clemon@lemsys.UUCP (Craig Lemon) (09/17/90)
I was looking at a copy of AudioMaster II (Amiga) running the other
day and noticed an option for a mouseport sampler. I would be very
interested in any specs on this type of digitizer. The Game Port already
has an ADC for "paddle" inputs right? This should make the construction
easier than any other way. If this is not the case, I'd be interested in
making an adapter to the gameport from a parrallel port type sampler.
I am looking at writing some software that I would like to use a
sampler but don't really feel like sacrificing other parallel port
activites. Actually in some cases I have no choice, the parallel port is
already used for other data aqusition purposes.
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Craig Lemon - Kitchener, Ontario. Amiga B2000/10--2400 bps--AmigaUUCP 1.03D
lemsys!clemon@xenitec.on.ca or ....!{uunet}!watmath!xenitec!lemsys!clemontell@oscar.cs.unc.edu (Stephen Tell) (09/19/90)
In article <02488.AA02488@lemsys.UUCP> clemon@lemsys.UUCP (Craig Lemon) writes: > > I was looking at a copy of AudioMaster II (Amiga) running the other >day and noticed an option for a mouseport sampler. I would be very >interested in any specs on this type of digitizer. The Game Port already >has an ADC for "paddle" inputs right? This should make the construction >easier than any other way. If this is not the case, I'd be interested in >making an adapter to the gameport from a parrallel port type sampler. I you're out of luck here. The way the analog joystick/paddle interface works isn't suitable for audio input. There's a midsize capacitor connected between the pin and ground, and the paddle or joystick is a pot wired to +5v. During the vertical blanking interval of the video, the driver software turns on a transistor to discharge the capacitor, and resets an 8-bit hardware counter. The capacitor then charges through the external resistor. When it crosses a threshold, the counter stops counting. At the next vertical interupt, software reads the counter as the joystick position and starts the whole process over. So, using some kind of electronicly-variable resistance (like a photocell or FET) you could get a sort of A-to-D, but it is limited to 60Hz sampling. This is just fine for video games; you get a new position input every video frame, but just won't do for audio. An adaptor could be constructed if you were building your own digitzer or knew exactly how the paralell port unit used the port. The mouse port pins can be taken over by your own software, giving you somthing like three bits of I/O and another bit of input only. You would use one of them for a clock and another for data and shift the data serialy. There are even serial ADC chips that people have interfaced this way. There are operating system calls to allocate these port bits for your use and read/write them; accessing the hardware directly is a big no-no on the Amiga. Followups on this to comp.sys.amiga. I can send you some sample code that twiddles these bits if you want. > Craig Lemon - Kitchener, Ontario. Amiga B2000/10--2400 bps--AmigaUUCP 1.03D > lemsys!clemon@xenitec.on.ca or ....!{uunet}!watmath!xenitec!lemsys!clemon -------------------------------------------------------------------- Steve Tell e-mail: tell@wsmail.cs.unc.edu usmail: #5L Estes Park apts CS Grad Student, UNC Chapel Hill. Carrboro NC 27510