diff --git a/libraries/MCP4261/.arduino-ci.yml b/libraries/MCP4261/.arduino-ci.yml
new file mode 100644
index 00000000..a7a93bac
--- /dev/null
+++ b/libraries/MCP4261/.arduino-ci.yml
@@ -0,0 +1,32 @@
+platforms:
+  rpipico:
+    board: rp2040:rp2040:rpipico
+    package: rp2040:rp2040               #  name:architecture:board
+    gcc:
+      features:
+      defines:
+        - ARDUINO_ARCH_RP2040
+      warnings:
+      flags:
+
+
+packages:
+  rp2040:rp2040:
+    url: https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json
+  teensy:Teensy:
+    url: https://www.pjrc.com/teensy/package_teensy_index.json
+
+
+compile:
+  # Choosing to run compilation tests on 2 different Arduino platforms
+  platforms:
+    - uno
+    # - due
+    # - zero
+    # - leonardo
+    - m4
+    - esp32
+    - esp8266
+    # - mega2560
+    - rpipico
+
diff --git a/libraries/MCP4261/.github/FUNDING.yml b/libraries/MCP4261/.github/FUNDING.yml
new file mode 100644
index 00000000..554358c3
--- /dev/null
+++ b/libraries/MCP4261/.github/FUNDING.yml
@@ -0,0 +1,4 @@
+# These are supported funding model platforms
+
+github: RobTillaart
+custom: "https://www.paypal.me/robtillaart"
diff --git a/libraries/MCP4261/.github/workflows/arduino-lint.yml b/libraries/MCP4261/.github/workflows/arduino-lint.yml
new file mode 100644
index 00000000..7f8f4ef4
--- /dev/null
+++ b/libraries/MCP4261/.github/workflows/arduino-lint.yml
@@ -0,0 +1,13 @@
+name: Arduino-lint
+
+on: [push, pull_request]
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@v4
+      - uses: arduino/arduino-lint-action@v1
+        with:
+          library-manager: update
+          compliance: strict
\ No newline at end of file
diff --git a/libraries/MCP4261/.github/workflows/arduino_test_runner.yml b/libraries/MCP4261/.github/workflows/arduino_test_runner.yml
new file mode 100644
index 00000000..dbd0ce79
--- /dev/null
+++ b/libraries/MCP4261/.github/workflows/arduino_test_runner.yml
@@ -0,0 +1,17 @@
+name: Arduino CI
+
+on: [push, pull_request]
+
+jobs:
+  runTest:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 2.6
+      - run: |
+          gem install arduino_ci
+          arduino_ci.rb
diff --git a/libraries/MCP4261/.github/workflows/jsoncheck.yml b/libraries/MCP4261/.github/workflows/jsoncheck.yml
new file mode 100644
index 00000000..1cbb5e2c
--- /dev/null
+++ b/libraries/MCP4261/.github/workflows/jsoncheck.yml
@@ -0,0 +1,18 @@
+name: JSON check
+
+on:
+  push:
+    paths:
+      - '**.json'
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@v4
+      - name: json-syntax-check
+        uses: limitusus/json-syntax-check@v2
+        with:
+          pattern: "\\.json$"
\ No newline at end of file
diff --git a/libraries/MCP4261/CHANGELOG.md b/libraries/MCP4261/CHANGELOG.md
new file mode 100644
index 00000000..4f96407a
--- /dev/null
+++ b/libraries/MCP4261/CHANGELOG.md
@@ -0,0 +1,10 @@
+# Change Log MCP4261
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](http://keepachangelog.com/)
+and this project adheres to [Semantic Versioning](http://semver.org/).
+
+
+## [0.1.0] - 2024-02-21
+- initial version
diff --git a/libraries/MCP4261/LICENSE b/libraries/MCP4261/LICENSE
new file mode 100644
index 00000000..37fe70e5
--- /dev/null
+++ b/libraries/MCP4261/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2024-2024 Rob Tillaart
+
+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.
diff --git a/libraries/MCP4261/MCP4261.cpp b/libraries/MCP4261/MCP4261.cpp
new file mode 100644
index 00000000..1da20392
--- /dev/null
+++ b/libraries/MCP4261/MCP4261.cpp
@@ -0,0 +1,386 @@
+//
+//    FILE: MCP4261.cpp
+//  AUTHOR: Rob Tillaart
+// VERSION: 0.1.0
+//    DATE: 2024-02-21
+// PURPOSE: Arduino library for MCP4261 SPI based digital potentiometers.
+//     URL: https://github.com/RobTillaart/MCP4261
+
+
+#include "MCP4261.h"
+
+
+//  see page 18 datasheet
+#define MCP4261_IGNORE_CMD        0x00
+#define MCP4261_WRITE_CMD         0x00
+#define MCP4261_SHUTDOWN_CMD      0x20
+#define MCP4261_NONE_CMD          0x30
+
+
+  //       HARDWARE SPI
+MCP4261::MCP4261(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+{
+  _pmCount  = 2;
+  _maxValue = 255;
+  _select   = select;
+  _shutdown = shutdown;
+  _dataIn   = 255;
+  _dataOut  = 255;
+  _clock    = 255;
+  _hwSPI    = true;
+  _mySPI    = mySPI;
+  _spi_settings = SPISettings(_SPIspeed, MSBFIRST, SPI_MODE0);
+}
+
+
+//       SOFTWARE SPI
+MCP4261::MCP4261(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+{
+  _pmCount  = 2;
+  _maxValue = 255;
+  _select   = select;
+  _shutdown = shutdown;
+  _dataIn   = dataIn;
+  _dataOut  = dataOut;
+  _clock    = clock;
+  _hwSPI    = false;
+  _mySPI    = NULL;
+}
+
+
+void MCP4261::begin(uint16_t value)
+{
+  pinMode(_select, OUTPUT);
+  digitalWrite(_select, HIGH);
+  pinMode(_shutdown, OUTPUT);
+  digitalWrite(_shutdown, HIGH);
+
+  setSPIspeed(1000000);
+
+  if(_hwSPI)
+  {
+    //  _mySPI->end();
+    //  _mySPI->begin();
+    //  delay(1);
+  }
+  else
+  {
+    pinMode(_dataIn, INPUT);
+    pinMode(_dataOut, OUTPUT);
+    pinMode(_clock,   OUTPUT);
+    digitalWrite(_dataOut, LOW);
+    digitalWrite(_clock,   LOW);
+  }
+  reset(value);
+}
+
+
+void MCP4261::reset(uint16_t value)
+{
+  digitalWrite(_shutdown, LOW);
+  digitalWrite(_shutdown, HIGH);
+  setValue(value);  //  set all to same value.
+}
+
+
+
+/////////////////////////////////////////////////////////////////////////////
+//
+//  SET VOLATILE VALUE
+//
+bool MCP4261::setValue(uint16_t value)
+{
+  setValue(0, value);
+  setValue(1, value);
+  return true;
+}
+
+
+bool MCP4261::setValue(uint8_t pm, uint16_t value)
+{
+  if (pm >= _pmCount) return false;
+  if (value > _maxValue) return false;
+  _value[pm] = value;
+
+  uint8_t cmd = 0x00;
+  if (pm == 1) cmd = 0x10;
+  if (value > 0xFF) cmd |= (value >> 8);  //  high bits
+  writeDevice(2, cmd, value & 0xFF);
+  return true;
+}
+
+
+uint16_t MCP4261::getValue(uint8_t pm)
+{
+  if (pm >= _pmCount) return 0;
+  return _value[pm];
+}
+
+
+bool MCP4261::incrValue(uint8_t pm)
+{
+  if (pm >= _pmCount) return false;
+  if (_value[pm] >= _maxValue) return false;
+  _value[pm]++;
+
+  uint8_t cmd = 0x04;
+  if (pm == 1) cmd = 0x14;
+  writeDevice(1, cmd, cmd);  //  value2 = DUMMY
+  return true;
+}
+
+
+bool MCP4261::decrValue(uint8_t pm)
+{
+  if (pm >= _pmCount) return false;
+  if (_value[pm] == 0) return false;
+  _value[pm]--;
+
+  uint8_t cmd = 0x08;
+  if (pm == 1) cmd = 0x18;
+  writeDevice(1, cmd, cmd);  //  value2 = DUMMY
+  return true;
+}
+
+
+
+/////////////////////////////////////////////////////////////////////////////
+//
+//  SET NON-VOLATILE VALUE
+//
+bool MCP4261::setValueNV(uint8_t pm, uint16_t value)
+{
+  if (pm >= _pmCount) return false;
+  if (value > _maxValue) return false;
+
+  uint8_t cmd = 0x20;
+  if (pm == 1) cmd = 0x30;
+  if (value > 0xFF) cmd |= (value >> 8);  //  high bits
+  writeDevice(2, cmd, value & 0xFF);
+  return true;
+}
+
+
+/////////////////////////////////////////////////////////////////////////////
+//
+//  MISC
+//
+uint8_t MCP4261::pmCount()
+{
+  return _pmCount;
+}
+
+
+void MCP4261::powerOn()
+{
+  digitalWrite(_shutdown, HIGH);
+}
+
+
+void MCP4261::powerOff()
+{
+  digitalWrite(_shutdown, LOW);
+}
+
+
+bool MCP4261::isPowerOn()
+{
+  return digitalRead(_shutdown) == HIGH;
+}
+
+
+/////////////////////////////////////////////////////////////////////////////
+//
+//  SPI
+//
+void MCP4261::setSPIspeed(uint32_t speed)
+{
+  _SPIspeed = speed;
+  _spi_settings = SPISettings(_SPIspeed, MSBFIRST, SPI_MODE0);
+}
+
+
+uint32_t MCP4261::getSPIspeed()
+{
+  return _SPIspeed;
+}
+
+
+bool MCP4261::usesHWSPI()
+{
+  return _hwSPI;
+}
+
+
+/////////////////////////////////////////////////////////////////////////////
+//
+//  PROTECTED
+//
+
+/*
+TODO - see page 46
+- need read8, read16
+- bid8, bidi16
+*/
+
+
+//
+//  USES SPI MODE 0
+//
+void MCP4261::writeDevice(uint8_t count, uint8_t value1, uint8_t value2)
+{
+  digitalWrite(_select, LOW);
+  if (_hwSPI)
+  {
+    _mySPI->beginTransaction(_spi_settings);
+    _mySPI->transfer(value1);
+    if (count == 2) _mySPI->transfer(value2);
+    _mySPI->endTransaction();
+  }
+  else      //  Software SPI
+  {
+    swSPI_write(value1);
+    if (count == 2) swSPI_write(value2);
+  }
+  digitalWrite(_select, HIGH);
+}
+
+
+//  MSBFIRST
+void MCP4261::swSPI_write(uint8_t value)
+{
+  uint8_t clk = _clock;
+  uint8_t dao = _dataOut;
+  
+  //  MSBFIRST
+  for (uint8_t mask = 0x80; mask; mask >>= 1)
+  {
+    digitalWrite(dao,(value & mask));
+    digitalWrite(clk, HIGH);
+    digitalWrite(clk, LOW);
+  }
+}
+
+
+
+////////////////////////////////////////////////////////////////////////////
+//
+//  DERIVED CLASSES MCP41xx SERIES
+//
+MCP4141::MCP4141(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+        :MCP4261(select, shutdown, mySPI)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+MCP4141::MCP4141(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+        :MCP4261(select, shutdown, dataIn, dataOut, clock)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+//
+
+MCP4142::MCP4142(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+        :MCP4261(select, shutdown, mySPI)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+MCP4142::MCP4142(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+        :MCP4261(select, shutdown, dataIn, dataOut, clock)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+//
+
+MCP4161::MCP4161(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+        :MCP4261(select, shutdown, mySPI)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+MCP4161::MCP4161(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+        :MCP4261(select, shutdown, dataIn, dataOut, clock)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+//
+
+MCP4162::MCP4162(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+        :MCP4261(select, shutdown, mySPI)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+MCP4162::MCP4162(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+        :MCP4261(select, shutdown, dataIn, dataOut, clock)
+{
+  _pmCount  = 1;
+  _maxValue = MCP41XX_MAX_VALUE;
+}
+
+
+////////////////////////////////////////////////////////////////////////////
+//
+//  DERIVED CLASSES MCP42xx SERIES
+//
+MCP4241::MCP4241(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+        :MCP4261(select, shutdown, mySPI)
+{
+  _pmCount  = 2;
+  _maxValue = MCP42XX_MAX_VALUE;
+}
+
+MCP4241::MCP4241(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+        :MCP4261(select, shutdown, dataIn, dataOut, clock)
+{
+  _pmCount  = 2;
+  _maxValue = MCP42XX_MAX_VALUE;
+}
+
+//
+
+MCP4242::MCP4242(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+        :MCP4261(select, shutdown, mySPI)
+{
+  _pmCount  = 2;
+  _maxValue = MCP42XX_MAX_VALUE;
+}
+
+MCP4242::MCP4242(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+        :MCP4261(select, shutdown, dataIn, dataOut, clock)
+{
+  _pmCount  = 2;
+  _maxValue = MCP42XX_MAX_VALUE;
+}
+
+//
+
+MCP4262::MCP4262(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI)
+        :MCP4261(select, shutdown, mySPI)
+{
+  _pmCount  = 2;
+  _maxValue = MCP42XX_MAX_VALUE;
+}
+
+MCP4262::MCP4262(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)
+        :MCP4261(select, shutdown, dataIn, dataOut, clock)
+{
+  _pmCount = 2;
+  _maxValue = MCP42XX_MAX_VALUE;
+}
+
+
+
+//  -- END OF FILE --
+
diff --git a/libraries/MCP4261/MCP4261.h b/libraries/MCP4261/MCP4261.h
new file mode 100644
index 00000000..75b94642
--- /dev/null
+++ b/libraries/MCP4261/MCP4261.h
@@ -0,0 +1,174 @@
+#pragma once
+//
+//    FILE: MCP4261.h
+//  AUTHOR: Rob Tillaart
+// VERSION: 0.1.0
+//    DATE: 2024-02-21
+// PURPOSE: Arduino library for MCP4261 SPI based digital potentiometers.
+//     URL: https://github.com/RobTillaart/MCP4261
+
+
+#include "Arduino.h"
+#include "SPI.h"
+
+
+#define MCP4261_LIB_VERSION           (F("0.1.0"))
+
+
+#ifndef MCP41XX_MIDDLE_VALUE
+#define MCP41XX_MIDDLE_VALUE          64
+#endif
+
+#ifndef MCP41XX_MAX_VALUE
+#define MCP41XX_MAX_VALUE             129
+#endif
+
+
+#ifndef MCP42XX_MIDDLE_VALUE
+#define MCP42XX_MIDDLE_VALUE          129
+#endif
+
+#ifndef MCP42XX_MAX_VALUE
+#define MCP42XX_MAX_VALUE             257
+#endif
+
+
+#ifndef __SPI_CLASS__
+  //  MBED must be tested before RP2040
+  #if defined(ARDUINO_ARCH_MBED)
+  #define __SPI_CLASS__   SPIClass
+  #elif defined(ARDUINO_ARCH_RP2040)
+  #define __SPI_CLASS__   SPIClassRP2040
+  #else
+  #define __SPI_CLASS__   SPIClass
+  #endif
+#endif
+
+
+class MCP4261
+{
+public:
+  //       HARDWARE SPI
+  MCP4261(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  //       SOFTWARE SPI
+  MCP4261(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+
+  void     begin(uint16_t value);
+  void     reset(uint16_t value);
+  uint8_t  pmCount();
+
+
+  //       set both potmeters (just a wrapper)
+  bool     setValue(uint16_t value);
+  //       set single potmeter (0 or 1)
+  bool     setValue(uint8_t pm, uint16_t value);
+  uint16_t getValue(uint8_t pm = 0);
+
+  bool     incrValue(uint8_t pm);
+  bool     decrValue(uint8_t pm);
+
+  //       Set non volatile potmeter
+  //       not tested
+  bool     setValueNV(uint8_t pm, uint16_t value);
+
+  //       speed in Hz
+  void     setSPIspeed(uint32_t speed);
+  uint32_t getSPIspeed();
+  bool     usesHWSPI();  //  debugging
+
+
+  //       MISC
+  void     powerOn();
+  void     powerOff();
+  bool     isPowerOn();
+
+
+protected:
+  uint8_t  _dataIn;
+  uint8_t  _dataOut;
+  uint8_t  _clock;
+  uint8_t  _select;
+  uint8_t  _shutdown;
+  bool     _hwSPI;
+  uint32_t _SPIspeed;
+
+  uint16_t _value[2] = { 0, 0 };
+  uint8_t  _pmCount;
+  uint16_t _maxValue;
+
+  void     writeDevice(uint8_t count, uint8_t value1, uint8_t value2);
+  void     swSPI_write(uint8_t value);
+
+  __SPI_CLASS__ * _mySPI;
+  SPISettings   _spi_settings;
+};
+
+
+
+////////////////////////////////////////////////////
+//
+//  DERIVED CLASSES MCP41xx SERIES
+//
+class MCP4141 : public MCP4261
+{
+public:
+  MCP4141(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  MCP4141(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+};
+
+
+class MCP4142 : public MCP4261
+{
+public:
+  MCP4142(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  MCP4142(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+};
+
+
+class MCP4161 : public MCP4261
+{
+public:
+  MCP4161(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  MCP4161(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+};
+
+
+class MCP4162 : public MCP4261
+{
+public:
+  MCP4162(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  MCP4162(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+};
+
+
+/////////////////////////////////////////////////////////////////////////////
+//
+//  DERIVED CLASSES MCP42xx SERIES
+//
+class MCP4241 : public MCP4261
+{
+public:
+  MCP4241(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  MCP4241(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+};
+
+
+class MCP4242 : public MCP4261
+{
+public:
+  MCP4242(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  MCP4242(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+};
+
+
+class MCP4262 : public MCP4261
+{
+public:
+  MCP4262(uint8_t select, uint8_t shutdown, __SPI_CLASS__ * mySPI = &SPI);
+  MCP4262(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock);
+};
+
+
+
+//  -- END OF FILE --
+
diff --git a/libraries/MCP4261/README.md b/libraries/MCP4261/README.md
new file mode 100644
index 00000000..7d4ca383
--- /dev/null
+++ b/libraries/MCP4261/README.md
@@ -0,0 +1,208 @@
+
+[![Arduino CI](https://github.com/RobTillaart/MCP4261/workflows/Arduino%20CI/badge.svg)](https://github.com/marketplace/actions/arduino_ci)
+[![Arduino-lint](https://github.com/RobTillaart/MCP4261/actions/workflows/arduino-lint.yml/badge.svg)](https://github.com/RobTillaart/MCP4261/actions/workflows/arduino-lint.yml)
+[![JSON check](https://github.com/RobTillaart/MCP4261/actions/workflows/jsoncheck.yml/badge.svg)](https://github.com/RobTillaart/MCP4261/actions/workflows/jsoncheck.yml)
+[![GitHub issues](https://img.shields.io/github/issues/RobTillaart/MCP4261.svg)](https://github.com/RobTillaart/MCP4261/issues)
+
+[![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/RobTillaart/MCP4261/blob/master/LICENSE)
+[![GitHub release](https://img.shields.io/github/release/RobTillaart/MCP4261.svg?maxAge=3600)](https://github.com/RobTillaart/MCP4261/releases)
+[![PlatformIO Registry](https://badges.registry.platformio.org/packages/robtillaart/library/MCP4261.svg)](https://registry.platformio.org/libraries/robtillaart/MCP4261)
+
+[![Commits since latest](https://img.shields.io/github/commits-since/RobTillaart/MCP4261/latest)](https://github.com/RobTillaart/MCP4261/commits/master)
+
+
+# MCP4261
+
+Arduino library for MCP4261 SPI based digital potentiometers and compatibles.
+
+
+## Description
+
+**Experimental**
+
+The MCP4261 library supports both hardware SPI and software SPI up to 10 MHz.
+
+These series of potmeters (rheostats) come in values of 5, 10, 50 and 100 kΩ (±20%).
+
+Where other potmeters uses a range of 0..127 or 0.255, these series potmeters
+use a range 0..129 and 0..257. This implies some extra care to set the wiper
+to end position.
+
+The library supports setting the value of the potmeters and caches this setting.
+This way it can be retrieved very fast.
+
+Furthermore the library has two functions to increase and decrease
+the value of a potmeter.
+
+
+Feedback, issues and improvements are welcome, 
+Please open an issue on GitHub.
+
+
+### Not implemented yet
+
+The library is under development and not all functionality is implemented.
+(as I only needed to set values).
+
+- EEPROM, 10 addresses of 10 bits. (MCP4261 et al )
+- Non volatile registers for power on setup.. (partially)
+- read back from device
+- read status
+- TCON register
+- High Voltage something?
+
+
+### Compatibles
+
+These are the devices that should work with this library.
+Only the 4261 is tested.
+
+|  Number  |  Type    |  pots  |   POR    |  MaxValue  |  Notes  |
+|:--------:|:--------:|:------:|:--------:|:----------:|:--------|
+| MCP4141  | Potmeter |   1    | NV-Wiper |    129     |
+| MCP4142  | Rheostat |   1    | NV-Wiper |    129     |
+| MCP4161  | Potmeter |   1    | NV-Wiper |    257     |
+| MCP4162  | Rheostat |   1    | NV-Wiper |    257     |
+| MCP4241  | Potmeter |   2    | NV-Wiper |    129     |
+| MCP4242  | Rheostat |   2    | NV-Wiper |    129     |
+| MCP4261  | Potmeter |   2    | NV-Wiper |    257     |  base class
+| MCP4262  | Rheostat |   2    | NV-Wiper |    257     |
+
+To investigate:
+
+MCP4131/32/51/52, MCP4231/32/51/52, these have no NV RAM so they 
+have a POR power on reset of  middle value (= half max value.
+
+
+MCP4151 Reichelt  
+MCP4262 Mouser
+
+
+### Related
+
+TODO: list of other digital pot meters / rheostats.
+
+
+#### Related
+
+
+
+|  Address  |  Function                |  Memory Type  |
+|:---------:|:------------------------:|:--------------|
+|  00h      |  Volatile Wiper 0        |  RAM          |
+|  01h      |  Volatile Wiper 1        |  RAM          |
+|  02h      |  Non-Volatile Wiper 0    |  EEPROM       |
+|  03h      |  Non-Volatile Wiper 1    |  EEPROM       |
+|  04h      |  Volatile TCON Register  |  RAM          |
+|  05h      |  Status Register         |  RAM          |
+|  06h      |  Data EEPROM             |  EEPROM       |
+|  07h      |  Data EEPROM             |  EEPROM       |
+|  08h      |  Data EEPROM             |  EEPROM       |
+|  09h      |  Data EEPROM             |  EEPROM       |
+|  0Ah      |  Data EEPROM             |  EEPROM       |
+|  0Bh      |  Data EEPROM             |  EEPROM       |
+|  0Ch      |  Data EEPROM             |  EEPROM       |
+|  0Dh      |  Data EEPROM             |  EEPROM       |
+|  0Eh      |  Data EEPROM             |  EEPROM       |
+|  0Fh      |  Data EEPROM             |  EEPROM       |
+
+
+## Interface
+
+```cpp
+#include "MCP4261.h"
+```
+
+
+### Constructor
+
+- **MCP4261(uint8_t select, uint8_t shutdown, \__SPI_CLASS__ \* mySPI = &SPI)**
+HW SPI constructor.
+- **MCP4261(uint8_t select, uint8_t shutdown, uint8_t dataIn, uint8_t dataOut, uint8_t clock)**
+SW SPI Constructor. The dataIn pin is not used yet.
+- **void begin(uint8_t value)** user must explicit set initial value.
+- **void reset(uint8_t value)** user must explicit set initial value.
+- **uint8_t pmCount()** returns 1 or 2, depending on device type.
+
+
+### Set Volatile Values
+
+- **bool setValue(uint8_t value)** set all potmeters to the same value. (wrapper).
+Returns true.
+- **bool setValue(uint8_t pm, uint8_t value)** set single potmeter (0 or 1).
+Returns false if pm > pmCount.
+- **uint8_t getValue(uint8_t pm = 0)** returns value from cache.
+- **bool incrValue(uint8_t pm)**
+- **bool decrValue(uint8_t pm)**
+
+
+### Set Volatile Values
+
+**Experimental**
+
+TODO: how does this fit in interface as reset() always sets a value.
+
+- **bool setValueNV(uint8_t pm, uint16_t value)**
+
+
+### EEPROM
+
+Not implemented yet
+
+### SPI
+
+Note changing the SPI speed might affect other devices on the same SPI bus.
+So use with care.
+
+- **void setSPIspeed(uint32_t speed)** default 1MHz, typical 4 MHz.
+- **uint32_t getSPIspeed()** idem.
+- **bool usesHWSPI()** idem.
+
+
+### Power
+
+- **void powerOn()** idem.
+- **void powerOff()** idem.
+- **bool isPowerOn()** idem.
+
+
+## Future
+
+#### Must
+
+- improve documentation
+
+#### Should 
+
+- read registers.
+  - read values.
+  - status register
+  - TCON
+
+#### Could
+
+- EEPROM support
+  - 10 registers, 10 bit
+  - bool writeEEPROM(address, uint16_t value);
+  - uint16_t readEEPROM(address);
+- write to non-volatile register 02/03 to set Power On Reset values
+  - read when reset?
+  - how to fit in use model.
+- unit tests
+- examples
+- error handling
+  - improve return values
+- investigate performance 
+  - AVR SW SPI?
+
+#### Won't
+
+
+## Support
+
+If you appreciate my libraries, you can support the development and maintenance.
+Improve the quality of the libraries by providing issues and Pull Requests, or
+donate through PayPal or GitHub sponsors.
+
+Thank you,
+
diff --git a/libraries/MCP4261/documents/MCP4151_MIC.pdf b/libraries/MCP4261/documents/MCP4151_MIC.pdf
new file mode 100644
index 00000000..5e62288f
Binary files /dev/null and b/libraries/MCP4261/documents/MCP4151_MIC.pdf differ
diff --git a/libraries/MCP4261/documents/MCP4261.pdf b/libraries/MCP4261/documents/MCP4261.pdf
new file mode 100644
index 00000000..3b28ecdd
Binary files /dev/null and b/libraries/MCP4261/documents/MCP4261.pdf differ
diff --git a/libraries/MCP4261/examples/MCP4261_demo/MCP4261_demo.ino b/libraries/MCP4261/examples/MCP4261_demo/MCP4261_demo.ino
new file mode 100644
index 00000000..f6faf4f7
--- /dev/null
+++ b/libraries/MCP4261/examples/MCP4261_demo/MCP4261_demo.ino
@@ -0,0 +1,147 @@
+//
+//    FILE: MCP4261_demo.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo
+//     URL: https://github.com/RobTillaart/MCP4261
+
+
+#include "MCP4261.h"
+
+
+uint32_t start, stop;
+
+
+//  select, shutdown, dataIn, dataOut, clock == SOFTWARE SPI
+// MCP4261 pot(10, 6, 7, 8, 9);
+
+//  select, shutdown, &SPI === HW SPI UNO clock = 13, dataOut = 11
+MCP4261 pot(10, 6, &SPI);
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+
+  SPI.begin();
+
+  pot.begin(0);  //  initial value
+
+  //  test_extremes();
+  //test_sinus();
+  test_sawtooth();
+  test_incr_decr();
+  //test_timing();
+
+  Serial.println("\nDone...");
+}
+
+
+void loop()
+{
+  test_incr_decr();
+}
+
+
+void test_extremes()
+{
+  Serial.println(__FUNCTION__);
+  delay(10);
+
+  Serial.println("0");
+  pot.setValue(0, 0);
+  delay(2000);
+
+  Serial.println(MCP42XX_MIDDLE_VALUE);
+  pot.setValue(0, MCP42XX_MIDDLE_VALUE);
+  delay(2000);
+
+  Serial.println(MCP42XX_MAX_VALUE);
+  pot.setValue(0, MCP42XX_MAX_VALUE);
+  delay(2000);
+}
+
+
+//  connect all A GND and B 5V
+//  every W will have a different signal (same freq).
+void test_sinus()
+{
+  Serial.println(__FUNCTION__);
+  delay(10);
+
+  start = millis();
+  uint32_t i = 0;
+  while (millis() - start < 10000)
+  {
+    int8_t value = 127 * sin(i * TWO_PI / 100);
+    pot.setValue(0, 128 + value);
+    pot.setValue(1, 128 + value / 2);
+    i++;
+  }
+}
+
+//  straightforward sawtooth.
+void test_sawtooth()
+{
+  Serial.println(__FUNCTION__);
+  delay(10);
+
+  for (int i = 0; i < 255; i++)
+  {
+    pot.setValue(0, i);  //  auto wrap is fast...
+    pot.setValue(1, i++);  //  auto wrap is fast...
+    delay(100);
+  }
+}
+
+
+void test_incr_decr()
+{
+  Serial.println(__FUNCTION__);
+  delay(10);
+  pot.setValue(0, 0);
+  for (int i = 0; i < 255; i++)
+  {
+    pot.incrValue(0);
+    pot.incrValue(1);
+    delay(100);
+  }
+  for (int i = 0; i < 255; i++)
+  {
+    pot.decrValue(0);
+    pot.decrValue(1);
+    delay(100);
+  }
+}
+
+
+void test_timing()
+{
+  Serial.println(__FUNCTION__);
+  delay(10);
+
+  start = micros();
+  for (int i = 0; i < 1000; i++)
+  {
+    pot.setValue(0, i++);  //  auto wrap is fast...
+  }
+  stop = micros();
+  Serial.print("1000 x setValue():\t");
+  Serial.println(stop - start);
+  delay(10);
+
+  volatile int x = 0;
+  start = micros();
+  for (int i = 0; i < 500; i++)
+  {
+    x += pot.getValue(0);
+    x += pot.getValue(1);
+  }
+  stop = micros();
+  Serial.print("1000 x getValue():\t");
+  Serial.println(stop - start);
+  delay(10);
+}
+
+
+//  -- END OF FILE --
diff --git a/libraries/MCP4261/examples/MCP4261_performance/MCP4261_performance.ino b/libraries/MCP4261/examples/MCP4261_performance/MCP4261_performance.ino
new file mode 100644
index 00000000..e57ea985
--- /dev/null
+++ b/libraries/MCP4261/examples/MCP4261_performance/MCP4261_performance.ino
@@ -0,0 +1,117 @@
+//
+//    FILE: MCP4261_performance.ino
+//  AUTHOR: Rob Tillaart
+// PURPOSE: demo
+//     URL: https://github.com/RobTillaart/MCP4261
+//
+//  under investigation.
+
+#include "MCP4261.h"
+
+
+uint32_t start, stop;
+
+
+//  select, shutdown, dataIn, dataOut, clock == SOFTWARE SPI
+//  MCP4261 pot(10, 6, 7, 8, 9);
+
+//  select, shutdown, &SPI === HW SPI UNO clock = 13, data = 11
+MCP4261 pot(10, 6, &SPI);
+
+
+void setup()
+{
+  Serial.begin(115200);
+  Serial.println(__FILE__);
+  Serial.print("MCP4261_LIB_VERSION: ");
+  Serial.println(MCP4261_LIB_VERSION);
+  Serial.println();
+
+  SPI.begin();
+
+  pot.begin(0);  //  initial value
+  pot.setSPIspeed(1000000);
+  test_timing();
+  pot.setSPIspeed(2000000);
+  test_timing();
+  pot.setSPIspeed(4000000);
+  test_timing();
+  pot.setSPIspeed(8000000);
+  test_timing();
+
+  Serial.println("\nDone...");
+}
+
+
+void loop()
+{
+}
+
+
+
+void test_timing()
+{
+  Serial.println();
+  Serial.println(__FUNCTION__);
+  Serial.print("SPI:\t");
+  Serial.println(pot.getSPIspeed());
+  delay(100);
+
+  start = micros();
+  for (int i = 0; i < 250; i++)
+  {
+    pot.setValue(0, 42);
+    pot.setValue(1, 43);
+  }
+  stop = micros();
+  Serial.print("500 x setValue():\t");
+  Serial.print(stop - start);
+  Serial.print("\t");
+  Serial.println((stop - start) / 500.0);
+  delay(100);
+
+  volatile int x = 0;
+  start = micros();
+  for (int i = 0; i < 250; i++)
+  {
+    x += pot.getValue(0);
+    x += pot.getValue(1);
+  }
+  stop = micros();
+  Serial.print("500 x getValue():\t");
+  Serial.print(stop - start);
+  Serial.print("\t");
+  Serial.println((stop - start) / 500.0);
+  delay(100);
+
+  pot.setValue(0);
+  start = micros();
+  for (int i = 0; i < 250; i++)
+  {
+    pot.incrValue(0);
+    pot.incrValue(1);
+  }
+  stop = micros();
+  Serial.print("500 x incrValue():\t");
+  Serial.print(stop - start);
+  Serial.print("\t");
+  Serial.println((stop - start) / 500.0);
+  delay(100);
+
+  pot.setValue(255);
+  start = micros();
+  for (int i = 0; i < 250; i++)
+  {
+    pot.decrValue(0);
+    pot.decrValue(1);
+  }
+  stop = micros();
+  Serial.print("500 x decrValue():\t");
+  Serial.print(stop - start);
+  Serial.print("\t");
+  Serial.println((stop - start) / 500.0);
+  delay(100);
+}
+
+
+//  -- END OF FILE --
diff --git a/libraries/MCP4261/examples/MCP4261_performance/performance_0.1.0.txt b/libraries/MCP4261/examples/MCP4261_performance/performance_0.1.0.txt
new file mode 100644
index 00000000..75fc3f10
--- /dev/null
+++ b/libraries/MCP4261/examples/MCP4261_performance/performance_0.1.0.txt
@@ -0,0 +1,48 @@
+
+BOARD:  Arduino UNO
+IDE:    1.8.19
+
+MCP4261_performance.ino
+MCP4261_LIB_VERSION: 0.1.0
+
+HW SPI
+
+
+test_timing
+SPI:	1000000
+500 x setValue():	15404	30.81
+500 x getValue():	380	0.76
+500 x incrValue():	10776	21.55
+500 x decrValue():	10660	21.32
+
+test_timing
+SPI:	2000000
+500 x setValue():	11380	22.76
+500 x getValue():	384	0.77
+500 x incrValue():	8768	17.54
+500 x decrValue():	8640	17.28
+
+test_timing
+SPI:	4000000
+500 x setValue():	9400	18.80
+500 x getValue():	380	0.76
+500 x incrValue():	7768	15.54
+500 x decrValue():	7644	15.29
+
+test_timing
+SPI:	8000000
+500 x setValue():	8400	16.80
+500 x getValue():	376	0.75
+500 x incrValue():	7268	14.54
+500 x decrValue():	7140	14.28
+
+
+SW SPI
+
+500 x setValue():	107264	214.53
+500 x getValue():	380	0.76
+500 x incrValue():	56556	113.11
+500 x decrValue():	56432	112.86
+
+
+Done...
diff --git a/libraries/MCP4261/keywords.txt b/libraries/MCP4261/keywords.txt
new file mode 100644
index 00000000..e48e0142
--- /dev/null
+++ b/libraries/MCP4261/keywords.txt
@@ -0,0 +1,43 @@
+# Syntax Colouring Map For MCP4261
+
+# Data types (KEYWORD1)
+MCP4141	KEYWORD1
+MCP4142	KEYWORD1
+MCP4161	KEYWORD1
+MCP4162	KEYWORD1
+
+MCP4241	KEYWORD1
+MCP4242	KEYWORD1
+MCP4261	KEYWORD1
+MCP4262	KEYWORD1
+
+
+# Methods and Functions (KEYWORD2)
+begin	KEYWORD2
+reset	KEYWORD2
+pmCount	KEYWORD2
+
+setValue	KEYWORD2
+getValue	KEYWORD2
+
+incrValue	KEYWORD2
+decrValue	KEYWORD2
+
+setValueNV	KEYWORD2
+
+setSPIspeed	KEYWORD2
+getSPIspeed	KEYWORD2
+
+powerOn	KEYWORD2
+powerOff	KEYWORD2
+isPowerOn	KEYWORD2
+
+usesHWSPI	KEYWORD2
+
+# Constants (LITERAL1)
+MCP4261_LIB_VERSION	LITERAL1
+
+MCP41XX_MIDDLE_VALUE	LITERAL1
+MCP41XX_MAX_VALUE	LITERAL1
+MCP42XX_MIDDLE_VALUE	LITERAL1
+MCP42XX_MAX_VALUE	LITERAL1
diff --git a/libraries/MCP4261/library.json b/libraries/MCP4261/library.json
new file mode 100644
index 00000000..740ffc2e
--- /dev/null
+++ b/libraries/MCP4261/library.json
@@ -0,0 +1,23 @@
+{
+  "name": "MCP4261",
+  "keywords": "MCP4141,MCP4142,MCP4161,MCP4162,MCP4241,MCP4242,MCP4261,MCP4262",
+  "description": "Arduino library for MCP4261 SPI based digital potentiometers.",
+  "authors":
+  [
+    {
+      "name": "Rob Tillaart",
+      "email": "Rob.Tillaart@gmail.com",
+      "maintainer": true
+    }
+  ],
+  "repository":
+  {
+    "type": "git",
+    "url": "https://github.com/RobTillaart/MCP4261.git"
+  },
+  "version": "0.1.0",
+  "license": "MIT",
+  "frameworks": "*",
+  "platforms": "*",
+  "headers": "MCP4261.h"
+}
diff --git a/libraries/MCP4261/library.properties b/libraries/MCP4261/library.properties
new file mode 100644
index 00000000..1d2bf69f
--- /dev/null
+++ b/libraries/MCP4261/library.properties
@@ -0,0 +1,11 @@
+name=MCP4261
+version=0.1.0
+author=Rob Tillaart <rob.tillaart@gmail.com>
+maintainer=Rob Tillaart <rob.tillaart@gmail.com>
+sentence=Arduino library for MCP4261 SPI based digital potentiometers.
+paragraph=MCP4141,MCP4142,MCP4161,MCP4162,MCP4241,MCP4242,MCP4261,MCP4262
+category=Signal Input/Output
+url=https://github.com/RobTillaart/MCP4261
+architectures=*
+includes=MCP4261.h
+depends=
diff --git a/libraries/MCP4261/test/unit_test_001.cpp b/libraries/MCP4261/test/unit_test_001.cpp
new file mode 100644
index 00000000..7ff9eaae
--- /dev/null
+++ b/libraries/MCP4261/test/unit_test_001.cpp
@@ -0,0 +1,71 @@
+//
+//    FILE: unit_test_001.cpp
+//  AUTHOR: Rob Tillaart
+//    DATE: 2022-12-01
+// PURPOSE: unit tests for the A1301 magnetic sensor
+//     URL: https://github.com/RobTillaart/A1301
+//          https://www.adafruit.com/product/2857
+//          https://github.com/Arduino-CI/arduino_ci/blob/master/REFERENCE.md
+//
+
+// supported assertions
+// ----------------------------
+// assertEqual(expected, actual)
+// assertNotEqual(expected, actual)
+// assertLess(expected, actual)
+// assertMore(expected, actual)
+// assertLessOrEqual(expected, actual)
+// assertMoreOrEqual(expected, actual)
+// assertTrue(actual)
+// assertFalse(actual)
+// assertNull(actual)
+
+
+#include <ArduinoUnitTests.h>
+
+#include "Arduino.h"
+#include "MCP4261.h"
+
+
+unittest_setup()
+{
+    fprintf(stderr, "MCP4261_LIB_VERSION: %s\n", (char *) MCP4261_LIB_VERSION);
+}
+
+unittest_teardown()
+{
+}
+
+
+unittest(test_constants)
+{
+  assertEqual(64,  MCP41XX_MIDDLE_VALUE);
+  assertEqual(129, MCP41XX_MAX_VALUE);
+  assertEqual(129, MCP42XX_MIDDLE_VALUE);
+  assertEqual(257, MCP42XX_MAX_VALUE);
+}
+
+
+unittest(test_constructor)
+{
+  MCP4261 mcp(10, 6);
+  //  before begin.
+  assertEqual(2, mcp.pmCount());
+  assertEqual(0, mcp.getValue());
+
+}
+
+
+/*
+  TODO
+  setValue false test
+  setValue, getValue
+  incrValue
+  decrValue
+*/
+
+unittest_main()
+
+
+//  -- END OF FILE --
+