Ahle's signal generator triangle wave code
David B
Posts: 592
I'm looking for some pasm triangle wave code.
I've gotten Johannes Ahlebrand's signal generator code trimmed down to almost the simplest form that still generates a nice clean triangle in the same way as his original generator module did, but there's a programming trick in it that I just don't get.
In this code, how is it that the label "out" also serves as a variable? What's going on there?
I've gotten Johannes Ahlebrand's signal generator code trimmed down to almost the simplest form that still generates a nice clean triangle in the same way as his original generator module did, but there's a programming trick in it that I just don't get.
In this code, how is it that the label "out" also serves as a variable? What's going on there?
CON
_CLKMODE = xtal1 + pll16x
_XINFREQ = 5_000_000
AUDIOPIN = 8
ADC_PIN = 9
PUB main | duty_mode
damplevel := 0
duty_mode := %00111 << 26
regCounter := duty_mode | AUDIOPIN | (ADC_PIN<<9)
noiseValue := $1000_0000
set_pindir := (1<<ADC_PIN) | (1<<AUDIOPIN)
frequency := 80 * (536_870_912 / 10_000_000) 'Generate a 80 Hz triangle wave
cognew(@triangle_wave, 0)
repeat
DAT org 0
triangle_wave
mov dira, set_pindir
mov ctra, regCounter
out mov ctrb, noiseValue
'───────────────────────────────────────────────────────────
mainLoop
sar out, damplevel
add out, dcOffset
mov frqa, out
mov frqb, frequency
absneg out, phsb
shl out, #1
sub out, dcOffset
jmp #mainLoop
'───────────────────────────────────────────────────────────
dcOffset long 1<<31
regCounter long 0-0
noiseValue long 0-0
set_pindir long 0-0
frequency long 0-0
damplevel long 0-0
{
┌──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
│ Propeller Signal Generator v1.2 (C) 2012 Johannes Ahlebrand │
├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
│ TERMS OF USE: Parallax Object Exchange License │
├──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
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}
Comments
Once the init opcode is executed, the RAM may be used as a VAR,but it does hurt the eyeballs...
Hehe, oh the freedoms of assembler ...
I guess the reason for it is, because it is possible! There is no reason for saving space this way when just a TINY bit of the cog RAM is utilized by the signal generator anyway, I could have reserved a variable instead. In Retronitus I did the same thing, but it REALLY is a tight fit, so there is a lot of "tricks" like that in there.
/Johannes
Retronitus is a work of art, by the way! It's amazing.