- From: Frank Mori Hess <fmhess_at_users.sourceforge.net>
- Date: Tue, 24 Sep 2002 18:34:43 -0500
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Tuesday 24 September 2002 05:50 pm, David Schleef wrote: > On Tue, Sep 24, 2002 at 06:10:29PM -0400, Alan Chen wrote: > > I am having a troublesome problem with comedi and/or the dio board . It > > seems that I must perform some akward operations for the board to work > > correctly. > > > > So I am trying to set all the channels (0-23) in all the subdevices > > (0-3) to either 1 or 0. It turns out that the following graph is what I > > get (source pasted below): > > > > comedi_dio_write(...,1) alone gets a random amount of 1's and 0's > > ~ (although they seem clustered) > > This sounds like a driver bug. I've suspected for a while that > there might be problems in that area, but the code does exactly > what the manual says, and there have been no complaints with > other 8255 boards. I don't have the hardware to experiment with. > As I recall my experience with the 8255 chip (or maybe it's just 8255 - compatible), when the input/output configuration of any pin is set, it can change the state of other output pins. The only way to make it work right was to set up the input/output configuration of all the pins at the beginning and then leave them alone. I also looked for bugs in the driver and found none. I suppose it could force a write to all the output pins every time the configuration is changed, although that still would leave transient glitches. - -- Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE9kPaV5vihyNWuA4URAoBqAJ9pqZm3CjYzc3Ef6g5xQkJKSDjvJQCgwMeK rTdomt3aMuvqtMy5pLVR+QQ= =DJvs -----END PGP SIGNATURE-----
Received on 2002-09-24Z22:34:43