WLDS amplitude coefficient usage?
Posted: Thu Oct 23, 2014 11:26 am
Can somebody explain how to use the amplitude coefficient (Ka) in the WLDS instruction?:
WLDS SIN0, Kf, Ka
If I want to implement a chorus and sweep sinusoidally through a delay memory, it seems important that the pointer does not go past the start or end of the delay. I've seen some documentation that says that Ka is the number of addresses on one side of the sine wave, so the peak to peak number of addresses is 2*Ka. This makes sense to me...
However, I've seen other documentation, written by Frank Thompson (presumably the same Frank who monitors this forum), which claims that:
Ka = 2*N, where N is the delay length in samples.... this seems backwards.
To make matters worse, the example code on the website for rom_rev1 calls this instruction:
WLDS SIN0, 12, 160 ;+/- 20 samples (???)
and then:
CHO RDA, SIN0, 0x06, ap1+50
Here, the 50th address of ap1 is the midpoint of the chorus wobble, but if Ka of SIN0 is 160... the pointer should certainly move past the beginning of ap1, regardless of whether Ka=N/2 or Ka=2*N.
Please help. Thanks! javascript:emoticon(':D')
WLDS SIN0, Kf, Ka
If I want to implement a chorus and sweep sinusoidally through a delay memory, it seems important that the pointer does not go past the start or end of the delay. I've seen some documentation that says that Ka is the number of addresses on one side of the sine wave, so the peak to peak number of addresses is 2*Ka. This makes sense to me...
However, I've seen other documentation, written by Frank Thompson (presumably the same Frank who monitors this forum), which claims that:
Ka = 2*N, where N is the delay length in samples.... this seems backwards.
To make matters worse, the example code on the website for rom_rev1 calls this instruction:
WLDS SIN0, 12, 160 ;+/- 20 samples (???)
and then:
CHO RDA, SIN0, 0x06, ap1+50
Here, the 50th address of ap1 is the midpoint of the chorus wobble, but if Ka of SIN0 is 160... the pointer should certainly move past the beginning of ap1, regardless of whether Ka=N/2 or Ka=2*N.
Please help. Thanks! javascript:emoticon(':D')