You can find updated version of documentation on my site​ PCF8591

Library to use i2c analog IC with arduino and esp8266. Can read analog value and write analog value with only 2 wire (perfect for ESP-01).

• 01/02/2024: v1.1.2 Add the possibility to insert address at begin() function
• 10/07/2023: v1.1.1 Add support for Arduino UNO R4
• 16/02/2023: v1.1.0
  • Fix STM32 support and add support for Raspberry Pi Pico and other rp2040 boards
  • Add support for custom SERCOM interface of Arduino SAMD devices. Force SDA SCL to use GPIO numeration for STM32 bug (https://www.mischianti.org/forums/topic/compatible-with-stm32duino/).
  • Force SDA SCL to use GPIO numeration (https://www.mischianti.org/forums/topic/cannot-set-sda-clk-on-esp8266/).
  • Fix the SDA SCL type #58 and add basic support for SAMD device.
• 06/04/2022: v1.0.2 Fix package size

Tutorial:

To download. click the DOWNLOADS button in the top right corner, rename the uncompressed folder PCF8591. Check that the PCF8591 folder contains PCF8591\\.cpp and PCF8591.h. Place the DHT library folder your <arduinosketchfolder>/libraries/ folder. You may need to create the libraries subfolder if its your first library. Restart the IDE.

Reef complete PCF8591 Analog input and analog output to digital converter with i2c bus.

I try to simplify the use of this IC, with a minimal set of operation.

Constructor: you must pas the address of i2c (to check the adress use this guide I2cScanner)

	PCF8591(uint8_t address);

for esp8266 if you want specify SDA e SCL pin use this:

	PCF8591(uint8_t address, uint8_t sda, uint8_t scl);

then IC as you can see in the image have 4 analog input and 1 analog output:

So to read all analog input in one trasmission you can do (the value is from 0 to 255):

	PCF8591::AnalogInput ai = pcf8591.analogReadAll();
	Serial.print(ai.ain0);
	Serial.print(" - ");
	Serial.print(ai.ain1);
	Serial.print(" - ");
	Serial.print(ai.ain2);
	Serial.print(" - ");
	Serial.println(ai.ain3);

if you want read a single analog input or channel:

	int ana = pcf8591.analogRead(AIN0); // read analog 0

This IC have multiple type of read and you can use Analog input or analog channel (when you use single read analog input and channel are the same:

For example to read the value of channel 0 in Two differential input you must do:

	int ana = pcf8591.analogRead(CHANNEL0, TWO_DIFFERENTIAL_INPUT); // read analog 0

If you want write an analog value you must do (the value is from 0 to 255):

	pcf8591.analogWrite(128);

Additional feature is to read a write voltage: For the calculation of voltage you must pass some parameter:

• microcontrollerReferenceVoltage: get voltage from microcontroller voltage (only AVR no esp8266 for esp 3.3v fixed)
• referenceVoltage: if microcontrollerReferenceVoltage false take this value

The command are:

	void voltageWrite(float value, bool microcontrollerReferenceVoltage = true, float referenceVoltage = 5.0);
	float voltageRead(uint8_t analogPin, bool microcontrollerReferenceVoltage = true, float referenceVoltage = 5.0);

An examples is:

	pcf8591.voltageWrite(2.7); // 2.7Volts output
	delay(3000);

	float ana0V = pcf8591.voltageRead(AIN0); // Read voltage from analog 0
	Serial.println(ana0V);

For the examples I use this wire schema on breadboard: