SoftwareI2C.h

00001 /* 
00002  * mbed Library to use a software master i2c interface on any GPIO pins
00003  * Copyright (c) 2012 Christopher Pepper
00004  * Released under the MIT License: http://mbed.org/license/mit
00005  */
00006 
00007 #ifndef _SOFTWARE_I2C_H_
00008 #define _SOFTWARE_I2C_H_
00009 
00010 #include "mbed.h"
00011 
00012 /**
00013   * @brief SoftwareI2C class
00014   */
00015 
00016 class SoftwareI2C {
00017 public:
00018     SoftwareI2C(PinName sda, PinName scl);
00019     ~SoftwareI2C();
00020 
00021     void read(uint8_t device_address, uint8_t* data, uint8_t data_bytes);
00022     void write(uint8_t device_address, uint8_t* data,  uint8_t data_bytes);
00023     void write(uint8_t device_address, uint8_t byte);
00024     void randomRead(uint8_t device_address, uint8_t start_address, uint8_t* data, uint8_t data_bytes);
00025     void randomWrite(uint8_t device_address, uint8_t start_address, uint8_t* data, uint8_t data_bytes);
00026     void randomWrite(uint8_t device_address, uint8_t start_address, uint8_t byte);
00027     
00028     uint8_t read8(uint8_t device_address, uint8_t start_address);
00029     uint16_t read16(uint8_t device_address, uint8_t start_address);
00030     uint32_t read24(uint8_t device_address, uint8_t start_address);
00031     uint32_t read32(uint8_t device_address, uint8_t start_address);
00032     
00033     void setDeviceAddress(uint8_t address){
00034         _device_address = address;
00035     }
00036     
00037     void setFrequency(uint32_t frequency){
00038         _frequency_delay = 1000000 / frequency;
00039     }
00040 
00041     inline void initialise() {
00042         _scl.output();
00043         _sda.output();
00044         
00045         _sda = 1;
00046         _scl = 0;
00047         warte(_frequency_delay);
00048 
00049         for ( int n = 0; n <= 3; ++n ) {
00050             stop();
00051         }
00052     }
00053 
00054 private:
00055     void warte(int zeit)
00056     {
00057      for (int i=0;i<zeit*5;i++)
00058      {
00059       asm("nop\n\t");   
00060      }   
00061     }
00062     inline void start() {
00063         _sda.output();
00064         warte(_frequency_delay);
00065         _scl = 1;
00066         _sda = 1;
00067         warte(_frequency_delay);
00068         _sda = 0;
00069         warte(_frequency_delay);
00070         _scl = 0;
00071         warte(_frequency_delay);
00072     }
00073 
00074     inline void stop() {
00075         _sda.output();
00076         warte(_frequency_delay);
00077         _sda = 0;
00078         warte(_frequency_delay);
00079         _scl = 1;
00080         warte(_frequency_delay);
00081         _sda = 1;
00082     }
00083 
00084     inline void putByte(uint8_t byte) {
00085         _sda.output();
00086         for ( int n = 8; n > 0; --n) {
00087             warte(_frequency_delay);
00088             _sda = byte & (1 << (n-1));
00089             _scl = 1;
00090             warte(_frequency_delay);
00091             _scl = 0;
00092         }
00093         _sda = 1;
00094     }
00095 
00096     inline uint8_t getByte() {
00097         uint8_t byte = 0;
00098 
00099         _sda.input();          //release the data line
00100         _sda.mode(OpenDrain);
00101         
00102         warte(_frequency_delay);
00103 
00104         for ( int n = 8; n > 0; --n ) {
00105             _scl=1;            //set clock high
00106             warte(_frequency_delay);
00107             byte |= _sda << (n-1); //read the bit
00108             warte(_frequency_delay);
00109             _scl=0;            //set clock low
00110             warte(_frequency_delay);
00111         }
00112 
00113         _sda.output();         //take data line back
00114 
00115         return byte;
00116     }
00117 
00118     inline void giveAck() {
00119         _sda.output();
00120         warte(_frequency_delay);
00121         _sda = 0;
00122         _scl = 1;
00123         warte(_frequency_delay);
00124         _scl = 0;
00125         _sda = 1;
00126 
00127     }
00128 
00129     inline bool getAck() {
00130         _sda.output();
00131         _sda = 1;
00132         _scl = 1;
00133         _sda.input();
00134         _sda.mode(OpenDrain);
00135         warte(_frequency_delay);
00136         _scl = 0;
00137 
00138         if(_sda != 0){return false;}
00139 
00140         warte(_frequency_delay);
00141         return true;
00142     }
00143 
00144     DigitalInOut _sda;
00145     DigitalInOut _scl;
00146     
00147     uint8_t _device_address;
00148     uint32_t _frequency_delay;
00149 };
00150 
00151 #endif