[sdiy] 8253 modern replacement?

Tom Wiltshire tom at electricdruid.net
Sun May 10 16:36:11 CEST 2015


Thanks for the plug, but the VCDO is a rather different beastie. It's voltage-controlled for a start, and it's a wavetable oscillator, not a DCO.

I did look at doing a DCO on a PIC. The 16-bit timers on the 8-bit PICs don't offer much improvement over the 8253 (Juno 106 style) DCOs, so I decided to move to a dsPIC chip. That has 32-bit counters which makes the frequency accuracy much better, avoids stepping, and allows you to get super low frequencies without having to stick a divider after the clock (like the Juno 106 does).

I was later gratified to discover that Dave Smith used a similar dsPIC for the DCOs in the Prophet 08! The original discussion of that must be in the archive somewhere.

Tom

On 8 May 2015, at 18:05, MTG <grant at musictechnologiesgroup.com> wrote:

> Or this:
> 
> http://www.electricdruid.net/index.php?page=projects.vcdo
> 
> "A single chip 1V/Oct voltage controlled digital oscillator, with 20 waveforms in a scannable wavetable.
> The VCDO uses a PIC 16F1847 microprocessor to create a versatile and simple voltage-controlled 8-bit digital wavetable oscillator. All oscillator parameters are controlled by 0-5V control voltages. The chip has a native exponential control response, making interfacing with 1V/Oct control voltages very simple, even without an exponential convertor."
> 
> 
> On 5/8/2015 9:13 AM, Jack Jackson wrote:
>> Hmmm, thanks for all the suggestions. I'm wondering if the ATtiny85 arduino (8 pin DIP, 2 x PWM output) could be put to work. It's about the same cost. Maybe feed it the frequency it needs to hold as a byte over a serial line.
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