Multiple ad9833s

Projects General Guidance
1

I am new to this. I have found some nice code on here to talk to a AD9833 sine wave generator. I need 8 sine waves in the 200 khz range. I have 8 each AD9833 chips.
I am confused about a couple of things. The chips claim to be low power. I see a mention about 2 channels although they only have one output pin. There are 2 frequency registers and 2 phase registers. Once I set these I do not need to change anything. They use an SPI interface which I think I understand to some extent.
In my beginner mind I am thinking that I can wire the chips in parallel and just use different data pins from the Nano for slave select lines. That way I could set each and then move on to the next. I have a couple of questions.
How many lines can I use before I load the controller down?
If I figure out how to switch the 2 channels in the 9833 what would be the maximum rate?

Thanks in advance for any help. I am just beginning this project. You guys helped me a lot on stage one which was a square wave generator.

This is all really fun and stressful at the same time. The syntax is troublesome to a newcomer/ non programmer.

2

Hi,
The AD9833 has only one waveform output.

There are 2 frequency registers and 2 phase registers. Once these are set, you can select which frequency/phase is used for output by selection bits in the control register.

You can use multiple devices by connecting all SCLK and SDATA pins to Arduino SPI SCK and MOSI and use separate data output pins ('slave select') to each AD9833's FSYNC pin.

It should handle 15MHz SPI so you could write a control word in around 1uS, so the speed at which you could write different control bits will be limited by the speed of your program. With a tight loop you could probably switch between two frequencies at more than 10kHz.

The difficult part will be making a PCB for eight AD9833's and providing master clock to them all.

Yours,
TonyWilk