From a03c337cdb9fa2e7c1a8302447a70644588bc91c Mon Sep 17 00:00:00 2001 From: Frank Mori Hess Date: Wed, 3 Dec 2003 02:43:22 +0000 Subject: [PATCH] trying to improve calibration docs --- doc/funcref | 35 +++++++++++++++++++++++++++++++++-- 1 file changed, 33 insertions(+), 2 deletions(-) diff --git a/doc/funcref b/doc/funcref index 0d935f3..8abf806 100644 --- a/doc/funcref +++ b/doc/funcref @@ -846,9 +846,40 @@ Status: alpha 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. Depending on the hardware, the + 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. The file_path parameter can be used + 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 analog input channel 0 may cause the same + calibration to be applied to all the + other analog input 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 for one + channel will affect + all channels equally. Analog outputs, and analog inputs + with independent a/d converters for each input channel, will have + calibrations settings which do 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 to see which calibration channels it is changing. + You can also try to decipher the calibration file directly (it's a + text file). + + The file_path parameter can be used to specify the file which contains the calibration information. If file_path is NULL, then comedilib will use a default -- 2.26.2