import time

class FileHandler(LoggingHandler):
 
    def __init__(self, filename):
        """Create an instance.
 
        :param filename: the name of the file to which to write messages
 
        """
        self._filename = filename
        self._log_buffer = []
        # Clear the file and add the header
        with open(filename, 'w') as f:
            f.write("Time (s), Current (mA)\n")
 
    def format(self, level, msg):
        """Generate a string to log.
 
        :param level: The level at which to log
        :param msg: The core message
 
        """
        return str(time.monotonic()) + "," + str(msg) + "\n"
 
    def emit(self, level, msg):
        """Generate the message and write it to the File.
 
        :param level: The level at which to log
        :param msg: The core message
 
        """
        if len(self._log_buffer) == 10:
            try:
                with open(self._filename, 'a') as f:
                    while len(self._log_buffer) > 0:
                        f.write(self._log_buffer.pop(0))
            except OSError as e:
                # set NeoPixel 1 off and blink NeoPixel 0 (status) depending on 
                # the OS error
                cpx.pixels[1] = (0, 0, 0)           # Blank NeoPixel 1
                message_color = (99, 0, 0)          # Red for generic problem
                if e.args[0] == 28:                 # Device out of space
                    message_color = (228, 160, 40)  # set to Orange
                elif e.args[0] == 30:               # Device is read only
                    message_color = (181,  90,  0)  # set to Yellow
                for x in range(1, 10):              # Flash message 10 seconds
                    cpx.pixels[0] = message_color
                    time.sleep(1)
                    cpx.pixels[0] = (0, 0, 0)
                    time.sleep(1)
        else:
            self._log_buffer.append(self.format(level, msg))

main.py

import time
import board
from adafruit_ina260 import INA260, Mode
from adafruit_circuitplayground.express import cpx
from adafruit_debouncer import Debouncer
from file_handler import FileHandler
import adafruit_logging

i2c = board.I2C()
ina260 = INA260(i2c)
max_i = .0

btn_a = Debouncer(cpx._a)
btn_b = Debouncer(cpx._b)
if cpx.switch:
    # Green = Writable
    cpx.pixels[9] = (0, 1, 0)
else:
    # Red = Read-Only
    cpx.pixels[9] = (1, 0, 0)

logging = False
if not cpx.switch:
    l = adafruit_logging.getLogger('file')
    l.addHandler(FileHandler('current_log.csv'))
    l.level = adafruit_logging.INFO

while True:
    btn_a.update()
    if btn_a.fell and not logging:
        cpx.red_led = True
        logging = True

    btn_b.update()
    if btn_b.fell and logging:
        cpx.red_led = False
        logging = False

    if logging:    
        ina260.mode = Mode.TRIGGERED
        i = ina260.current
        if not cpx.switch:
            # Write to CSV
            l.info("%.4f" % i)
        else:
            # Use Mu Plotter
            print((i, max_i, time.monotonic()))

        if i > max_i:
            max_i = i
        
        #time.sleep(0.001)