Has anybody used the DAC in the new Nu Horizons Spartan 3 development board

Dear Makesh,

I have had some small problems with the LTC1654 as well. Have you also started with the DAC A output?

There is a small problem with the output gain configuration of the LTC1654. There is one pin per DAC which should be either connected to GND or to the DAC output - if I remember correctly. On the board the DAC A config pin is hardwired to VCC and the DAC B config pin is connected to VCC by a resistor but can be shorted to GND by a 2-pin jumper close to the DAC.

If you close the jumper at least DAC B should work. To make DAC A running you have to lift the corresponding pin of the LTC1654 and connect it to GND with a short wire. There is one capacitor connected to GND close to that pin. This is a suitable point to get the GND signal from.

I hope it helps. I guess you have the datasheet of the LTC1654, please look for the gain setting for detailed infos.

I like the compact board, also because of its on board peripherals.

Best regards,

Christoph

Hi Christoph,

Thanks a lot for bringing that to my attention. Inspite of using a jumper for channel B and the changing the code for channel B I still get a 0 voltage output. I think I am running into some timing issues.

Did you use the 24 bit or 32 bit load sequence ? If possible could you post first few lines and last few lines of the dac controller code.

Thanks once again for your prompt post. I was about to use another D/A

Thanks Makesh

Dear Makesh,

I will send you a pice of code which will toggle DAC A and DAB B output with no addional requirements tomorrow. I have used the 24 bit mode. Concerning the DAC the update rate is 900ks/s. If you run both DACs in parallel it ends up at approx. 450ks/s each. Its just about how to write data sheets... BTW: The user constraints file is ok? Have you checked the DAC input lines with a scope?

Best regards and please rinind me if you dont receive the file,

Christoph