locator_receiver/utility/AvrI2c.h

   1 /* Arduino SSD1306Ascii Library
   2  * Copyright (C) 2015 by William Greiman
   3  *
   4  * This file is part of the Arduino SSD1306Ascii Library
   5  *
   6  * This Library is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This Library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with the Arduino SSD1306Ascii Library.  If not, see
  18  * <http://www.gnu.org/licenses/>.
  19  */
  20 /**
  21  * @file AvrI2c.h
  22  * @brief Small fast I2C class for AVR.
  23  */
  24 #ifndef AvrI2c_h
  25 #define AvrI2c_h
  26 #include <Arduino.h>
  27
  28 /** Bit to or with address for read start and read restart */
  29 uint8_t const I2C_READ = 1;
  30
  31 /** Bit to or with address for write start and write restart */
  32 uint8_t const I2C_WRITE = 0;
  33 //------------------------------------------------------------------------------
  34 // Status codes in TWSR - names are from Atmel TWSR.h with TWSR_ added
  35
  36 /** start condition transmitted */
  37 uint8_t const TWSR_START = 0x08;
  38
  39 /** repeated start condition transmitted */
  40 uint8_t const TWSR_REP_START = 0x10;
  41
  42 /** slave address plus write bit transmitted, ACK received */
  43 uint8_t const TWSR_MTX_ADR_ACK = 0x18;
  44
  45 /** data transmitted, ACK received */
  46 uint8_t const TWSR_MTX_DATA_ACK = 0x28;
  47
  48 /** slave address plus read bit transmitted, ACK received */
  49 uint8_t const TWSR_MRX_ADR_ACK = 0x40;
  50 //------------------------------------------------------------------------------
  51 /**
  52  * \class AvrI2c
  53  * \brief Hardware I2C master class for AVR.
  54  *
  55  * Uses ATmega TWI hardware port
  56  */
  57 class AvrI2c {
  58  public:
  59   /**
  60    * @brief Initialize prescalar and SLC clock rate.
  61    * @param[in] fastMode Fast 400 kHz mode if true else standard 100 kHz mode.
  62    */
  63   void begin(bool fastMode = true) {
  64     // Zero prescaler.
  65     TWSR = 0;
  66     // Set bit rate.
  67     setClock(fastMode && F_CPU > 15000000 ? 400000 : 100000);
  68   }
  69   /**
  70    * @brief Read a byte and send Ack if more reads follow else
  71              Nak to terminate read.
  72    *
  73    * @param[in] last Set true to terminate the read else false.
  74    * @return The byte read from the I2C bus.
  75    */
  76   uint8_t read(bool last) {
  77     execCmd((1 << TWINT) | (1 << TWEN) | (last ? 0 : (1 << TWEA)));
  78     return TWDR;
  79   }
  80   /**
  81    * @brief Issue a repeated start condition.
  82    *
  83    * same as start with no stop.  Included to document intention.
  84    *
  85    * @param[in] addressRW I2C address with read/write bit.
  86    * @return The value true, 1, for success or false, 0, for failure.
  87    */
  88   bool repeatedStart(uint8_t addressRW) {
  89     return start(addressRW);
  90   }
  91   /**
  92    * @brief Set the I2C bit rate.
  93    *
  94    * @param[in] frequency Desired frequency in Hz.
  95    *            Valid range for a 16 MHz board is about 40 kHz to 444,000 kHz.
  96    */
  97   void setClock(uint32_t frequency) {
  98     TWBR = ((F_CPU / frequency) - 16) / 2;
  99   }
 100   /**
 101    * @brief Issue a start condition.
 102    *
 103    * @param[in] addressRW I2C address with read/write bit.
 104    *
 105    * @return The value true for success or false for failure.
 106    */
 107   bool start(uint8_t addressRW) {
 108     // send START condition
 109     execCmd((1 << TWINT) | (1 << TWSTA) | (1 << TWEN));
 110     if (status() != TWSR_START && status() != TWSR_REP_START) {
 111       return false;
 112     }
 113     // send device address and direction
 114     TWDR = addressRW;
 115     execCmd((1 << TWINT) | (1 << TWEN));
 116     if (addressRW & I2C_READ) {
 117       return status() == TWSR_MRX_ADR_ACK;
 118     } else {
 119       return status() == TWSR_MTX_ADR_ACK;
 120     }
 121   }
 122   /** @return status from last TWI command - useful for library debug */
 123   uint8_t status(void) {return status_;}
 124   /** Issue a stop condition. */
 125   void stop(void) {
 126     TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
 127
 128     // wait until stop condition is executed and bus released
 129     while (TWCR & (1 << TWSTO)) {}
 130   }
 131   /**
 132    * @brief Write a byte.
 133    *
 134    * @param[in] data The byte to send.
 135    *
 136    * @return The value true, 1, if the slave returned an Ack or false for Nak.
 137    */
 138   bool write(uint8_t data) {
 139     TWDR = data;
 140     execCmd((1 << TWINT) | (1 << TWEN));
 141     return status() == TWSR_MTX_DATA_ACK;
 142   }
 143
 144  private:
 145   uint8_t status_;
 146
 147   void execCmd(uint8_t cmdReg) {
 148     // send command
 149     TWCR = cmdReg;
 150     // wait for command to complete
 151     while (!(TWCR & (1 << TWINT))) {}
 152     // status bits.
 153     status_ = TWSR & 0xF8;
 154   }
 155 };
 156 #endif  // AvrI2c_h