Sequencer

[livingston]

I've been interested in having a sequencer to control parameters in the FV-1. I tried to code up something but it failed miserably.

Basically, I want to be able to have a time-varying sequencer that steps through 3 or 4 values, then goes back to the beginning of the sequence. A pot would control the amount of time between steps, and the values to step through would be predetermined in the program. I figured it would go something like this

1 load a register with -1
2 add .0001 every sample
3 when the number goes positive, add x [x= the parameter value of step 1]
4 write to parameter
5 SOF back to -1
6 repeat 1-5

The problem is (even if this worked), it would never repeat, it would just add to the parameter over and over which would quickly clip to 1.999...

So I don't think this is the right approach. Any thoughts?

[frank]

Well, you just need to reset the counter/parameter/whatever when it hits terminal count. Maybe something like:

initialize count to -1 (using skp run)

count = count + 0.25
if count >= 0 count = -1
if count == -1, set param = a
if count == -.75 set param = b
if count == -5 set param = c
if count == 0 set param = d

Code here that uses param

If you add to param then you will need to check if it exceeds a value and reset it if it does.

[livingston]

How would I code the statements like "if count = -5"? Would that use the AND opcode?

[frank]

Since there is no "if" statement in FV-1 you need to deduce the value of a register, something like:

(assume CTR is a register, it holds a number from -1 to 0, 0 or + is a terminal condition where the register is reloaded with -1 and all that logic is above this code)

Code: Select all

clr             ; clear the ACC
rdax   CTR,1.0    ; read CTR
sof 1,0.25         ; add 0.25
skp   gez, param1   ;skip to routine to load param 1 if >= 0
sof 1,0.25         ; add 0.25
skp   gez, param2   ;skip to routine to load param 2 if >= 0
sof 1,0.25         ; add 0.25
skp   gez, param3   ;skip to routine to load param 3 if >= 0
sof 1,0.25         ; add 0.25
skp   gez, param4   ;skip to routine to load param 4 if >= 0

param1:
clr
or 0x7fffff
wrax param,0
skp gez, algo

param2:
clr
or 0x3fffff
wrax param,0
skp gez, algo

param3:
clr
or 0x1fffff
wrax param,0
skp gez, algo

param4:
clr
or 0x0fffff
wrax param,0
skp gez, algo


algo:
; put the routine here and use param reg as the coefficient/etc.

I have not tested the above code but it should work (ok, probably a typo or two) and there are things you may be able to do to shorten it if the coefficients are related in some fashion.

[Alex MAK]

Hi, guys! Please tell me how to make it work. For example to make it work with tremolo. Thank you! Best regards, Alex!

[livingston]

Alex, as Frank says at the end of his code, put your tremolo code after, then use the "param" register as your sequenced value. You could apply this to volume to make a random "tremolo" or you could apply it to the speed of the tremolo.

[Alex MAK]

I want to apply it to the speed of the tremolo. To speed sequencer operated POT0. I tried to do this but my attempts do not work.

Code: Select all

equ	mono	reg0
equ	trem	reg1
equ	param	reg2
;equ	CTR	reg3		

clr             ; clear the ACC 
rdax   pot0,1.0    ; read CTR 
sof 1,0.25         ; add 0.25 
skp   gez, param1   ;skip to routine to load param 1 if >= 0 
sof 1,0.25         ; add 0.25 
skp   gez, param2   ;skip to routine to load param 2 if >= 0 
sof 1,0.25         ; add 0.25 
skp   gez, param3   ;skip to routine to load param 3 if >= 0 
sof 1,0.25         ; add 0.25 
skp   gez, param4   ;skip to routine to load param 4 if >= 0 

param1: 
clr 
or 0x7fffff 
wrax param,0 
skp gez, algo 

param2: 
clr 
or 0x3fffff 
wrax param,0 
skp gez, algo 

param3: 
clr 
or 0x1fffff 
wrax param,0 
skp gez, algo 

param4: 
clr 
or 0x0fffff 
wrax param,0 
skp gez, algo 


algo: 
; put the routine here and use param reg as the coefficient/etc. 

rdax	adcl,1
rdax	adcr,1
wrax	mono,0	;attenuate into reverb

rdax	param,1		;get control pot
mulx	param		;square function
sof	0.4,0.1		;scale rate to reasonable range
wrax	sin1_rate,0	;write to sin1 rate register

cho	rdal,sin1		;get sinewave, +/-0.5
sof	1,0.5		;add 1/2 to get sinwave that swings 0 to 1
wrax	trem,0		;write tremelo modulation signal

rdax	mono,0.5	;attenuate signals so as not to clip
mulx	trem
sof	0.75,0		;boost tremelo to maintain average amplitude
rdax	mono,-0.5
mulx	pot2		;crossover between input and tremelo with pot2
rdax	mono,0.5
sof	1.999,0		;recover gain
wrax	dacl,1
wrax	dacr,0