After experimenting I’ve had a radical redesign. Using SRAM I’ve been able to sack off loads of circuitry simplifying the layout and reducing parts count! Added bonus include the improved features such as more memories. I’ve been trying to get a prototype layout sorted too. There are a few controls to add (the knob for the gate logic is there but it’s not connected; it’s all tested and working tho) just the core of the note sequencing.
I’ve not thought much about the analogue side; at the moment I’ve got 16 multitude presets that set the discrete voltages per step. Works fine.
The digital side of the gate generation is sorted but for a bit of finishing on the control side. So far it’s set by a 5 position switch with settings for mute, gate, gate x2, gate x4, gate x8 on a per step basis for ratcheting/repeating etc. The master clock (which selects the note data sent to the DAC) will have a division factor independent of the gate multiplier for ‘stretching’ pattern note data past 16 steps. I might be able to incorporate that on a setting per step basis too but I might have to sacrifice that as the bit count is maxed out. Might re jig. One bonus is that the way the design works you’re just saving bits per step…those bits can control anything but can also be as wide as you need as long as you don’t exceed the 8 bit limit. To get around that would require shift registers and make the control side more complex… it would be easier just to ‘break into’ more SRAM.
Old design
New design.
Knobs are for setting note and gate value respectively. Red button toggles programming mode, green is reset and black is advance step. So it’s a case of select prog mode, set up your note and gate values, press advance and repeat until all 16 steps are programmed. Toggle back out of prog mode and the advance button doubles as play.
Point is that’s all gravy, the basic principle works and is tested. I’m messing about with old pulled SRAM chips but looking at current data sheets tells me my basic design will work with them too. I’ve been rooting about in the stock pile and I’ve found a few more chips, one that, if I swap it out with the one I’m using, should give me 64 steps per pattern, basically with the addition of a couple more logic chips. Don’t you love being green?