Hi Tolga,

you write about an interesting PIC Project. I have no real solution for a Delta-Sigma with 256x oversampling on PIC16xxx, but some suggestions:

After oversampling the analog signal you need digital filtering to reduce the noise and to achive 16Bit resolution. Digital filters are the main Job of DSPs, so consider to use a DSPic (or a better DSP, if you need a higher sampling rate).

I remember some application notes about digital filters on DSPIC in the web, some with C-Code exampels. Google the www websites for more details about it.

kind regards,

Hans-Rainer

Thanks Hans. Your thoughts are close to my initial thoughts, however, here is what I THINK the story is:

*** First, you do not need a digital filter, since you can do simple-and-silly averaging which will give you a sinc() response in the frequency domain, but, the side lobes are so small that, it is good enough,

*** Second, since you are already reducing your FINAL data rate so much (256x), you need 256x fewer computations, so, even an 8bit PIC can keep up with such simple operations as averaging.

*** Filtering is on both ends (i.e., input, and output). I want to know what happens in the middle (i.e., the heart of the operation)

Hi,

Your ref. is OK but perhaps:

Aziz PM, Sorensen HV, Van der Spiegel J. An overview of Sigma-Delta converters. IEEE Signal Processing Magazine Jan. 1996; 13:61–84.

is more clear on the architectures needed.

Anyway the S-D precedes the quantizer, i.e. your AD, so it should be implemented in analog hardware.

In your ref only one bit S-Ds are considered and the 1 bit DAC needed is straightforward, but in your case a 12 bit DAC is needed.

sim

@Simone, I read this paper. It is clearly much better than my example. IT looks like one of the fundamental papers that put it all together ,,, However, it still doesn't sound to me like, the intent was never to use PURE SOFTWARE at any point in time ... So, I will have to adapt it.

you can build this project with DSM oredr 2 and minimum osr 108 for A/D 16bit resolution(of course ideal !!).

i put simulink and code with matlab in pdf for you,i hope my answer is value.

good lock.

patch DSM matlab