TouchSense.h

00001 /* mbed Microcontroller Library
00002  * Copyright (c) 2013 Shinichiro Nakamura
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 
00017 #ifndef TOUCHSENSE_H
00018 #define TOUCHSENSE_H
00019 
00020 #include "platform.h"
00021 #include "gpio_api.h"
00022 #include "analogin_api.h"
00023 
00024 namespace mbed
00025 {
00026 
00027 /**
00028  * A capacitive touch sensor using analog input port.
00029  *
00030  * Example:
00031  * @code
00032  * #include "mbed.h"
00033  *
00034  * TouchSense tp(p18);
00035  *
00036  * int main() {
00037  *     tp.calibration();
00038  *     while(1) {
00039  *         if (tp.sense()) {
00040  *             printf("ON\r\n");
00041  *         } else {
00042  *             printf("OFF\r\n");
00043  *         }
00044  *         wait(0.1);
00045  *     }
00046  * }
00047  * @endcode
00048  */
00049 class TouchSense
00050 {
00051 
00052 public:
00053     /**
00054      * Create a TouchSense connected to the specified pin
00055      *
00056      * @param pin TouchSense pin to connect to
00057      * @param thr Threshold (1 to 20)
00058      */
00059     TouchSense(PinName pin, int thr = 10) : mypin(pin), calval(0) {
00060         for (int i = 0; i < DATA_COUNT; i++) {
00061             data[i] = 0;
00062         }
00063         if (thr < THRMIN) {
00064             thr = THRMIN;
00065         }
00066         if (thr > THRMAX) {
00067             thr = THRMAX;
00068         }
00069         threshold = thr;    
00070         execute();
00071     }
00072 
00073     void calibration() {
00074         uint32_t r = 0;
00075         for (int i = 0; i < DATA_COUNT; i++) {
00076             r += execute();
00077             wait_us(100);
00078         }
00079         r = r / DATA_COUNT;
00080         calval = r;
00081     }
00082 
00083     bool sense() {
00084         data[index] = execute();
00085         index = (index + 1) % DATA_COUNT;
00086         uint32_t r = 0;
00087         for (int i = 0; i < DATA_COUNT; i++) {
00088             r += data[i];
00089         }
00090         r = r / DATA_COUNT;
00091         return (calval * threshold) < r;
00092     }
00093 
00094 private:
00095 
00096     uint16_t execute() {
00097         uint16_t r;
00098         analogin_init(&adc, mypin);
00099         r = analogin_read_u16(&adc) >> 4;
00100         gpio_init_out(&gpio, mypin);
00101         gpio_write(&gpio, 1);
00102         return r;
00103     }
00104 
00105 protected:
00106     PinName mypin;
00107     uint16_t calval;
00108     gpio_t gpio;
00109     analogin_t adc;
00110     static const int DATA_COUNT = 8;
00111     uint32_t data[DATA_COUNT];
00112     int index;
00113     int threshold;
00114     static const int THRMIN = 1;
00115     static const int THRMAX = 20;
00116 };
00117 
00118 } // namespace mbed
00119 
00120 #endif