AD9833 and oscilloscope - bad waveforms

Hello,
I’ve just got my AD9833 module


And I’ve managed to hook it up and run… but I’m unable to see the waves correctly on my oscilloscope (digital)…
Probably I’m connecting sth wrong, but I’ve no clue what…
As I connect some speaker and play with a frequency and mode (sin, sqr, trg) I can hear the diffrence, but on the oscilloscope (which I connected to output and ground of AD9833) shows me some very high frequency (~20MHz) crap… It seems to me, that it takes the inner AD9833 frequency from clock, which is 25MHz - but still, I’ve no idea what to do…

/*
  AD9833 Signal Generator
  
  Connections to the AD9833 are:
  
  AD9833    MEGA    UNO   Signal Name
  REF                     Output of AD9833 onboard 25MHz clock
  VCC       5V      5V
  DAT       51      11    MOSI
  CLK       52      13    SCK
  FNC       53      10    SS (Any digital pin can be used as long as this pin remains as output)
  GND       GND     GND
  OUT                     AD9833 signal ouput

  Frequency formula
  f = ΔPhase × f_MCLK / 2^28 
*/

#include <SPI.h>

#define AD9833_F_MCLK 25000000          // 25MHz clock
#define AD9833_2POW28 268435456         // 2 to the power of 28

#define FSYNC 10

void setup(){
  Serial.begin(115200);
  
  SPI.setDataMode(SPI_MODE2);           // SPI Mode 2 for AD9837
  SPI.begin();
  digitalWrite(FSYNC, HIGH);
  pinMode(FSYNC, OUTPUT);               // FSYNC
  
  //Initial frequency
  double freq = 4000.0;
  
  AD9833_Control(0x100);                // Reset
  AD9833_Freq(freq);
  AD9833_Phase(0);

// Release reset
  //AD9833_Control(0x0000);               // sine
  //AD9833_Control(0x0020);               // square
  AD9833_Control(0x0002);               // triangle

  Serial.print("Frequency is ");
  Serial.println(freq);
}

void loop(){}
  
void AD9833_Control(uint16_t control){
  control = control & 0x3FFF;           // Mask off upper 2 bits so we are writing to control register
  control = control | 0x2000;           // Ensure the B28 control register bit is set
  digitalWrite(FSYNC, LOW);             // Set FSYNC low
  delayMicroseconds(5);
  AD9833_Write(control);
  digitalWrite(FSYNC, HIGH);            // Set FSYNC high
}

void AD9833_Freq(double freq){
  uint32_t frequency = (uint32_t)(((double) AD9833_2POW28 / (double)AD9833_F_MCLK * freq));
  digitalWrite(FSYNC, LOW);             // Set FSYNC low
  delayMicroseconds(5);
  AD9833_Write(0x4000 | (0x3FFF & (uint16_t)(frequency)));
  AD9833_Write(0x4000 | (0x3FFF & (uint16_t)(frequency >> 14)));
  digitalWrite(FSYNC, HIGH);            // Set FSYNC high
}

void AD9833_Phase(uint32_t phase){
  digitalWrite(FSYNC, LOW);             // Set FSYNC low
  delayMicroseconds(5);
  AD9833_Write(0xC000 | (0x1FFF & (uint16_t)(phase)));
  AD9833_Write(0xE000 | (0x1FFF & (uint16_t)(phase>>12)));
  digitalWrite(FSYNC, HIGH);            // Set FSYNC high
}

void AD9833_Write(uint16_t value){
  SPI.transfer(highByte(value));
  SPI.transfer(lowByte(value));
}

I’ve grabbed code of above from this forum, and connected everything as described in the beginning (I have Arduino Uno R3).
Should I do sth with REF?
Probably it just some stupid mistake, so sorry, but I’m quite a newbie if it comes to oscilloscope…
Thanks in regard!