AnsweredAssumed Answered

AD9834 Doesn't Respond to SPI Commands

Question asked by PAnnenkov on Mar 20, 2013
Latest reply on Mar 27, 2013 by Kevin.G

Dear Experts,

 

I am trying to configure the AD9834BRUZ to output 6.08064 MHz (FREQ0) and 5.91936 MHz (FREQ1) using a 7.3728 MHz MCLK and a 2.5V power supply.

 

I am having trouble getting the AD9834BRUZ under control. No matter what I write to it over SPI, it just outputs a strange 1.4MHz output on IOUT and IOUTB pins and 4MHz square wave on SIGN BIT OUT pin (both oscilloscope screenshots are attached). It outputs the same waveforms on power on before I write anything over SPI, so my commands have no effect.

 

I calculated the following values for the registers:

FREQ0=0x0d3220c8

FREQ1=0x0cd88748

PHASE0=0

PHASE1=0

 

I attached the schematic so you can see how the hardware is configures.

I attached the code showing the sequence and the values that I am writing into the AD9834.

I attached an oscilloscope screenshot of the SPI Control Register write so you can see how the SPI is configured. (CH1=FSYNC, CH2=SCLK, CH3=SDATA)

 

Please let me know if I can add anything to help with troubleshooting.

 

Thanks in advance for your help,

Pavel.

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