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AD9912 over SPI with PIC - I/O update not working

Question asked by Marduk on Dec 15, 2011
Latest reply on Mar 3, 2012 by Marduk

Hello,

 

I am trying to use a 16F876A PIC to send a FTW to an AD9912 Eval Board, and the SPI communication seems to be working fine according to the oscilloscope but it won't change the output frequency on the board. I suspect there is something wrong with the I/O update.

The part of the PIC C code that does the software update is:

 

                    PORTA.f1 = 0;  //CSB pin
                    SPI1_Write(0x00);  //Special function from MikroC library

                    SPI1_Write(0x05);
                    SPI1_Write(0xFF);
                    PORTA.f1 = 1;

 

Is this correct?

 

Also, I'm only using 4 pins that come from the PIC: SDIO, SDO, CSB and SCK. The pic runs at 10MHz with a crystal oscilator and SYSCLK comes from an external source at 1GHz.

 

My jumper configuration is:

 

JMP1: VDD

JMP2: ON (meaning that the jumper is in place)

JMP3: EXT

JMP4 to JMP7: VDD

JMP8: ON

JMP9: ON

JMP10: OFF

JMP11: OFF

 

I'm not using PLL or any other functions, I just want to test the FTW for now.

 

Thanks in advance!

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