Analog input - PCF8591


Plugin details

Type: Analog input

Name: PCF8591

Status: NORMAL

GitHub: P007_PCF8591.ino

Maintainer: .

Used libraries: .


The PCF8591 is an Analog to Digital converter, connected via an I2C bus. The plugin supports to read from 1 up to 4 input values. If desired, multiple Tasks can be defined, addressing other, or duplicate, inputs.

Supported hardware

../_images/P007_PCF8591Module.jpg ../_images/P007_PCF8591.jpg

The chip is separately available, or on a complete module, and can be bought from several sources.

it is compatible with 3.3V logic, when powered with 3.3V, so no level converters are needed to connect it to an ESP.



  • Name A unique name should be entered here.

  • Enabled The device can be disabled or enabled. When not enabled the device should not use any resources.

I2C Options

The available settings here depend on the build used. At least the Force Slow I2C speed option is available, but selections for the I2C Multiplexer can also be shown. For details see the Hardware page

  • I2C Address: The address the device is using. There are a number of addresses the module can use, and they can usually be set at the board using jumper pins.

The available options:

  • Port As there are multiple Ports available on each board, the desired Port can be selected here.

Available options:

  • Force Slow I2C Speed Should be enabled, as by PCF8591 chip specification, the I2C bus clock should be max. 100 kHz. This is the default Slow device Clock Speed I2C setting for ESPEasy (see Hardware tab). When using the default I2C Clock Speed of 400 kHz, readings will be unreliable, especially when reading multiple values in 1 task.

Output Configuration

  • Number Output Values As this device supports 4 Analog inputs, the number of measurements handled by this task can be configured.

Available options:


The names should speak for themselves.

When selecting f.e. the Quad option and saving the settings, the number of output values is changed to 4, resulting in these Values:



If Port is set to A1, A2 or A3, then the value measured from the selected Port will be stored in the first Values field, and any next field(s) consecutively. If Number Output Values is larger than the remaining number of Ports, then the remaining Values will be set to 0!

For any ‘excess’ values, events will be generated!

Data Acquisition

This group of settings, Single event with all values, Send to Controller and Interval settings are standard available configuration items. Send to Controller is only visible when one or more Controllers are configured.

  • Interval By default, Interval will be set to 60 sec. It is the frequency used to read sensor values and send these to any Controllers configured for this device.


The name for the value(s) is initially set to a default name, but can be changed if desired. Also, a formula can be entered to re-calculate a value before display/sending to a controller, and the number of decimals can be changed, for a Temperature, usually 1 decimal is enough to be displayed (value will be rounded).

Change log

Changed in version 2.0:

added 2021-08-06 Selection of 1 to 4 input values to be read.

added 2021-08-03 Replaced single Port inputfield with separate I2CAddress and Port selections.

added Major overhaul for 2.0 release.

New in version 1.0:

added Initial release version.