Output - MCP42xxx Digipot¶

MCP42xxx/MCP41xxx Digital potentiometers

Plugin details¶

Type: Output

Name: MCP42xxx Digipot

Status: COLLECTION G

GitHub: P162_MCP42xxx.ino

Maintainer: tonhuisman

Used libraries: SPI

Description¶

The MCP42xxx/MCP41xxx (the xxx specifies the max resistance value) are dual/single digital potentiometers (digipot), that can be controlled via SPI, and offer a 256 step resolution.

NB: The daisy-chain feature, available in the MCP42xxx chips, is not implemented in this plugin.

Hardware¶

This plugin is built and tested using a DFRobot DFR0520 Dual Digipot board where also a suggestion for wiring up the board is shown.

The board will tolerate 5V power and signals, but when powering the board at 5V and connecting to an ESP, the signal levels must be adjusted to 3.3V by using a level converter, to avoid damaging the ESP!

Configuration¶

Name: Required by ESPEasy, must be unique among the list of available devices/tasks.
Enabled: The device can be disabled or enabled. When not enabled the device should not use any resources.

Sensor¶

GPIO -> CS PIN: Configuring the CS (Chip select) pin is required to correctly address the board, and start the plugin. Also, the standard SPI interface pins MOSI and CLK have to be configured and connected.
GPIO -> RST PIN (optional): Not all boards have the RST (Reset) pin of the chip available. When not available or not used, it should be set to - None -. This pin is not available on the MCP41xxx chips.
GPIO -> SHDN PIN (optional): Not all boards have the SHDN (Shutdown) pin of the chip available. When not available or not used, it should be set to - None - (Shutdown is explained below). This pin is not available on the MCP41xxx chips.

Device Settings¶

Initial value Wx: Range: 0..255. Set the value of the wiper (W) after initialization. By default it is set at the center of the range, 128, corresponding to the value after power-on or reset. Lower values bring the wiper closer to PBx, and higher values closer to PAx level.
Initial shutdown Wx: The wiper can be initially set to Shutdown mode, where the PAx connection is disconnected, and Wx is connected to PBx. When both outputs are initially set to Shutdown, and the SHDN pin is configured, that pin will be used to shutdown the chip. Shutdown mode is undone by setting a value to one of the outputs, using the command described below.

These settings are available for both W0 and W1. NB: The W1 settings can’t be applied on the MCP41xxx chips, as that has only 1 digipot.

Value at Shutdown: Range -1..256. Value for the output variables when Shutdown mode for that output is set.
Send values on change: When checked, and Interval set to 0, events will only be generated, and sent to any configured Controllers, when a Value is changed. On startup, the initial values will be sent out, but that’s the default behavior for ESPEasy.

Data Acquisition¶

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

Interval By default, Interval will not be set. The values will be optionally sent to any configured controllers using the interval, when set.

Values¶

The plugin provides the W0 and W1 values. A formula can be set to recalculate. The number of decimals can be set as desired, and defaults to 0, as these can only be set to integer values, but a formula could result in decimal values.

In selected builds, per Value is a Stats checkbox available, that when checked, gathers the data and presents recent data in a graph, as described here: Task Value Statistics:

Commands available¶

Command Syntax	Extra information
`digipot,reset`	Sending this command to the task the digipot will be reset to the default wiper settings (128). When a `RST` pin is configured, that will be shortly pulled to GND to reset the hardware, else the initial settings will be set to the chip. On reset, the Initial Shutdown settings will not be applied!
`digipot,shutdown[,<wiper>]` `<wiper>`: Optional wiper to shutdown. `0` = W0 `1` = W1 `2` = Both wipers (default when ommitted)	This command will set the indicated wiper to Shutdown mode. When no wiper is given, then both wipers will be set to shutdown mode, optionally using the hardware `SHDN` pin if that’s configured. Shutdown mode will be released when a value is set to a wiper.
`digipot,<wiper>,<value>` `<wiper>`: Wiper to set the value for. `0` = W0 `1` = W1 `2` = Both wipers `<value>`: Range 0..255 to set the wiper to.	This command will set the provided value to the indicated wiper. When using wiper 2 (both), then a single command will change both values at the same moment. When setting a value to a wiper, it will also release the shutdown mode, when enabled.

Command Syntax

Extra information

digipot,reset

Sending this command to the task the digipot will be reset to the default wiper settings (128). When a RST pin is configured, that will be shortly pulled to GND to reset the hardware, else the initial settings will be set to the chip.

On reset, the Initial Shutdown settings will not be applied!

digipot,shutdown[,<wiper>]

<wiper>: Optional wiper to shutdown.

0 = W0

1 = W1

2 = Both wipers (default when ommitted)

This command will set the indicated wiper to Shutdown mode. When no wiper is given, then both wipers will be set to shutdown mode, optionally using the hardware SHDN pin if that’s configured.

Shutdown mode will be released when a value is set to a wiper.

digipot,<wiper>,<value>

<wiper>: Wiper to set the value for.

0 = W0

1 = W1

2 = Both wipers

<value>: Range 0..255 to set the wiper to.

This command will set the provided value to the indicated wiper. When using wiper 2 (both), then a single command will change both values at the same moment.

When setting a value to a wiper, it will also release the shutdown mode, when enabled.

Change log¶

Changed in version 2.0: …

added 2024-04-15 Initial release version.