DS1077 + Arduino

I've finally had a chance to get around to playing with the DS1077 configurable oscillator!

The circuit to get it working is very simple, just hook up the Ardiono as the I2C master, I used a 10K pullup resistor on both the SCL and SDA lines.  I tied CTR0 and CTR1 on the DS1077 to GND to enable the chip all the time.  For the following video, I put the scope probe onto the OUT1 pin...

Here's a quick schematic for that hastily breadboarded demo circuit...

I like the pinout of this chip, as it clearly demonstrates deference to signal integrity design considerations for the PCB designer.  Notice how the VCC and GND pins are side by side.  That makes it very convenient to place a decoupling cap right on those lines as close to the chip as possible.

#include 

const int ds_address = 0xB0 >> 1; //DS1077 default address

#define MUX_HI_PDN1_BIT (B01000000)
#define MUX_HI_PDN0_BIT (B00100000)
#define MUX_HI_SEL0_BIT (B00010000)
#define MUX_HI_EN0_BIT  (B00001000)
#define MUX_HI_0M1_BIT  (B00000100)
#define MUX_HI_0M0_BIT  (B00000010)
#define MUX_HI_1M1_BIT  (B00000001)

#define MUX_LO_1M0_BIT             (B10000000)
#define MUX_LO_DIV1_BIT            (B01000000)

#define BIT_ON (0xff)
#define BIT_OFF (0x00)


void setup()
{
  Wire.begin();
}

void loop()
{
  long i;
  for(i = 0 ; i <= 1025 ; i+=1)
  {
    i2c_write(ds_address, 0x02, 
      ( 0
        | (MUX_HI_PDN1_BIT & BIT_OFF)
        | (MUX_HI_PDN0_BIT & BIT_OFF)
        | (MUX_HI_SEL0_BIT & BIT_ON)
        | (MUX_HI_EN0_BIT  & BIT_ON)
        | (MUX_HI_0M1_BIT  & BIT_ON)
        | (MUX_HI_0M0_BIT  & BIT_ON)
        | (MUX_HI_1M1_BIT  & BIT_ON)
      )
      ,
      ( 0
        | (MUX_LO_1M0_BIT  & BIT_ON)
        | (MUX_LO_DIV1_BIT & BIT_OFF)
      )
    ); //mux
    delayMicroseconds(100);    

    i2c_write(ds_address, 0x01, (i >> 2), (i << 6) & 0xC0); //div
    delayMicroseconds(100);
    i2c_write(ds_address, 0x3F);

    delayMicroseconds(10000 - i);
  }  
}

void i2c_write(int device, byte address) {
     Wire.beginTransmission(device); //start transmission to device 
     Wire.write(address);        // send register address
     Wire.endTransmission(); //end transmission
}

void i2c_write(int device, byte address, byte val1) {
     Wire.beginTransmission(device); //start transmission to device 
     Wire.write(address);        // send register address
     Wire.write(val1);        // send value to write
     Wire.endTransmission(); //end transmission
}

void i2c_write(int device, byte address, byte val1, byte val2) {
     Wire.beginTransmission(device); //start transmission to device 
     Wire.write(address);        // send register address
     Wire.write(val1);        // send value to write
     Wire.write(val2);        // send value to write
     Wire.endTransmission(); //end transmission
}

This chip lets you output a 50% duty cycle square wave at any frequency given by 133,000,000 divided by any number between 1 and 1025 inclusive.  This divider is selected by sending a short I2C sequence to the chip from whatever microcontroller you prefer.  I'm using an Arduino here because there was some code easily available for it.  For my final purposes I'll be using a P8X32A Propeller to drive this chip.

This is a fun chip to mess with and has some substantial benefits for the advanced Parallax Propeller user, since this will let you experiment with letting the Propeller chip overclock itself on the fly!  Granular clock management and tuning is something I'm interested in experimenting in with the Prop and this chip will be a great way to do it!

I think this chip will also be of use to Ham radio enthusiasts because of it's frequency modulation abilities.  Although I suspect that it's stepped frequency brackets are a bit of a limitation for some of the really advanced shenanigans of the Ham community, this would be useful for some kind of carrier modulation or FDM projects.

Anyway, sorry for the long-winded post - hope you find this useful or at least interesting.

Wardy.