AD9850 Generate Random Fixed Frequencies Controlled By MEGA328P-AU

[Tigera]

Hey

I've made a circuit with AD9850 Controlled by ATMega328P-AU with serial interface.

Here is the Schematic Link.

[Moderator action: Link to external file server removed]


I've Tested Prog with AD9850 Module (HC-SR08_Module) and code is working.

Circuit use a 3.7v Single Cell Li-Po Battery and MT3608 to Boost 3.7v to 5v.

The Reference Oscillator for ad9850 is 2 MHz .

I've Reduce the code to just set the frequency of ad9850 But it generates few fixed random frequencies .

for instance:

Desire Freq ----> Output Freq

1 KHz ----> 900 KHz
2 KHz ----> 3.9 KHz

3 KHz ----> 15Hz

4 KHz ----> below 2Hz

5 KHz ----> 899 KHz



and so on.....



every time i change frequency , the output frequency is a random value between above.

I would appreciate any help.

 

[paulfjujo]

hello,

**broken link removed** with an Oscillator Quartz 125MHz !


light version to test AD9850 wich gives :
Init à 1Hz
Init à 1000Hz
Init à 5000Hz
Init à 20KHz
Init à 200KHz
Init à 1 MHz
with
float AD9850_FREQUENCY_FACTOR = 34.35973837; // 2^31 divided by 125MHz
4 294 967 296‬/125 000 000

main fonction to drive AD9850 (32 bits register to define frequency output)

void AD9850_Charge_Freq(float Freq)
{
AD9850_Serial_Data.TuningWord = (long) (Freq * AD9850_FREQUENCY_FACTOR);
SendSerialDataByteToAD9850(AD9850_Serial_Data.DDS. pv0);
SendSerialDataByteToAD9850(AD9850_Serial_Data.DDS. pv1);
SendSerialDataByteToAD9850(AD9850_Serial_Data.DDS. pv2);
SendSerialDataByteToAD9850(AD9850_Serial_Data.DDS. pv3);
SendSerialDataByteToAD9850(AD9850_CONTROL_WORD);
Delay_us(100);
FQ_UD = 1;
Delay_us(200);
FQ_UD = 0;
Delay_us(200);
}

with 2MHz you will get .
4 294 967 296‬/2 000 000 = 2147
means High resolution for low frequency , but short range in frequency

post your code ... to check the step value in frequency corresponding to the 32bits AD9850 register..