Adc

[lucianofalbo]

Can somebody help me with the code for an ADC? I just need an example...
Thanks.

 

[jeppe]

First must you accept - its not possible to connect an analog signal direct to a digital system like a FPGA.
But you could generate a known analog value with a DAC component and use this together with an analog comperator.

Visit this page in order to learn more about PWM and PPM.
http://www.jjmk.dk/MMMI/Exercises/05_Counters_Shreg/No7_PWM_vs_SigmaDelta/index.htm

Jeppe

 

[lucianofalbo]

Thanks very much! I will look at the link and try to understand what to do!
Bye
Luciano

 

[lucianofalbo]

last week i had not enough time to read accurately your documentation. I will do it in this week. Anyway please answer to this question:
Is it possible using only an FPGA (I have a spartan3) to realize a DAC?And a ADC?
Thanks

 

[jeppe]

Yes - Its possible to create a DAC with a FPGA, the digital output which modulated with PWM or PPM must however drive a buffer (OpAmp etc) and the perhaps will a simple analog filter be useful as well.

With help from this DAC output (which you control) can you build an ADC by adding an analog comperator to the design. The output from the comperator must be feed back to the FPGA.
The most efficent way to make a conversion will be the Succesiv Approximation algoritm.
Hope this was useful
Jeppe

 

[lucianofalbo]

I have read the block diagram for the PPM DAC in your link but there is something basic I don't understand. What is the digital value to be converted?Is it PCM? How can I obtain an analogic value using PPM that is a std_logic(in other words can you be more detailed talking about a "buffer")?
I know it's fault of my digital/analog ignorance but I ask you if you can explain the DAC architecture using that block diagram, from the digital input to the analog output.
Bye

 

[jeppe]

Well - seems Im not that busy right now
Take a look at this page and let me know if its useful.

http://www.jjmk.dk/MMMI/Exercises/05_Counters_Shreg/No8_ADC_conversion/5_8_adc_with_fpga.htm

Jeppe

 

[lucianofalbo]

Maybe I begin understanding something...then to make only a simple DAC I have to send the digital word that i want to convert to a PPM generator and send the PPM pulse to an analog low pass filter. Isn'it?
Thanks