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View Code? Open in Web Editor NEWTouchscreen calibration library
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Touchscreen calibration library
License: Other
$Id: README,v 1.4 2004/07/21 19:12:58 dlowder Exp $ General ======= The idea of tslib is to have a core library that provides standardised services, and a set of plugins to manage the conversion and filtering as needed. The plugins for a particular touchscreen are loaded automatically by the library under the control of a static configuration file, ts.conf. ts.conf gives the library basic configuration information. Each line specifies one module, and the parameters for that module. The modules are loaded in order, with the first one processing the touchscreen data first. For example: module_raw input module variance delta=30 module dejitter delta=100 module linear These parameters are described below. With this configuration file, we end up with the following data flow through the library: raw read --> variance --> dejitter --> linear --> application module module module module You can re-order these modules as you wish, add more modules, or remove them all together. When you call ts_read(), the values you read are values that have passed through the chain of filters and scaling conversions. Another call is provided, ts_read_raw() which bypasses all the modules and reads the raw data directly from the device. There are a couple of programs in the tslib/test directory which give example usages. They are by no means exhaustive, nor probably even good examples. They are basically the programs used to test this library. Environment Variables ===================== TSLIB_TSDEVICE TS device file name. Default (non inputapi): /dev/touchscreen/ucb1x00 Default (inputapi): /dev/input/event0 TSLIB_CALIBFILE Calibration file. Default: ${sysconfdir}/pointercal TSLIB_CONFFILE Config file. Default: ${sysconfdir}/ts.conf TSLIB_PLUGINDIR Plugin directory. Default: ${datadir}/plugins TSLIB_CONSOLEDEVICE Console device. Default: /dev/tty TSLIB_FBDEVICE Framebuffer device. Default: /dev/fb0 Module Creation Notes ===================== For those creating tslib modules, it is important to note a couple things with regard to handling of the ability for a user to request more than one ts event at a time. The first thing to note is that the lower layers may send up less events than the user requested, because some events may be filtered out by intermediate layers. Next, your module should send up just as many events as the user requested in nr. If your module is one that consumes events, such as variance, then you loop on the read from the lower layers, and only send the events up when 1) you have the number of events requested by the user, or 2) one of the events from the lower layers was a pen release. Module Parameters ================= module: variance ---------------- Description: Variance filter. Tries to do it's best in order to filter out random noise coming from touchscreen ADC's. This is achieved by limiting the sample movement speed to some value (e.g. the pen is not supposed to move quicker than some threshold). This is a 'greedy' filter, e.g. it gives less samples on output than receives on input. Parameters: delta Set the squared distance in touchscreen units between previous and current pen position (e.g. (X2-X1)^2 + (Y2-Y1)^2). This defines the criteria for determining whenever two samples are 'near' or 'far' to each other. Now if the distance between previous and current sample is 'far', the sample is marked as 'potential noise'. This doesn't mean yet that it will be discarded; if the next reading will be close to it, this will be considered just a regular 'quick motion' event, and it will sneak to the next layer. Also, if the sample after the 'potential noise' is 'far' from both previously discussed samples, this is also considered a 'quick motion' event and the sample sneaks into the output stream. module: dejitter ---------------- Description: Removes jitter on the X and Y co-ordinates. This is achieved by applying a weighted smoothing filter. The latest samples have most weight; earlier samples have less weight. This allows to achieve 1:1 input->output rate. Parameters: delta Squared distance between two samples ((X2-X1)^2 + (Y2-Y1)^2) that defines the 'quick motion' threshold. If the pen moves quick, it is not feasible to smooth pen motion, besides quick motion is not precise anyway; so if quick motion is detected the module just discards the backlog and simply copies input to output. module: linear -------------- Description: Linear scaling module, primerily used for conversion of touch screen co-ordinates to screen co-ordinates. Parameters: xyswap interchange the X and Y co-ordinates -- no longer used or needed if the new linear calibration utility ts_calibrate is used.
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