- From: Frank Mori Hess <fmhess_at_users.sourceforge.net>
- Date: Tue, 2 Dec 2003 21:45:19 -0500
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Sunday 30 November 2003 03:49 am, Bob Estes wrote: > I'm quite confused about the calibration stuff too. > > > > > is done. But what is with the other subdevices? "comedi_calibrate > > --help" and "man comedi_calibrate" didn't help. Do I need to calibrate > > every device and subdevice? Or is something wrong with comedi? > > > > Greetings > > > > Mirko I've updated the docs for comedi_calibrate and comedi_apply_calibration() a bit. Here is the updated part of the comedi_apply_calibration() description which may be helpful: Description: This function sets the calibration of the specified subdevice so that it is in proper calibration when using the specified channel, range and aref. It does so by performing writes to the appropriate channels of the board's calibration subdevice(s). Depending on the hardware, the calibration settings used may or may not depend on the channel, range, or aref. Furthermore, the calibrations for different channels, ranges, or arefs may not be independent. For example, some boards cannot have their analog inputs calibrated for multiple input ranges simultaneously. Applying a calibration for range 1 may blow away a previously applied calibration for range 0. Applying a calibration for an analog input channel may cause the calibration to be applied to all the other channels as well. Your only guarantee is that calls to comedi_apply_calibration() on different subdevices will not interfere with each other. In practice, their are some rules of thumb on how calibrations behave. No calibrations depend on the aref. A multiplexed analog input will have calibration settings that do not depend on the channel, and applying a setting to one channel will affect all channels. Analog outputs, and analog inputs with independent a/d converters for each channel, will have calibrations settings which depend on the channel, and the settings for each channel will be independent of the other channels. If you wish to investigate exactly what comedi_apply_calibration() is doing, you can perform reads on your board's calibration subdevice(s) to see which calibration channels are being changed. You can also try to decipher the calibration file directly (it's a text file). - -- Frank -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (GNU/Linux) Comment: For info see http://www.gnupg.org iD8DBQE/zU4/5vihyNWuA4URAoAYAKCrC79xXAfqsH8Zn1kUvAG/CNG3MACePBve nTnzIRL+B/O6aBmxcwKmi98= =ovZH -----END PGP SIGNATURE-----
Received on 2003-12-03Z02:45:19