Low cost audio function generator(DDS)

[sougata]

Hi,

I need to design a low cost digital audio function generator. For the sinewave generation I would use a lookup table. To keep the control digital I need to scale (modulate) the peak sine values in software and softare PWM. Cannot use a PGA for cost restriction.
What is the best principal for that ?

I am restricted in terms of PIC throughput considering the soft pwm and other housekeeping functions. I must use a PIC16 @ 20MHz series to keep down the cost lower. So calculating the sine values on the fly (when doing a modulation) may eat up to much cycles to fit within the update routine

Please guide if it is at all possible and how ?

[mister_e]

Is there a specific reason why you want to use a PIC for that?

What is your frequency range?

[sougata]

Dear Steve,

Thanks for replying. Actually I live in a part of my country where sourcing of specialized components is a real problem. Initially I considered using a DDS chip. But set back due to unavailability. Frequency range is within 10K. I haven't done the homework yet. Just trying to get some guidelines whether to base it on a 16F. The possibility you can say. If it is technically possible then I might consider using a 18F too. That depends on the overall BOM cost.

[Acetronics2]

Hi, Sougata

ICL 8038, voltage controlled ??? ... you use the Pic as the freq regulator ... say, you build a simple PLL !!! but 8038 outputs some sinewaves ...

bad idea ???


Alain

[sougata]

Dear Alain,

Thanks for your reply. I just don't want to go the conventional (traditional)way. I have used MAX038 (big brother of XR8038) earlier but it was a pure analogue design with some fancy digital control as you mentioned. This project is all about low cost and best control. In fact with a PC side software the lookup tables could be modified to generate other waveforms as well. I am asking you guys for the possibility on a 16F. Storing one quadrant of data in the lookup table and building the sinewave is easy. But while modulating it, for a 8bit modulation index, I am doubtful on the processor througput considering 16/32 bit math. If there is an easy way out to do this in software please guide.

[Acetronics2]

Hi, Sougata

Here, you will find such a DDS module ... for the price ... just tears left !!!

http://shop.elv.de/output/controller...0&detail2=6325

or here, with a PC interface:

http://shop.elv.de/output/controller...&detail2=10617

Alain

[J. Mark Wolf]

Below is the link for an audio sine wave generator chip. Works good.

http://www.mix-sig.com/prodsh_MSLOSC.html

[Luciano]

Hi,

Low cost audio function generator?

Audio?

What about using the PC Sound Card as Signal Generator?
http://www.virtins.com/page2.html#Signal%20Generator

Tons of freeware available.

Best regards,

Luciano

[sougata]

Hi,

Thanks Luciano. I am aware of the Freewares available and the application is a product. However the issue is a little different. Its all about the scope of a 16F performing DDS. Without using much of additional circuitry.
Mark thanks for the link. The scope of the project does not permit to use it. Otherwise I would have gone for waveform generator chip. Also it is hard to find (if not impossible) in low quantities (less than 0.5K). If I at all go on with this project then I would be going for a 18F with a R-2R DAC.

[Acetronics2]

Hi, Sougata

a look at CYPRESS Application notes could give you the solution and soft ...

I know ... it's not PICs !!! but Free ICD and simple programmer.

Worth it !!!

Alain

[sougata]

Hi,

Thanks Alain for the info. I have played a little bit with the PSOC from cypress sometimes back. But not so skilled. I will though hunt the appnotes there and find out if the project is possible in low cost .