i2c.hpp

00001 /**
00002  * Copyright (c) 2010 Roy van Dam <roy@negative-black.org>
00003  * All rights reserved.
00004  *
00005  * Redistribution and use in source and binary forms, with or without
00006  * modification, are permitted provided that the following conditions
00007  * are met:
00008  * 1. Redistributions of source code must retain the above copyright
00009  *    notice, this list of conditions and the following disclaimer.
00010  * 2. Redistributions in binary form must reproduce the above copyright
00011  *    notice, this list of conditions and the following disclaimer in the
00012  *    documentation and/or other materials provided with the distribution.
00013  *
00014  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
00015  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
00016  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
00017  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
00018  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
00019  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
00020  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
00021  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
00022  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
00023  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
00024  * SUCH DAMAGE.
00025  */
00026 
00027 #ifndef _I2C_HPP_
00028 #define _I2C_HPP_
00029 
00030 #include "mbed.h"
00031 
00032 namespace SHTx {
00033     /**
00034      * Class: I2C
00035      *  Humidity and Temperature Sensor - SHT15
00036      *  I2C Bit-bang master driver.
00037      */
00038     class I2C {
00039     private:
00040         DigitalInOut scl_pin;
00041         DigitalInOut sda_pin;
00042     
00043         uint32_t frequency;
00044     
00045     public:    
00046         /**
00047          * Constructor: SHTx::I2C
00048            *  Create an I2C Master interface, connected to the specified pins.
00049          *  Bit-bang I2C driver to get around the lousy I2C implementation in the
00050          *  SHTx interface... 
00051          *
00052          * Variables:
00053          *  sda - I2C data line pin
00054          *  scl - I2C clock line pin
00055          */
00056         I2C(PinName sda, PinName scl);
00057     
00058         /**
00059          * Function: setFrequency
00060          *  Set the frequency of the SHTx::I2C interface
00061          *
00062          * Variables:
00063          *  hz - The bus frequency in hertz
00064          */
00065         void setFrequency(uint32_t hz);
00066 
00067         /**
00068          * Function: start
00069          *  Issue start condition on the SHTx::I2C bus
00070          */
00071         void start(void);
00072     
00073         /**
00074          * Function: stop
00075          *  Issue stop condition on the SHTx::I2C bus
00076          */
00077         void stop(void);
00078     
00079         /**
00080          * Function: wait
00081          *  Wait for SHT15 to complete measurement.
00082          *  Max timeout 500ms.
00083          *
00084          * Variables:
00085          *  returns - true if an ACK was received, false otherwise
00086          */
00087         bool wait(void);
00088 
00089         /**
00090          * Function: reset
00091          *  If communication with the device is lost
00092          *  the command will reset the serial interface
00093          */
00094         void reset(void);
00095     
00096         /**
00097          * Function: write
00098          *  Write single byte out on the SHTx::I2C bus
00099          *
00100          * Variables:
00101          *  data     - data to write out on bus
00102          *  returns - true if an ACK was received, false otherwise
00103          */
00104         bool write(uint8_t data);
00105     
00106         /**
00107          * Function: write
00108          *  Read single byte form the I2C bus
00109          *
00110          * Variables:
00111          *  ack     - indicates if the byte is to be acknowledged
00112          *  returns - the read byte
00113          */
00114         uint8_t read(bool ack);
00115 
00116     private:
00117         /**
00118          * Function: output
00119          *  Configures sda pin as output
00120          */
00121         void output(void);
00122     
00123         /**
00124          * Function: input
00125          *  Configures sda pin as input
00126          */
00127         void input(void);
00128     
00129         /**
00130          * Function: sda
00131          *  Drive sda pin.
00132          *
00133          * Variables:
00134          *  value - drive pin high or low
00135          */
00136         void sda(bool value);
00137     
00138         /**
00139          * Function: scl
00140          *  Drive scl pin.
00141          *
00142          * Variables:
00143          *  value - drive pin high or low
00144          */
00145         void scl(bool value);
00146     
00147         /**
00148          * Function: shift_out
00149          *  Write single bit out on the SHTx::I2C bus
00150          *
00151          * Variables:
00152          *  bit - value of the bit to be written.
00153          */
00154         void shift_out(bool bit);
00155     
00156         /**
00157          * Function: shift_in
00158          *  Read single bit from the SHTx::I2C bus
00159          *
00160          * Variables:
00161          *  return - value of the bit read.
00162          */
00163         bool shift_in(void);
00164     };
00165 }
00166 
00167 /* !_I2C_HPP_ */
00168 #endif