Using the Hardware Quadrature Encoder Channel on the DUE

Hardware Arduino Due
89

Hi folks, summarizing from above, this is the minimal setup for using a two pin encoder as a knob on channel TC 0, Channel 0:

void setup() {

  pmc_enable_periph_clk(ID_TC0);
  TC_Configure(TC0,0, TC_CMR_TCCLKS_XC0);  
  
  TC0->TC_BMR = TC_BMR_QDEN          // Enable QDEC (filter, edge detection and quadrature decoding)
                | TC_BMR_POSEN       // Enable the position measure on channel 0
                //| TC_BMR_EDGPHA    // Edges are detected on PHA only
                //| TC_BMR_SWAP      // Swap PHA and PHB if necessary (reverse acting)
                | TC_BMR_FILTER      // Enable filter
                | TC_BMR_MAXFILT(63) // Set MAXFILT value 
               ;                       

  // Enable and trigger reset
  TC0->TC_CHANNEL[0].TC_CCR = TC_CCR_SWTRG | TC_CCR_CLKEN;
  
}

void loop() {
  int16_t count = REG_TC0_CV0;
}

This will return a positive or negative count. Note it will roll over at plus or minus 32767. In theory, you can avoid rollover by resetting the count to zero by calling

TC0->TC_CHANNEL[0].TC_CCR = TC_CCR_SWTRG | TC_CCR_CLKEN;

But in reality, this does not seem to quite get back to zero all the time. I just check to see if I am above 32000, or below -32000, and reset.

Hope this helps.
Doug