AnsweredAssumed Answered

AD9959 SPI stops working after 20 bytes

Question asked by FirstSignal on Mar 13, 2017
Latest reply on Jul 5, 2017 by vandenplas


I'm trying to control the AD9959 chip via SPI using an Arduino (3.3 V version). I am able to send a few commands (upto 20 bytes), but after that the AD9959 does not update any further. I've tried something as simple as toggling between two different frequencies. This updates 4 times and then no longer changes. I can then only update after applying the reset trigger. 


A couple things I have tried without any success - 

1) Checked that it did not have to do with the SPI communication rate by turning it low.

2) Set the IO_Update trigger to be much longer than the SYNC_CLK period. I send an IO_Update after every command.

3)  Checked that it did not depend on which command I sent. I tried a combination of amplitude, frequency, PLL ratio control. In all these cases it updates only upto 20 bytes total

4) Checked that the Arduino output is still correct beyond 20 bytes.

5) The SYNC_IO pin is grounded


If anyone has insight into why this might be happening would be very helpful.


Thanks !