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Vishal -

For the ADS8558, please see the datasheet information on reading and writing to the configuration register (located at http://www.ti.com/lit/ds/symlink/ads8556.pdf ).

For the DAC7724, you can view the datasheet at http://www.ti.com/lit/ds/symlink/dac7724.pdf.  This device does not have control registers, so the part is controlled using external pins and the parallel data bus.

Hello again,

 I have been using the ADS8558 since a long time now...It was working very well but since last two days it is giving me constant output even though the analog input is changed.I saw if there was any short between the outputs but there is not and rest of the circuit is same.

I am using it in Hw mode with parallel output. I have kept CS as ground and am giving convert high  while read/write as low . I checked the busy signal output on MSO i am getting the output also but the parallel output remains constant even thought the input changes...

can you suggest what may be wrong???

Hi Vishal,

What is the state of your RESET pin?  if you toggle it high/low, does the ADS8558 provide the expected output data?

Initially when i was using i never gave anything to reset than also it used to give expected output. I made a new circuit yest and tested it and have included reset high/low also again the same result output remains same...and i guess its not the output of the analog input it is some random output which it gives. The thing is that i have a demo shortly and i thought everything is working fine till it stopped working so i am in a mess right can you help me in any manner?

Thn i thought may be this chip might be behaving in this manner so i changed the chip also but again the same output remains constant only....

Vishal -

Are you keeping to the timing with respect to Figure 3 and 4 in the datasheet?  You made the comment about setting CONVST while RD/WR are low...both of those signals are active low so you would want them to be high when issuing the CONVST.  You might want to verify this on your timing to make sure you these pins are set according to the previously mentioned datasheet figures.

I think so i am using it correctly since its the same code which made it work few days back.

my code is :(pins 0 and 2 are used for read and conv respectively)

 PORT = 0x05;

delay of 100 ms

PORT = 0x04;

delay of 100 ms

PORT = 0x05

delay of 100 ms

PORT = 0x01;

delay of 100 ms

Should i try Software mode????

Hello,

Finally i got the output now and the IC is working fine ...thanks a lot

Hi, 

May i ask you to have a copy of the VHDL code you use to drive the ADS855x in order to compare it with mine? Have you tried to drive the ADS855x at their maximum sampling frequency?

Thanks and best regards,

Goodmorning,

I'm just about to start a new data acquisition project in which i will use the ADS8568 driven by an FPGA ( i still haven't chosen which one to use ), is it possible to have

a copy of your VHDL code for this converter  in orfer to have s tarting point for my project?

Thanks in advance for your attention.

Regards.

Daniel.

Daniel -

Can you please start a conversation with me in which you include your email address? (This will prevent your email disclosure on the forum).

Once we have this information, we will be happy to provide you with the requested reference code.

I can give you the code but its a very rudimentary one if its fine with you...else yes code given by Greg is way better than mine...

Thank you very much Greg. I'll start it immediately.

Regards,

Daniel

Thanks for your concern Vishal.

Your code will be hepful too if you want to share it.

Regards,

Daniel.

HI Daniel,

  I am also using this ADS8568 ADC with spartan 3 FPGA. I have done Schematics And now i want to write verilog code  for the reading data.

 Could you please help me by providing the vhdl code to me if possible.

Thanks and regards

Sumit Sharma