MicroPython I2C PCF8591 round value problem Raspberry Pi Pico

[achim]

Hallo
Leider in Deutsch.
Schliesse den PCF8591 mit dem I2C Bus an einen Paspberry Pi Pico und Micropython (ESP32) an. Der PCF wird erkannt und Daten ausgelesen. Es wird aber nur 64, 128 und 192 dargestellt. Alle Zwischenwerte werden nicht erkannt. Es wird wahrscheinlich nur B7 und B6 gelesen. Kann aber keinen Grund dazu finden.
achim

Ciao,
Purtroppo, in tedesco:
Collega il PCF8591 al bus I2C di un Raspberry Pi Pico e a Micropython (ESP32). Il PCF viene riconosciuto e i dati vengono letti. Tuttavia, vengono visualizzati solo 64, 128 e 192. Tutti i valori intermedi non vengono riconosciuti. Probabilmente vengono letti solo B7 e B6. Non riesco però a trovare una ragione specifica.
Achim

[Renzo Mischianti]

Please, can you reupload the file.
Thanks

[achim]

#
# PCF8591 Analog GPIO Port Expand
#
# AUTHOR:  Renzo Mischianti
# Website: www.mischianti.org
# VERSION: 0.0.1
#
# Description:
# This script read one channel for time of pcf8591
#
#            +---------------+
#  AIN0 (1)  | * 1    U   16 |  VDD
#  AIN1 (2)  | * 2        15 |  AOUT
#  AIN2 (3)  | * 3        14 |  VREF
#  AIN3 (4)  | * 4        13 |  AGND
#    A0 (5)  | * 5        12 |  EXT
#    A1 (6)  | * 6        11 |  OSC
#    A2 (7)  | * 7        10 |  SCL
#   VSS (8)  | * 8         9 |  SDA
#            +---------------+
#
# AIN0: Analog input channel 0
# AIN1: Analog input channel 1
# AIN2: Analog input channel 2
# AIN3: Analog input channel 3
# A0: Address input 0
# A1: Address input 1
# A2: Address input 2
# VSS: Ground
# SDA: Serial data line (I2C)
# SCL: Serial clock line (I2C)
# OSC: Oscillator output
# EXT: External trigger input
# AGND: Analog ground
# VREF: Voltage reference input
# AOUT: Analog output
# VDD: Power supply
#
# Porting of PCF8591 library for Arduino
# http://mischianti.org/pcf8591-i2c-analog-i-o-expander/
#

from machine import I2C, Pin
from PCF8591 import PCF8591
import utime

# Initialize the I2C bus
i2c = I2C(0, scl=Pin(21), sda=Pin(20))  # Adjust the pins and frequency as needed for your board

# Initialize the PCF8591
pcf8591 = PCF8591(0x48, i2c)  # Adjust the address if needed
if pcf8591.begin():
    print("PCF8591 found")

print("AIN0 ", pcf8591.analog_read(PCF8591.AIN0))  # You can use PCF8591.CHANNEL_0
print("AIN1 ", pcf8591.analog_read(PCF8591.AIN1))
print("AIN2 ", pcf8591.analog_read(PCF8591.AIN2))
print("AIN3 ", pcf8591.analog_read(PCF8591.AIN3))

Das ist der gesamte Code. Es wird nur 0, 64, 128 oder 192 ausgegeben

[Renzo Mischianti]

Probably I undestand, can you try with analog_read_all?
Thanks Renzo

[achim]

#
# PCF8591 Analog GPIO Port Expand
#
# AUTHOR:  Renzo Mischianti
# Website: www.mischianti.org
# VERSION: 0.0.1
#
#
# Porting of PCF8591 library for Arduino
# http://mischianti.org/pcf8591-i2c-analog-i-o-expander/
#
#            +---------------+
#  AIN0 (1)  | * 1    U   16 |  VDD
#  AIN1 (2)  | * 2        15 |  AOUT
#  AIN2 (3)  | * 3        14 |  VREF
#  AIN3 (4)  | * 4        13 |  AGND
#    A0 (5)  | * 5        12 |  EXT
#    A1 (6)  | * 6        11 |  OSC
#    A2 (7)  | * 7        10 |  SCL
#   VSS (8)  | * 8         9 |  SDA
#            +---------------+
#
# AIN0: Analog input channel 0
# AIN1: Analog input channel 1
# AIN2: Analog input channel 2
# AIN3: Analog input channel 3
# A0: Address input 0
# A1: Address input 1
# A2: Address input 2
# VSS: Ground
# SDA: Serial data line (I2C)
# SCL: Serial clock line (I2C)
# OSC: Oscillator output
# EXT: External trigger input
# AGND: Analog ground
# VREF: Voltage reference input
# AOUT: Analog output
# VDD: Power supply
#
#
# The MIT License (MIT)
#
# Copyright (c) 2017 Renzo Mischianti www.mischianti.org All right reserved.
#
# You may copy, alter and reuse this code in any way you like, but please leave
# reference to www.mischianti.org in your comments if you redistribute this code.
#
# 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.
#

import utime
from machine import I2C, Pin

# AIN0 = CHANNEL0 = 0b00000000
# AIN1 = CHANNEL1 = 0b00000001
# AIN2 = CHANNEL2 = 0b00000010
# AIN3 = CHANNEL3 = 0b00000011

class PCF8591:
    AIN0 = CHANNEL0 = 0b00000000
    AIN1 = CHANNEL1 = 0b00000001
    AIN2 = CHANNEL2 = 0b00000010
    AIN3 = CHANNEL3 = 0b00000011

    AUTOINCREMENT_READ = 0b00000100

    SINGLE_ENDED_INPUT = 0b00000000
    TREE_DIFFERENTIAL_INPUT = 0b00010000
    TWO_SINGLE_ONE_DIFFERENTIAL_INPUT = 0b00100000
    TWO_DIFFERENTIAL_INPUT = 0b00110000

    ENABLE_OUTPUT = 0b01000000
    DISABLE_OUTPUT = 0b00000000

    OUTPUT_MASK = 0b01000000

    def __init__(self, address, i2c=None, i2c_id=0, sda=None, scl=None):
        if i2c:
            self._i2c = i2c
        elif sda and scl:
            self._i2c = I2C(i2c_id, scl=Pin(scl), sda=Pin(sda))
        else:
            raise ValueError('Either i2c or sda and scl must be provided')

        self._address = address
        self._output_status = self.DISABLE_OUTPUT  # default
        
    # Kontrolle ob Slave vorhanden ist
    def begin(self):
        if self._i2c.scan().count(self._address) == 0:
            # raise OSError('PCF8591 not found at I2C address {:#x}'.format(self._address))
            return False # Slave nicht vorhanden
        else:
            return True # Slave vorhanden

    def analog_read_all(self, read_type=SINGLE_ENDED_INPUT):
        operation = self.AUTOINCREMENT_READ | read_type | (self._output_status & self.OUTPUT_MASK)
        self._i2c.writeto(self._address, bytearray([operation]))
        utime.sleep_ms(1)
        # data = self._i2c.readfrom(self._address, 5)
        data = []
        self._i2c.readfrom(self._address, 1)
        data.append(int.from_bytes(self._i2c.readfrom(self._address, 1), "big"))
        data.append(int.from_bytes(self._i2c.readfrom(self._address, 1), 'big'))
        data.append(int.from_bytes(self._i2c.readfrom(self._address, 1), 'big'))
        data.append(int.from_bytes(self._i2c.readfrom(self._address, 1), 'big'))

        return data[0], data[1], data[2], data[3]

    def analog_read(self, channel, read_type = SINGLE_ENDED_INPUT):
        operation = channel | read_type | (self._output_status & self.OUTPUT_MASK)
        self._i2c.writeto(self._address, bytearray([operation]))
        utime.sleep_ms(1)
        data = self._i2c.readfrom(self._address, 2)
        return data[1]

    #def voltage_read(self, channel, reference_voltage=3.3):
    def voltage_read(self, channel, reference_voltage=5.0):    
        voltage_ref = reference_voltage
        ana = self.analog_read(channel, self.SINGLE_ENDED_INPUT)
        return ana * voltage_ref / 255

    def voltage_write(self, value, reference_voltage=3.3):
        ana = value * 255 / reference_voltage
        self.analog_write(ana)

    def analog_write(self, value):
        if value > 255 or value < 0:
            Exception('Value must be between 0 and 255')

        self._output_status = self.ENABLE_OUTPUT

        self._i2c.writeto(self._address, bytearray([self.ENABLE_OUTPUT, value]))

    def disable_output(self):
        self._output_status = self.DISABLE_OUTPUT

        self._i2c.writeto(self._address, bytearray([self.DISABLE_OUTPUT]))

Damit wird nur A0 angezeigt, A1, A2 und A3 fehlen

[achim]

#
# PCF8591 Analog GPIO Port Expand
#
# AUTHOR:  Renzo Mischianti
# Website: www.mischianti.org
# VERSION: 0.0.1
#
# Description:
# This script read all analog input of pcf8591
#
#            +---------------+
#  AIN0 (1)  | * 1    U   16 |  VDD
#  AIN1 (2)  | * 2        15 |  AOUT
#  AIN2 (3)  | * 3        14 |  VREF
#  AIN3 (4)  | * 4        13 |  AGND
#    A0 (5)  | * 5        12 |  EXT
#    A1 (6)  | * 6        11 |  OSC
#    A2 (7)  | * 7        10 |  SCL
#   VSS (8)  | * 8         9 |  SDA
#            +---------------+
#
# AIN0: Analog input channel 0
# AIN1: Analog input channel 1
# AIN2: Analog input channel 2
# AIN3: Analog input channel 3
# A0: Address input 0
# A1: Address input 1
# A2: Address input 2
# VSS: Ground
# SDA: Serial data line (I2C)
# SCL: Serial clock line (I2C)
# OSC: Oscillator output
# EXT: External trigger input
# AGND: Analog ground
# VREF: Voltage reference input
# AOUT: Analog output
# VDD: Power supply
#
# Porting of PCF8591 library for Arduino
# http://mischianti.org/pcf8591-i2c-analog-i-o-expander/
#

from machine import I2C, Pin
import utime
from PCF8591 import PCF8591 
# Initialize the I2C bus
i2c = I2C(0, scl=Pin(21), sda=Pin(20))  # Adjust the pins and frequency as needed for your board

# Initialize the PCF8591
pcf8591 = PCF8591(0x48, i2c)  # Adjust the address if needed
if pcf8591.begin():
    print("PCF8591 found")

# Main loop
while True:
    # Read all analog input channels
    ain0, ain1, ain2, ain3 = pcf8591.analog_read_all()

    # Print the results
    print("AIN0:", ain0, "AIN1:", ain1, "AIN2:", ain2, "AIN3:", ain3)

    # Wait for 1 second
    utime.sleep(1)

Ist dieser Code

[Renzo Mischianti]

Can you post the REPL console output.
Thanks RM

[Renzo Mischianti]

Hi,
I redo all the tests if you get the library from pip

pip install pcf8591-library

Bye Renzo

[achim]

Wie kann ich eine pip installieren wenn ich mit Micropython auf dem Raspberry Pi Pico arbeite. Ist kein Raspberry.

How can I install pip when working with MicroPython on the Raspberry Pi Pico? It’s not a Raspberry Pi.

[Renzo Mischianti]

What IDE do you use?

[jiangzhiyu233]

Hello!
I encountered the same problem, although I used the updated version 0.02, it seems that the situation has not changed: my pcf8591 still only reads three values ​​​​64, 128, 192. The microcontroller is a Raspberry Pi pico w, Using micropython and ThonyyIDE, is there any solution? Thank you so much

[jiangzhiyu233]

The AOUT port is good, analog/voltage write can output correct value, but there are some problem with the analog/voltage reading of all AIN port.

[Renzo Mischianti]

Hi jiangzhiyu233,
I retry the code and I don’t have that behavior, do you use the example provided in github??
Bye Renzo

[jiangzhiyu233]

Ahh, I did not directly test with the example in github. I used this library in my project and find some problem. And wrote a small program to test:

from machine import I2C, Pin
from PCF8591 import PCF8591

i2c = I2C(0, scl=Pin(9), sda=Pin(8)) 

pcf8591 = PCF8591(0x48, i2c)

if not pcf8591.begin():
    print("PCF8591 not found")
else:
    with open('test.txt', 'w') as file:
        for value in range(256):
            pcf8591.analog_write(value)
            utime.sleep_ms(10)  
            read_value = pcf8591.analog_read(pcf8591.AIN0)  
            file.write(f"{value}, {read_value}\n")
            print(f"Written: {value}, Read: {read_value}")
            utime.sleep_ms(10)

    print("TEST FINISHED")

And part of result:

Written: 49, Read: 128
Written: 50, Read: 128
Written: 51, Read: 128
Written: 52, Read: 128
Written: 53, Read: 128
Written: 54, Read: 128
Written: 55, Read: 128
Written: 56, Read: 128
Written: 57, Read: 128
Written: 58, Read: 128
Written: 59, Read: 128
Written: 60, Read: 128
Written: 61, Read: 128
Written: 62, Read: 128
Written: 63, Read: 128
Written: 64, Read: 128

During the test, I connected the AOUT and AIN0 ports and no error in wiring. And when the read and write functions are tested separately(both analog and voltage), the oscilloscope can also see the changes in the AOUT port. However, the AIN port cannot correctly read the waveform generated by another function generator.
I also tried whether it was a problem with the Raspberry Pi pico, but when I connected the AOUT port of the PCF8591 to the pico’s internal AD converter, it could read the changes in the waveform normally.
If there is no problem with the program, maybe there is some conflict in the hardware? Between PCF8591 and Raspberry Pi picow ?

[Renzo Mischianti]

Hi jiangzhiyu233,
I executed your code and I replicated the issue. It seems that there are some problems when writing and reading at the same time.
I do a little fix, try It, and give me feedback.
Thanks Renzo

[jiangzhiyu233]

Hello Renzo!
I tried running the modified library (and also tried it on another set of Raspberry Pi picow and PCF8591). PCF8591 still couldn’t correctly read the value which generated by itself, but the value it read are not fixed now.
Here is the result:

Written: 0, Read: 128
Written: 1, Read: 184
Written: 2, Read: 184
Written: 3, Read: 184
Written: 4, Read: 0
Written: 5, Read: 0
Written: 6, Read: 0
Written: 7, Read: 0
Written: 8, Read: 128
Written: 9, Read: 184
Written: 10, Read: 0
Written: 11, Read: 184
Written: 12, Read: 0
Written: 13, Read: 0
Written: 14, Read: 184
Written: 15, Read: 0
Written: 16, Read: 0
Written: 17, Read: 0
Written: 18, Read: 0
Written: 19, Read: 184
Written: 20, Read: 0
Written: 21, Read: 128
Written: 22, Read: 184
Written: 23, Read: 0
Written: 24, Read: 0
Written: 25, Read: 0
Written: 26, Read: 184
Written: 27, Read: 184
Written: 28, Read: 0
Written: 29, Read: 184
Written: 30, Read: 184
Written: 31, Read: 0
Written: 32, Read: 184
Written: 33, Read: 0
Written: 34, Read: 0
Written: 35, Read: 0
Written: 36, Read: 0
Written: 37, Read: 0
Written: 38, Read: 0
Written: 39, Read: 184
Written: 40, Read: 184
Written: 41, Read: 0
Written: 42, Read: 128
Written: 43, Read: 0
Written: 44, Read: 184
Written: 45, Read: 0
Written: 46, Read: 0
Written: 47, Read: 0
Written: 48, Read: 184
Written: 49, Read: 0
Written: 50, Read: 0
Written: 51, Read: 0
Written: 52, Read: 0
Written: 53, Read: 0
Written: 54, Read: 0
Written: 55, Read: 0
Written: 56, Read: 184
Written: 57, Read: 0
Written: 58, Read: 184
Written: 59, Read: 0
Written: 60, Read: 0
Written: 61, Read: 0
Written: 62, Read: 184
Written: 63, Read: 184
Written: 64, Read: 184
Written: 65, Read: 128
Written: 66, Read: 184
Written: 67, Read: 0
Written: 68, Read: 184
Written: 69, Read: 0
Written: 70, Read: 184
Written: 71, Read: 128
Written: 72, Read: 184
Written: 73, Read: 128
Written: 74, Read: 0
Written: 75, Read: 0
Written: 76, Read: 0
Written: 77, Read: 184
Written: 78, Read: 184
Written: 79, Read: 0
Written: 80, Read: 0
Written: 81, Read: 0
Written: 82, Read: 0
Written: 83, Read: 0
Written: 84, Read: 0
Written: 85, Read: 0
Written: 86, Read: 0
Written: 87, Read: 184
Written: 88, Read: 0
Written: 89, Read: 184
Written: 90, Read: 0
Written: 91, Read: 0
Written: 92, Read: 0
Written: 93, Read: 0
Written: 94, Read: 0
Written: 95, Read: 0
Written: 96, Read: 184
Written: 97, Read: 184
Written: 98, Read: 184
Written: 99, Read: 0
Written: 100, Read: 128
Written: 101, Read: 184
Written: 102, Read: 0
Written: 103, Read: 0
Written: 104, Read: 184
Written: 105, Read: 128
Written: 106, Read: 0
Written: 107, Read: 184
Written: 108, Read: 0
Written: 109, Read: 0
Written: 110, Read: 0
Written: 111, Read: 128
Written: 112, Read: 0
Written: 113, Read: 184
Written: 114, Read: 184
Written: 115, Read: 0
Written: 116, Read: 128
Written: 117, Read: 184
Written: 118, Read: 128
Written: 119, Read: 0
Written: 120, Read: 184
Written: 121, Read: 184
Written: 122, Read: 184
Written: 123, Read: 0
Written: 124, Read: 0
Written: 125, Read: 184
Written: 126, Read: 128
Written: 127, Read: 184
Written: 128, Read: 0
Written: 129, Read: 0
Written: 130, Read: 184
Written: 131, Read: 0
Written: 132, Read: 0
Written: 133, Read: 0
Written: 134, Read: 0
Written: 135, Read: 0
Written: 136, Read: 184
Written: 137, Read: 0
Written: 138, Read: 0
Written: 139, Read: 0
Written: 140, Read: 0
Written: 141, Read: 184
Written: 142, Read: 128
Written: 143, Read: 0
Written: 144, Read: 184
Written: 145, Read: 184
Written: 146, Read: 184
Written: 147, Read: 0
Written: 148, Read: 0
Written: 149, Read: 0
Written: 150, Read: 0
Written: 151, Read: 184
Written: 152, Read: 0
Written: 153, Read: 184
Written: 154, Read: 0
Written: 155, Read: 184
Written: 156, Read: 0
Written: 157, Read: 0
Written: 158, Read: 0
Written: 159, Read: 0
Written: 160, Read: 184
Written: 161, Read: 0
Written: 162, Read: 0
Written: 163, Read: 184
Written: 164, Read: 0
Written: 165, Read: 0
Written: 166, Read: 0
Written: 167, Read: 0
Written: 168, Read: 0
Written: 169, Read: 184
Written: 170, Read: 128
Written: 171, Read: 0
Written: 172, Read: 0
Written: 173, Read: 128
Written: 174, Read: 184
Written: 175, Read: 184
Written: 176, Read: 184
Written: 177, Read: 0
Written: 178, Read: 0
Written: 179, Read: 184
Written: 180, Read: 0
Written: 181, Read: 184
Written: 182, Read: 184
Written: 183, Read: 0
Written: 184, Read: 0
Written: 185, Read: 128
Written: 186, Read: 0
Written: 187, Read: 128
Written: 188, Read: 0
Written: 189, Read: 128
<strong>Written: 190, Read: 189</strong>
Written: 191, Read: 128
<strong>Written: 192, Read: 192</strong>
Written: 193, Read: 128
Written: 194, Read: 128
Written: 195, Read: 0
Written: 196, Read: 128
<strong>Written: 197, Read: 196</strong>
Written: 198, Read: 128
Written: 199, Read: 0
<strong>Written: 200, Read: 198</strong>
Written: 201, Read: 128
Written: 202, Read: 0
Written: 203, Read: 128
Written: 204, Read: 0
Written: 205, Read: 128
Written: 206, Read: 0
Written: 207, Read: 128
Written: 208, Read: 0
Written: 209, Read: 128
Written: 210, Read: 0
Written: 211, Read: 0
Written: 212, Read: 128
Written: 213, Read: 0
Written: 214, Read: 128
Written: 215, Read: 0
<strong>Written: 216, Read: 213
Written: 217, Read: 214</strong>
Written: 218, Read: 128
<strong>Written: 219, Read: 216
Written: 220, Read: 217</strong>
Written: 221, Read: 0
<strong>Written: 222, Read: 219</strong>
Written: 223, Read: 128
Written: 224, Read: 0
<strong>Written: 225, Read: 221</strong>
Written: 226, Read: 0
Written: 227, Read: 128
<strong>Written: 228, Read: 224</strong>
Written: 229, Read: 128
<strong>Written: 230, Read: 226</strong>
Written: 231, Read: 128
Written: 232, Read: 128
<strong>Written: 233, Read: 228
Written: 234, Read: 229
Written: 235, Read: 230</strong>
Written: 236, Read: 0
Written: 237, Read: 128
<strong>Written: 238, Read: 232</strong>
Written: 239, Read: 128
<strong>Written: 240, Read: 233
Written: 241, Read: 233</strong>
Written: 242, Read: 128
Written: 243, Read: 0
Written: 244, Read: 0
Written: 245, Read: 0
Written: 246, Read: 0
Written: 247, Read: 0
Written: 248, Read: 0
Written: 249, Read: 0
<strong>Written: 250, Read: 234</strong>
Written: 251, Read: 0
Written: 252, Read: 0
Written: 253, Read: 128
<strong>Written: 254, Read: 234</strong>
Written: 255, Read: 234

When the value read by analog_read is greater than 184 (sometimes change a little), PCF8591 will read correctly from time to time (I marked it; and the AIN port can only read a maximum of 233 or 234), but most of the time it is still 0 or 128 . When the number read by the AIN port is less than 184, it will only read 0, 128 or 184 (I think 184 should be when PCF8591 tries to read ‘correctly’). The waveform of the AOUT port can still be read normally by the oscilloscope.

[Author]

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