AD1939 Sigma Studio Comms Failed

Hello MDThommo81,

The AD1939 only has an SPI control port for writing and reading back of the internal control registers, Since the USBi's I2C LED in your picture was flickering, which leads us to believe that you are using I2C in the hardware setup window in Sigma Studio. Please make sure that it is set for SPI like below.

Note that I chose SPI 0x2 ADR0, because I was using one of the extra latches. The USBi pin uses latch 1 which is SPI 0x1 ADR0. please select that.

If you change that to correct latch, then read/write like this to see whether communication was established: simply right-click the AD193X block, choose READ/WRITE window, modify the address, write any register value and then read it back. You can verify if you are reading the written data correctly.

we would also need to look at your hardware schematic, what is the state of the reset pin? 

If you have a scope, just probe signals coming out of the USBi and see if it makes sense or just see 'is there a signal coming out in the first place. 

Also please go thru this PCB layout best practices manual.

PCB Layout Best Practices for AD193x codecs - Q&A - Audio - EngineerZone (analog.com)

Regards,

Harish

sorry, forgot to include my circuit schematic. see attached. Thanks!

PDF

Hello Mark,

Since the USBi block in your schematic is red in color, I believe your PC driver is not loaded correctly. once The USBi is connected properly to your PC then the USBi block will turn green, as shown in the image below.

The USB cable may be the issue. Retry after changing the cable. Try these actions listed below if you continue to have this issue.  

1. Un-install any version of Sigma Studio that was previously installed

2. Re-start your PC

3. Install sigma studio V4.7

4. Again, restart your pc

I hope this works.

Regards,

Harish

Hello MDThommo81,

Follow the suggestions that Harish has been giving you. He is providing great help. I just want to comment on one thing I noticed in your schematic. You are direct coupling the DAC outputs to an amplifier. You are taking the CM voltage from the codec and going to an OpAmp to drive the output amplifier reference which is all great to do. The issue is you have the OpAmp setup as a non-inverting amplifier so the output will be 1+Rfb/Rin. So the 1,5V CM will and up being 3V and you actually labeled the test point as 3V. This will skew the CM voltage on the output of the DACs and cause distortion and headroom issues and in fact there may not be much output at all or only half the waveform. You need to remove R163 and change R162 to be a 0-ohm jumper and that will leave you with a voltage follower configuration which is perfect to use for this application. 

Dave T

Brilliant, thanks Harish. I'm away for work right now but will try again tomorrow when I'm back at the home office.

Brilliant, thanks Harish. I'm away for work right now but will try again tomorrow when I'm back at the home office.