MCP41100 only 63K ????

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1

Hi, i tried use digital potenciometer MCP41100 code from: http://www.instructables.com/id/Digital-Potentiometer-MCP41100-and-Arduino/

/*
this program taken from arduino Example .
  modified by By Mohannad Rawashdeh
  http://www.genotronex.com
https://www.instructables.com/

  This code used to control the digital potentiometer
  MCP41100 connected to  arduino Board
  CS >>> D10
  SCLK >> D13
  DI  >>> D11
  PA0 TO VCC
  PBO TO GND
  PW0 TO led with resistor 100ohm .
*/
#include <SPI.h>
byte address = 0x11;
int CS= 10;
int i=0;

void setup()
{
  pinMode (CS, OUTPUT);
  SPI.begin();
  // adjust high and low resistance of potentiometer
  // adjust Highest Resistance .
   digitalPotWrite(0x00);
   delay(1000);
 
      // adjust  wiper in the  Mid point  .
   digitalPotWrite(0x80);
   delay(1000);

   // adjust Lowest Resistance .
   digitalPotWrite(0xFF);
   delay(1000);
}

void loop()
{
    for (i = 0; i <= 255; i++)
    {
      digitalPotWrite(i);
      delay(10);
    }
    delay(500);
    for (i = 255; i >= 0; i--)
    {
      digitalPotWrite(i);
      delay(10);
    }
}

int digitalPotWrite(int value)
{
  digitalWrite(CS, LOW);
  SPI.transfer(address);
  SPI.transfer(value);
  digitalWrite(CS, HIGH);
}

The problem is in max resistance - I measured only about 63-83kOhm. I tested 3 pcs of this chip ...

For better measurements, we've modified the code so that we can measure min and max in 'loop' to:

void loop()
{
   
      digitalPotWrite(255);

     delay(2000);
     digitalPotWrite(1);
delay(2000);

}

The result was exactly the same, measured around 83-63 ohms
I need to use a range of 0-100k ohm ...

I tested on board UNO and Nano V3, both with controller ATmega328P

I do not know what I'm doing wrong :frowning: