SoftI2C.h

00001 #include "mbed.h"
00002 
00003 #ifndef SOFTI2C_H
00004 #define SOFTI2C_H
00005 
00006 /**
00007 * A software I2C class in case you run out of hardware I2C pins or cannot use
00008 * those for another reason.
00009 * 
00010 * The class is a drop-in replacement of the classic mbed I2C class: include 
00011 * this file in your program, replace I2C with SoftI2C when creating the object
00012 * and it should work properly without other modifications.
00013 */
00014 class SoftI2C {
00015     public:
00016     /**
00017     * Create an software I2C Master interface, connected to the specified pins
00018     *
00019     * @param sda I2C data pin 
00020     * @param scl I2C clock pin
00021     */
00022     SoftI2C(PinName sda, PinName scl);
00023     
00024     /**
00025     * Set the frequency of the I2C interface. 
00026     *
00027     * Note that the delay of the DigitalInOuts is not compensated: the real
00028     * frequency will be lower than the one set. However since I2C is a
00029     * synchronous protocol this shouldn't affect functionality
00030     *
00031     * @param hz The bus frequency in hertz 
00032     */ 
00033     void frequency(int hz);
00034     
00035     /**
00036     * Read from an I2C slave. 
00037     * 
00038     * Performs a complete read transaction. The bottom bit of the address is forced to 1 to indicate a read.
00039     *
00040     * @param address 8-bit I2C slave address [ addr | 1 ] 
00041     * @param Pointer to the byte-array data to read to 
00042     * @param length Number of bytes to read
00043     * @param repeated Repeated start, true - do not send stop at end
00044     * @return 0 on success (ack), non-0 on failure (nack) 
00045     */
00046     int read(int address, char *data, int length, bool repeated=false);  
00047     
00048     /**
00049     * Read a single byte from the I2C bus
00050     *
00051     * @param ack indicates if the byte is to be acknowledged (1 = acknowledge)
00052     * @return the byte read
00053     */
00054     int read(int ack);
00055     
00056     /**
00057     * Write to an I2C slave. 
00058     * 
00059     * Performs a complete write transaction. The bottom bit of the address is forced to 0 to indicate a write.
00060     *
00061     * @param address 8-bit I2C slave address [ addr | 0 ] 
00062     * @param Pointer to the byte-array data to send 
00063     * @param length Number of bytes to send
00064     * @param repeated Repeated start, true - do not send stop at end
00065     * @return 0 on success (ack), non-0 on failure (nack) 
00066     */
00067     int write(int address, const char *data, int length, bool repeated=false);  
00068     
00069     /**
00070     * Write single byte out on the I2C bus
00071     *
00072     * @param data data to write on the bus
00073     * @return '1' if an ACK is received, '0' otherwise
00074     */
00075     int write(int data);
00076     
00077     /**
00078     * Create a (re-)start condition on the I2C bus
00079     */
00080     void start(void);
00081     
00082     /**
00083     * Create a stop condition on the I2C bus
00084     */
00085     void stop(void);
00086     
00087     protected:
00088     DigitalInOut _sda;
00089     DigitalInOut _scl;
00090     int delay_us;
00091     bool active;
00092 };
00093 
00094 
00095 #endif