.TH TOUCH 3.SH NAMEtouch \- touch screen.SH SYNOPSIS.EXbind -a '#T' /dev /dev/touchcal/dev/touchctl/dev/touchstat/dev/touch.EE.SH DESCRIPTIONThe touch screen driverserves a one-level directory giving access to a touch panel.The driver attempts to compensatefor the warped nature of the panels we have used:amongst other things,it repeatedly samples the panel to obtain a stable reading,and applies a transformation to the.RI ( "x, y" )coordinates obtained to account for the peculiar distortions of individual panels.A panel should be calibrated by.IR touchcal (8)before use..PPThere are two variants of the driver.One drives aDynaPro touch panelon a York Electronics Centre BRD/98/024 interface (Version A)accessed via the Motorola MPC8xx SPI interface.The other drives a different pressure-sensitive touch panel on a webphone reference design..PPThe driver initialisation starts a kernel process to read samples from thetouch screen and provide them to the system through the interface usedfor mouse events.The events generated mark`mouse button' 1 as down as long as the panel is touched and up otherwise.Other `mouse buttons' are always up.This is adequate for many applications (but not.IR acme (1))..PPThe data file.B touchis read-only.Each read samples the touch paneland returns two decimal numbers, separated by a space,giving the.I xand.I ycoordinates read.The values are both -1 if a consistent reading could not be made.This file is used only for debugging; the window system should not be running..PPThe control file.B touchctlaccepts commands to set driver parameters:.TF "X a b c".PD.TP.BI X " a b c"(MPC8xx only) Set the parameters for a transformation of the X-coordinates received from thepanel:.RS.IP.IR "x' = a*x+b*y+c".PPThe values are fixed-point: 1.0 is represented by 2\u\s-216\s0\d..RE.TP.BI Y " d e f"(MPC8xx only) Set the parameters for a similar transformation of Y-coordinates:.RS.IP.IR "y' = d*x+e*y+f".RE.TP.BI s nSample every.I nmilliseconds..TP.BI c "p sx sy"(SA1100) Wait for the screen to be touched and sample parameters for point.IR p ,0\(<=\fIp\fP\(<=3,corresponding to one of the four corners of the screen.Save the sample parameters for calibration..TP.B C(SA1100) Compute calibration parameters based on previously stored samples..TP.BI r nSets delay between touch reads..TP.BI R nAverage.RI 2 ^nreadings each sample..TP.BI f nSet the filter level (-1024 \(<=\fIn\fP\(<=1024)..TP.BI e "x y"Set error term for.I xand.IR y ;normally calculated by.BR C ..TP.BI t "p r"Set pressure threshold for press and release.PPReads of.B touchctlreturn all current parameters in the same form as the commands(allowing settings to be read from the file and later restored by simply writing them back)..PPThe read-only file.B touchstatcontains four decimal values separated by spaces or newlines:the number of raw samples, the number of valid samples,microseconds waiting for samples, and microseconds spent processing samples..PPThe SA1100 driverprovides a file.B /dev/touchcalthat holds the calibration results as a set ofdecimal numbers for each of the four sample points, one set per line.The results can be saved and written back to restore the same calibration..SH SOURCE.B /os/mpc/devtouch.c.br.B /os/sa1100/devtouch.c.SH SEE ALSO.IR touchcal (8)