Sinewaves using interrupts.

[Jerson]

Hi Hank

If you're planning to use the digitally synthesised sine wave for audio purposes, please re-consider the number of samples. 16 samples are good enough to generate a sine wave for the CRO, but for the ear,.... well, it's a different game altogether.

I had used the DDS technique, albeit with a PSOC, to generate pure tones (sinewaves of fixed frequency) for a clinical audiometer. You will get a clean sine wave on the scope, but, the distortion present in the wave will make it unsuitable for any audio purist. So, I had to switch over to the AD9832 which should be quite similar in function to the 9835(I haven't checked)

The AD9832 is a 1024 point sampled wave DDS IC. The results I obtained from this are just excellent. Before this, I had used a ML2036 which is now obsolete.

You might achieve the tones, but, you may not like the sound you get using a 16 point DDS. Let me not discourage your collaborative effort, but look at it as a gentle helmet I've gifted you to save the remaining hair on your head LoL

Cheers

[HankMcSpank]

The AD9832 is a 1024 point sampled wave DDS IC. The results I obtained from this are just excellent. Before this, I had used a ML2036 which is now obsolete.

You might achieve the tones, but, you may not like the sound you get using a 16 point DDS. Let me not discourage your collaborative effort, but look at it as a gentle helmet I've gifted you to save the remaining hair on your head LoL

Hi Jerson,

Weirdly the AD9835 is available much cheaper on Ebay than the AD9832 - http://cgi.ebay.com.sg/AD9835BRU-Com...item35ac588755 )

Ok, I'll give part of it a go:

For a 5K signal with 32 samples, thats 32 x 5000 = 160,000/sec times to hit the interupt. With no real numbers to use here, lets say it takes 100 instructions to "hit" the int. So thats 1,600,000 ins/sec or 1.6mips. so to start off, i would think at a min 8 meg clock (2mips)

And what about generating such to two decimal places (eg 4999.22Hz) - what impact does that have on the number (100x more?)


Actually my intentions aren't particularly music driven, but while on that vein, here's someone pushing the PIC DDS (ADSR) envelope...



I actually totally agree about the moderation (a big high five from me)...it was just a bit of tongue in cheek - I too normally forget to answer the question (& for a good while, whenever I got presented with the coffee question I always got the answer wrong - I was just putting in the missing letter as the answer .....a case of RTFQ Hank!)

[Mike, K8LH]

I agree that if you're doin' audio you should look at one of the many DDS chips from Analog Devices. They used to be very nice about samples too, which I took advantage of when building a DDS Ham Radio project a few years ago.

Regards, Mike