With help from efox29 I worked out to control the MAX5483(http://www.kynix.com/uploadfiles/pdf2286/MAX5483ETE2b.pdf), 10-bit digital potentiometer (data sheet here) with an arduino using SPI. Now how can I trigger more than one value?
I tried to do that with a simple for-loop, but it doesn’t work. To be precise it produces a strange resistance value (68 Ohm). And even just putting a delay seems to cause the same issues…
For example
digitalPotWrite(197); //
delay(10000);
digitalPotWrite(60); //
delay(10000);
Should change the resistance between 2.1k Ohm and 688 Ohm. I assume that, since by putting just
digitalPotWrite(197);
or
digitalPotWrite(60);
alone without delay(10000); I can measure this values with my multimeter between the pin 10 and 11 of MAX5483. But by putting it all together like I tried above, I strangely measure only 65-68 Ohm. This doesn’t change by only putting the following lines:
digitalPotWrite(197); //
delay(10000);
Here the measured value (between pin 10 and 11) is still 68 Ohm… Here is the complete code:
#include
const int csPin = 3;
const int selPin = 2;
void setup() {
SPI.begin();
SPI.setBitOrder(MSBFIRST); //We know this from the Data Sheet
SPI.setDataMode(SPI_MODE2);
pinMode(csPin,OUTPUT);
digitalWrite(csPin, LOW);
pinMode(selPin,OUTPUT);
digitalWrite(selPin, HIGH);
}
void loop()
{
//“sweep” small range (from 1.7 to 2.1 KOhm)
// 158 to 197
//
// for (int i=158; i < 211; i++){
// delay(1000);
// digitalPotWrite(i); //
// }
digitalPotWrite(197); //
delay(100); // seems to cause issues… without this line it works
}
void digitalPotWrite(int value) {
digitalWrite(csPin, LOW);
delay(1);
byte command=0x0;
byte byte0 = (value & 0x03) << 6;
byte byte1 = (value & 0x3FC) >> 2;
SPI.transfer(command);
SPI.transfer(byte1);
SPI.transfer(byte0);
delay(1);
digitalWrite(csPin, HIGH);
}