X9C Series Digital Potentiometer - Arduino Library

About

Main use case: Variable Reference Resistor for Adjustable Voltage Divider Networks Description
The X9C10C is a digitally controlled potentiometer (digipot) from the X9C series, providing 1 / 10 / 50 / 100 kΩ resistance with 100 tap points (0-99) and ±20% resistance tolerance, that can be adjusted via digital signals.
Operated between -5 to 5V logic levels, it features a non-volatile memory with (typical) 1e5 write cycles to store wiper positions. The device uses a 3-wire interface (CS, U/D', INC) for increment/decrement control, with 1µs typical step response time, making it ideal for applications requiring programmable resistance like gain adjustment, calibration, or volume control.

This repository aims to accurately replicate timing characteristics and resistance taper behaviour of this series of digital potentiometers.

Pinout diagram
IMPORTANT: All digital pots in internet examples use the same device to divide the voltage. But I use external resistive devices (strain gauges, soft resistive sensors, etc.) in my research work, and require a variable reference resistor for adjustable voltage divider networks. Hence, this ckt diagram helps in using it as a variable reference resistor. https://github.com/tingerlingerr/DigiPotX9C/blob/main/wiring/

Advantages

• Dirt cheap (like most chinese products)
• Unlike mechanical potentiometers, no physical wear; offers repeatable digital control
• Retains last wiper position after power loss (for up to 100 years).
• Compact size; max 16mW (10mW for X9C102) power consumption.
• Suitable for applications requiring auto-calibration of resistive-based sensing / actuating devices, removing undesired manual intervention.

Disadvantages

• Modules have shown to be unreliable at times
• ±20% high tolerance a detrimental factor in critical systems; can be mitigated via software to some extent.
• Limited to ~3mA current; ±1 LSB wiper position uncertainty.
• Some have complained that full rresistance often reached in 30–50 steps, not 100.

Limitations

• Always 100 steps resolution, irrespective of module; resolution of 100kΩ module only 1kΩ, not be very precise.
• Datasheet mentions ONLY minimum timing specs - what if real dalay is more? How much more? This is cheap electronics. We may never know!!

Reason for building library

• Refer IMPORTANT note in Pinout diagram
• Verifies whether correct GPIO pin is connected (for ESP32 only).
• Considers the fact a user may want to increase wiper position by more than 1 position a time.
• Minimally written library balancing speed of operation, and reliability & ease of use.
• (Frankly) Self-learning
  

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📋 Folder Structure

DigiPotX9C/
├── docs/
├── examples/
├── src/
├── wiring/
├ Changelog
├ LICENSE
├ Readme
├ datasheet
├ keywords
└ library.properties

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To do

Have a "getResistanceFeedback()" function that reads the actual resistance, instead of mathematical calculation based on wiper position. But need to test that on field.

Credit

1. Renesas X9C102, X9C103, X9C104, X9C503 Digitally Controlled Potentiometer (XDCP™) Datasheet (https://www.renesas.com/en/document/dst/x9c102-x9c103-x9c104-x9c503-datasheet?r=502676)

2. Inspirations:

   • https://github.com/RobTillaart/X9C10X
   • https://github.com/GitMoDu/FastX9CXXX

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