Erik - / SoftI2C

A software I2C interface which is a drop-in replacement for the regular mbed I2C interface in case you run out of I2C ports

Dependents:   Luminocity laser-tag

This is a first version. Doesn't mean more versions will come, mainly means it may be a bit buggy. If it does not work for you: first try exactly the same code with the regular hardware I2C. If that does work, well then I made an error somewhere :D. You can send me a message if you can't figure it out, although without your hardware it generally is hard for me to reproduce.

While basic I2C should work, advanced things like clock stretching and multi-master I2C busses are not supported.

If you find an error and solve it: Send a pull request and I generally will accept it :).

SoftI2C.h

Committer:
Sissors
Date:
2016-11-28
Revision:
1:05473196d133
Parent:
0:fee70b6fe0e9

File content as of revision 1:05473196d133:

#include "mbed.h"

#ifndef SOFTI2C_H
#define SOFTI2C_H

/**
* A software I2C class in case you run out of hardware I2C pins or cannot use
* those for another reason.
* 
* The class is a drop-in replacement of the classic mbed I2C class: include 
* this file in your program, replace I2C with SoftI2C when creating the object
* and it should work properly without other modifications.
*/
class SoftI2C {
    public:
    /**
    * Create an software I2C Master interface, connected to the specified pins
    *
    * @param sda I2C data pin 
    * @param scl I2C clock pin
    */
    SoftI2C(PinName sda, PinName scl);
    
    /**
    * Set the frequency of the I2C interface. 
    *
    * Note that the delay of the DigitalInOuts is not compensated: the real
    * frequency will be lower than the one set. However since I2C is a
    * synchronous protocol this shouldn't affect functionality
    *
    * @param hz The bus frequency in hertz 
    */ 
    void frequency(int hz);
    
    /**
    * Read from an I2C slave. 
    * 
    * Performs a complete read transaction. The bottom bit of the address is forced to 1 to indicate a read.
    *
    * @param address 8-bit I2C slave address [ addr | 1 ] 
    * @param Pointer to the byte-array data to read to 
    * @param length Number of bytes to read
    * @param repeated Repeated start, true - do not send stop at end
    * @return 0 on success (ack), non-0 on failure (nack) 
    */
    int read(int address, char *data, int length, bool repeated=false);  
    
    /**
    * Read a single byte from the I2C bus
    *
    * @param ack indicates if the byte is to be acknowledged (1 = acknowledge)
    * @return the byte read
    */
    int read(int ack);
    
    /**
    * Write to an I2C slave. 
    * 
    * Performs a complete write transaction. The bottom bit of the address is forced to 0 to indicate a write.
    *
    * @param address 8-bit I2C slave address [ addr | 0 ] 
    * @param Pointer to the byte-array data to send 
    * @param length Number of bytes to send
    * @param repeated Repeated start, true - do not send stop at end
    * @return 0 on success (ack), non-0 on failure (nack) 
    */
    int write(int address, const char *data, int length, bool repeated=false);  
    
    /**
    * Write single byte out on the I2C bus
    *
    * @param data data to write on the bus
    * @return '1' if an ACK is received, '0' otherwise
    */
    int write(int data);
    
    /**
    * Create a (re-)start condition on the I2C bus
    */
    void start(void);
    
    /**
    * Create a stop condition on the I2C bus
    */
    void stop(void);
    
    protected:
    DigitalInOut _sda;
    DigitalInOut _scl;
    int delay_us;
    bool active;
};


#endif