68 lines
2.3 KiB
C++
68 lines
2.3 KiB
C++
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/*
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Copyright (c) 2010 Chris Styles ( chris dot styles at mbed dot org )
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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*/
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#include "SRF08.h"
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SRF08::SRF08(PinName sda, PinName scl, int addr) : m_i2c(sda, scl), m_addr(addr) {
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char cmd[2];
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// Set up SRF08 max range and receiver sensitivity over I2C bus
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cmd[0] = 0x02; // Range register
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cmd[1] = 0x1C; // Set max range about 100cm
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m_i2c.write(m_addr, cmd, 2);
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cmd[0] = 0x01; // Receiver gain register
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cmd[1] = 0x1B; // Set max receiver gain
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m_i2c.write(m_addr, cmd, 2);
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}
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SRF08::~SRF08() {
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}
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float SRF08::read() {
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char cmd[2];
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char echo[2];
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// Get range data from SRF08
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// Send Tx burst command over I2C bus
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cmd[0] = 0x00; // Command register
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cmd[1] = 0x51; // Ranging results in cm
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m_i2c.write(m_addr, cmd, 2); // Send ranging burst
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wait(0.07); // Wait for return echo
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// Read back range over I2C bus
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cmd[0] = 0x02; // Address of first echo
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m_i2c.write(m_addr, cmd, 1, 1); // Send address of first echo
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m_i2c.read(m_addr, echo, 2); // Read two-byte echo result
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// Generate PWM mark/space ratio from range data
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float range = (echo[0]<<8)+echo[1];
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return range;
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}
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