tool/mbed/mbed-sdk/libraries/tests/peripherals/SRF08/SRF08.cpp

   1
   2 /*
   3 Copyright (c) 2010 Chris Styles ( chris dot styles at mbed dot org )
   4
   5 Permission is hereby granted, free of charge, to any person obtaining a copy
   6 of this software and associated documentation files (the "Software"), to deal
   7 in the Software without restriction, including without limitation the rights
   8 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   9 copies of the Software, and to permit persons to whom the Software is
  10 furnished to do so, subject to the following conditions:
  11
  12 The above copyright notice and this permission notice shall be included in
  13 all copies or substantial portions of the Software.
  14
  15 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  18 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  20 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  21 THE SOFTWARE.
  22 */
  23
  24 #include "SRF08.h"
  25
  26
  27 SRF08::SRF08(PinName sda, PinName scl, int addr) : m_i2c(sda, scl), m_addr(addr) {
  28     char cmd[2];
  29
  30 // Set up SRF08 max range and receiver sensitivity over I2C bus
  31     cmd[0] = 0x02;                          // Range register
  32     cmd[1] = 0x1C;                          // Set max range about 100cm
  33     m_i2c.write(m_addr, cmd, 2);
  34     cmd[0] = 0x01;                          // Receiver gain register
  35     cmd[1] = 0x1B;                          // Set max receiver gain
  36     m_i2c.write(m_addr, cmd, 2);
  37
  38 }
  39
  40 SRF08::~SRF08() {
  41
  42 }
  43
  44 float SRF08::read() {
  45
  46     char cmd[2];
  47     char echo[2];
  48
  49
  50 // Get range data from SRF08
  51 // Send Tx burst command over I2C bus
  52     cmd[0] = 0x00;                      // Command register
  53     cmd[1] = 0x51;                      // Ranging results in cm
  54     m_i2c.write(m_addr, cmd, 2);          // Send ranging burst
  55
  56     wait(0.07);                         // Wait for return echo
  57
  58 // Read back range over I2C bus
  59     cmd[0] = 0x02;                        // Address of first echo
  60     m_i2c.write(m_addr, cmd, 1, 1);         // Send address of first echo
  61     m_i2c.read(m_addr, echo, 2);            // Read two-byte echo result
  62
  63 // Generate PWM mark/space ratio from range data
  64     float range = (echo[0]<<8)+echo[1];
  65
  66     return range;
  67 }