A device driver for the Freescale MPR121 capactive touch IC. Not optimized for any particular system, just a starting point to get the chip up in running in no time. Changes to registers init() method will tailor the library for end system use.

Dependents:   Seeed_Grove_I2C_Touch_Example MPR121_HelloWorld mbed_petbottle_holder_shikake test_DEV-10508 ... more

Datasheet:

http://cache.freescale.com/files/sensors/doc/data_sheet/MPR121.pdf

Information

Must add pull-ups to the I2C bus!!

Revision:
5:3934358ec2b7
Parent:
3:828260f21de6
Child:
6:b6bb38744edd
diff -r 828260f21de6 -r 3934358ec2b7 MPR121.cpp
--- a/MPR121.cpp	Tue Aug 27 21:39:33 2013 +0000
+++ b/MPR121.cpp	Fri Aug 15 23:00:13 2014 +0000
@@ -24,13 +24,22 @@
 #include "mbed_debug.h"
 
 #define DEBUG 1
-    
+
 MPR121::MPR121(I2C &i2c, InterruptIn &pin, MPR121_ADDR i2c_addr)
 {
     _i2c = &i2c;
     _irq = &pin;
     _i2c_addr = (i2c_addr << 1);
-    
+
+    return;
+}
+
+MPR121::MPR121(I2C &i2c, MPR121_ADDR i2c_addr)
+{
+    _i2c = &i2c;
+    _irq = NULL;
+    _i2c_addr = (i2c_addr << 1);
+
     return;
 }
 
@@ -39,11 +48,13 @@
     // set the i2c speed
     _i2c->frequency(400000);
     // irq is open-collector and active-low
-    _irq->mode(PullUp);
-    
+    if(_irq != NULL) {
+        _irq->mode(PullUp);
+    }
+
     // setup and registers - start with POR values (must be in stop mode)
     MPR121::writeRegister(SRST, 0x63); //REG 0x80
-    
+
     // Baseline Filtering Control Register (changes response sensitivity)
     // http://cache.freescale.com/files/sensors/doc/app_note/AN3891.pdf
     MPR121::writeRegister(MHDR, 0x1);  //REG 0x2B
@@ -54,25 +65,23 @@
     MPR121::writeRegister(NHDF, 0x1);  //REG 0x30
     MPR121::writeRegister(NCLF, 0xFF); //REG 0x31
     MPR121::writeRegister(FDLF, 0x2);  //REG 0x32
-    
+
     // Touch / Release Threshold
     // cache.freescale.com/files/sensors/doc/app_note/AN3892.pdf
-    for(int i=0; i<(12*2); i+=2) // touch
-    {
+    for(int i=0; i<(12*2); i+=2) { // touch
         MPR121::writeRegister(static_cast<MPR121_REGISTER>(E0TTH+i), 0x20); //REG 0x41...0x58 odd
     }
-    for(int i=0; i<(12*2); i+=2) // release
-    {
+    for(int i=0; i<(12*2); i+=2) { // release
         MPR121::writeRegister(static_cast<MPR121_REGISTER>(E0RTH+i), 0x10); //REG 0x41...0x58 even
     }
-    
+
     // Debounce Register DR=b6...4, DT=b2...0
     MPR121::writeRegister(DT_DR, 0x11); //REG 0x5B
-    
+
     // Filter and Global CDC CDT Configuration (sample time, charge current)
     MPR121::writeRegister(CDC_CONFIG, 0x10); //REG 0x5C default 10
     MPR121::writeRegister(CDT_CONFIG, 0x20); //REG 0x5D default 24
-    
+
     // Auto-Configuration Registers
     // http://cache.freescale.com/files/sensors/doc/app_note/AN3889.pdf
     MPR121::writeRegister(AUTO_CFG0, 0x33); // REG 0x7B
@@ -81,10 +90,10 @@
     MPR121::writeRegister(LSL, 0x83);       // REG 0x7E((3.3-.07)/3.3) * 256 * 0.65f
     MPR121::writeRegister(TL,  0xb5);       // REG 0x7F((3.3-.07)/3.3) * 256 * 0.9f
     // 255 > USL > TL > LSL > 0
-    
+
     // Electrode Configuration Register - enable all 12 and start
     MPR121::writeRegister(ECR, 0x8f);
-    
+
     return;
 }
 
@@ -96,8 +105,10 @@
     //  lower current consumption mode
     MPR121::writeRegister(ECR, 0x8f);
     // and attach the interrupt handler
-    _irq->fall(this, &MPR121::handler);
-    
+    if(_irq != NULL) {
+        _irq->fall(this, &MPR121::handler);
+    }
+
     return;
 }
 
@@ -111,7 +122,7 @@
     MPR121::writeRegister(ECR, 0x0);
     MPR121::writeRegister(AUTO_CFG0, 0x0); // REG 0x7B
     MPR121::writeRegister(AUTO_CFG1, 0x0); // REG 0x7C
-    
+
     return;
 }
 
@@ -122,6 +133,9 @@
 
 uint16_t MPR121::buttonPressed(void)
 {
+    if(_irq == NULL) {
+        handler();
+    }
     _button_has_changed = 0;
     return _button;
 }
@@ -129,13 +143,24 @@
 void MPR121::registerDump(Serial &obj) const
 {
     uint8_t reg_val = 0;
-    
-    for(int i=0; i<0x80; i++)
-    {
+
+    for(int i=0; i<0x80; i++) {
         reg_val = MPR121::readRegister(static_cast<MPR121_REGISTER>(i));
         obj.printf("Reg 0x%02x: 0x%02x \n", i, reg_val);
     }
-    
+
+    return;
+}
+
+void MPR121::registerDump(void) const
+{
+    uint8_t reg_val = 0;
+
+    for(int i=0; i<0x80; i++) {
+        reg_val = MPR121::readRegister(static_cast<MPR121_REGISTER>(i));
+        printf("Reg 0x%02x: 0x%02x \n", i, reg_val);
+    }
+
     return;
 }
 
@@ -148,19 +173,18 @@
     // 2 and 3
     oor_val  = MPR121::readRegister(ELE0_7_OOR_STAT);
     oor_val |= MPR121::readRegister(ELE8_11_OOR_STAT) << 8;
-    
+
     // debugging stuff and errors - if OOR fails someone was touching the pad during auto-config
     //  Just reboot until they're not doing this
-    if((0 != oor_val) && DEBUG)
-    {
+    if((0 != oor_val) && DEBUG) {
         debug("MPR121 OOR failure - 0x%04x\n", oor_val);
         wait(0.1f);
         NVIC_SystemReset();
     }
-   
+
     _button = reg_val;
     _button_has_changed = 1;
-    
+
     return;
 }
 
@@ -168,14 +192,13 @@
 {
     char buf[2] = {reg, data};
     uint8_t result = 0;
-    
+
     result = _i2c->write(_i2c_addr, buf, 2);
-    
-    if(result && DEBUG)
-    {
+
+    if(result && DEBUG) {
         debug("I2c write failed\n");
     }
-    
+
     return;
 }
 
@@ -183,14 +206,13 @@
 {
     char buf[1] = {reg}, data = 0;
     uint8_t result = 1;
-    
+
     result &= _i2c->write(_i2c_addr, buf, 1, true);
-    result &= _i2c->read(_i2c_addr, &data, 1); 
-    
-    if(result && DEBUG)
-    {
+    result &= _i2c->read(_i2c_addr, &data, 1);
+
+    if(result && DEBUG) {
         debug("I2c read failed\n");
     }
-    
+
     return data;
 }