MPR121.cpp

00001 /**
00002  * @file    MPR121.cpp
00003  * @brief   Device driver - MPR121 capactiive touch IC
00004  * @author  sam grove
00005  * @version 1.0
00006  * @see     http://cache.freescale.com/files/sensors/doc/data_sheet/MPR121.pdf
00007  *
00008  * Copyright (c) 2013
00009  *
00010  * Licensed under the Apache License, Version 2.0 (the "License");
00011  * you may not use this file except in compliance with the License.
00012  * You may obtain a copy of the License at
00013  *
00014  *     http://www.apache.org/licenses/LICENSE-2.0
00015  *
00016  * Unless required by applicable law or agreed to in writing, software
00017  * distributed under the License is distributed on an "AS IS" BASIS,
00018  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00019  * See the License for the specific language governing permissions and
00020  * limitations under the License.
00021  */
00022 
00023 #include "MPR121.h"
00024 #include "mbed_debug.h"
00025 
00026 #define DEBUG 1
00027     
00028 MPR121::MPR121(I2C &i2c, InterruptIn &pin, MPR121_ADDR i2c_addr)
00029 {
00030     _i2c = &i2c;
00031     _irq = &pin;
00032     _i2c_addr = (i2c_addr << 1);
00033     
00034     return;
00035 }
00036 
00037 void MPR121::init(void)
00038 {
00039     // set the i2c speed
00040     _i2c->frequency(400000);
00041     // irq is open-collector and active-low
00042     _irq->mode(PullUp);
00043     
00044     // setup and registers - start with POR values (must be in stop mode)
00045     MPR121::writeRegister(SRST, 0x63); //REG 0x80
00046     
00047     // Baseline Filtering Control Register (changes response sensitivity)
00048     // http://cache.freescale.com/files/sensors/doc/app_note/AN3891.pdf
00049     MPR121::writeRegister(MHDR, 0x1);  //REG 0x2B
00050     MPR121::writeRegister(NHDR, 0x1);  //REG 0x2C
00051     MPR121::writeRegister(NCLR, 0x0);  //REG 0x2D
00052     MPR121::writeRegister(FDLR, 0x0);  //REG 0x2E
00053     MPR121::writeRegister(MHDF, 0x1);  //REG 0x2F
00054     MPR121::writeRegister(NHDF, 0x1);  //REG 0x30
00055     MPR121::writeRegister(NCLF, 0xFF); //REG 0x31
00056     MPR121::writeRegister(FDLF, 0x2);  //REG 0x32
00057     
00058     // Touch / Release Threshold
00059     // cache.freescale.com/files/sensors/doc/app_note/AN3892.pdf
00060     for(int i=0; i<(12*2); i+=2) // touch
00061     {
00062         MPR121::writeRegister(static_cast<MPR121_REGISTER>(E0TTH+i), 0x20); //REG 0x41...0x58 odd
00063     }
00064     for(int i=0; i<(12*2); i+=2) // release
00065     {
00066         MPR121::writeRegister(static_cast<MPR121_REGISTER>(E0RTH+i), 0x10); //REG 0x41...0x58 even
00067     }
00068     
00069     // Debounce Register DR=b6...4, DT=b2...0
00070     MPR121::writeRegister(DT_DR, 0x11); //REG 0x5B
00071     
00072     // Filter and Global CDC CDT Configuration (sample time, charge current)
00073     MPR121::writeRegister(CDC_CONFIG, 0x10); //REG 0x5C default 10
00074     MPR121::writeRegister(CDT_CONFIG, 0x20); //REG 0x5D default 24
00075     
00076     // Auto-Configuration Registers
00077     // http://cache.freescale.com/files/sensors/doc/app_note/AN3889.pdf
00078     MPR121::writeRegister(AUTO_CFG0, 0x33); // REG 0x7B
00079     MPR121::writeRegister(AUTO_CFG1, 0x07); // REG 0x7C
00080     MPR121::writeRegister(USL, 0xc9);       // REG 0x7D((3.3-.07)/3.3) * 256
00081     MPR121::writeRegister(LSL, 0x83);       // REG 0x7E((3.3-.07)/3.3) * 256 * 0.65f
00082     MPR121::writeRegister(TL,  0xb5);       // REG 0x7F((3.3-.07)/3.3) * 256 * 0.9f
00083     // 255 > USL > TL > LSL > 0
00084     
00085     // Electrode Configuration Register - enable all 12 and start
00086     MPR121::writeRegister(ECR, 0x8f);
00087     
00088     return;
00089 }
00090 
00091 void MPR121::enable(void)
00092 {
00093     _button = 0;
00094     _button_has_changed = 0;
00095     // enable the 12 electrodes - allow disable to put device into
00096     //  lower current consumption mode
00097     MPR121::writeRegister(ECR, 0x8f);
00098     // and attach the interrupt handler
00099     _irq->fall(this, &MPR121::handler);
00100     
00101     return;
00102 }
00103 
00104 void MPR121::disable(void)
00105 {
00106     // detach the interrupt handler
00107     _irq->fall(NULL);
00108     _button = 0;
00109     _button_has_changed = 0;
00110     //  put the device in low current consumption mode - dont re-init registers
00111     MPR121::writeRegister(ECR, 0x0);
00112     MPR121::writeRegister(AUTO_CFG0, 0x0); // REG 0x7B
00113     MPR121::writeRegister(AUTO_CFG1, 0x0); // REG 0x7C
00114     
00115     return;
00116 }
00117 
00118 uint32_t MPR121::isPressed(void)
00119 {
00120     return _button_has_changed;
00121 }
00122 
00123 uint16_t MPR121::buttonPressed(void)
00124 {
00125     _button_has_changed = 0;
00126     return _button;
00127 }
00128 
00129 void MPR121::registerDump(Serial &obj) const
00130 {
00131     uint8_t reg_val = 0;
00132     
00133     for(int i=0; i<0x80; i++)
00134     {
00135         reg_val = MPR121::readRegister(static_cast<MPR121_REGISTER>(i));
00136         obj.printf("Reg 0x%02x: 0x%02x \n", i, reg_val);
00137     }
00138     
00139     return;
00140 }
00141 
00142 void MPR121::handler(void)
00143 {
00144     uint16_t reg_val = 0, oor_val = 0;
00145     // read register 0 and 1
00146     reg_val  = MPR121::readRegister(ELE0_7_STAT);
00147     reg_val |= MPR121::readRegister(ELE8_11_STAT) << 8;
00148     // 2 and 3
00149     oor_val  = MPR121::readRegister(ELE0_7_OOR_STAT);
00150     oor_val |= MPR121::readRegister(ELE8_11_OOR_STAT) << 8;
00151     
00152     // debugging stuff and errors - if OOR fails someone was touching the pad during auto-config
00153     //  Just reboot until they're not doing this
00154     if((0 != oor_val) && DEBUG)
00155     {
00156         debug("MPR121 OOR failure - 0x%04x\n", oor_val);
00157         wait(0.1f);
00158         NVIC_SystemReset();
00159     }
00160    
00161     _button = reg_val;
00162     _button_has_changed = 1;
00163     
00164     return;
00165 }
00166 
00167 void MPR121::writeRegister(MPR121_REGISTER const reg, uint8_t const data) const
00168 {
00169     char buf[2] = {reg, data};
00170     uint8_t result = 0;
00171     
00172     result = _i2c->write(_i2c_addr, buf, 2);
00173     
00174     if(result && DEBUG)
00175     {
00176         debug("I2c write failed\n");
00177     }
00178     
00179     return;
00180 }
00181 
00182 uint8_t MPR121::readRegister(MPR121_REGISTER const reg) const
00183 {
00184     char buf[1] = {reg}, data = 0;
00185     uint8_t result = 1;
00186     
00187     result &= _i2c->write(_i2c_addr, buf, 1, true);
00188     result &= _i2c->read(_i2c_addr, &data, 1); 
00189     
00190     if(result && DEBUG)
00191     {
00192         debug("I2c read failed\n");
00193     }
00194     
00195     return data;
00196 }