Has anybody used the DAC in the new Nu Horizons Spartan 3 de

[Makesh Soundarajan]

Hi

Has anybody used the D/A converter (Linear Tech's LTC1654) ? I am
having few issues . I tried to initialize using both the 24 and 32 bit
format but the output of D/A remains at 0.

Any help will be greatly appreciated


Thanks
Makesh

 

[Christoph Brinkhaus]

Makesh Soundarajan <makesh_s_e@hotmail.com> wrote:

Dear Makesh,

Hi

Has anybody used the D/A converter (Linear Tech's LTC1654) ? I am
having few issues . I tried to initialize using both the 24 and 32 bit
format but the output of D/A remains at 0.

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.

Any help will be greatly appreciated

I hope it helps. I guess you have the datasheet of the LTC1654,

please look for the gain setting for detailed infos.

Thanks
Makesh

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

Best regards,

Christoph

 

[Makesh Soundarajan]

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


Christoph Brinkhaus <c.brinkhaus@t-online.de> wrote in message news:<r40fcc.ql.ln@lola.de>...

Makesh Soundarajan <makesh_s_e@hotmail.com> wrote:

Dear Makesh,

Hi

Has anybody used the D/A converter (Linear Tech's LTC1654) ? I am
having few issues . I tried to initialize using both the 24 and 32 bit
format but the output of D/A remains at 0.

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.

Any help will be greatly appreciated

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

Thanks
Makesh

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

Best regards,

Christoph

 

[Christoph Brinkhaus]

Makesh Soundarajan <makesh_s_e@hotmail.com> wrote:

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

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


Makesh Soundarajan <makesh_s_e@hotmail.com> wrote:

Dear Makesh,

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

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.