SCA3000 triple axis digital interface accelerometer
SCA3000.cpp@1:f5f2e79304fb, 2011-06-09 (annotated)
- Committer:
- aberk
- Date:
- Thu Jun 09 14:29:16 2011 +0000
- Revision:
- 1:f5f2e79304fb
- Parent:
- 0:fe041345c169
Added functionality for getting the acceleration values in raw counts as opposed to milli-gs.
Who changed what in which revision?
User | Revision | Line number | New contents of line |
---|---|---|---|
aberk | 0:fe041345c169 | 1 | /** |
aberk | 0:fe041345c169 | 2 | * @author Aaron Berk |
aberk | 0:fe041345c169 | 3 | * |
aberk | 0:fe041345c169 | 4 | * @section LICENSE |
aberk | 0:fe041345c169 | 5 | * |
aberk | 0:fe041345c169 | 6 | * Permission is hereby granted, free of charge, to any person obtaining a copy |
aberk | 0:fe041345c169 | 7 | * of this software and associated documentation files (the "Software"), to deal |
aberk | 0:fe041345c169 | 8 | * in the Software without restriction, including without limitation the rights |
aberk | 0:fe041345c169 | 9 | * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
aberk | 0:fe041345c169 | 10 | * copies of the Software, and to permit persons to whom the Software is |
aberk | 0:fe041345c169 | 11 | * furnished to do so, subject to the following conditions: |
aberk | 0:fe041345c169 | 12 | * |
aberk | 0:fe041345c169 | 13 | * The above copyright notice and this permission notice shall be included in |
aberk | 0:fe041345c169 | 14 | * all copies or substantial portions of the Software. |
aberk | 0:fe041345c169 | 15 | * |
aberk | 0:fe041345c169 | 16 | * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
aberk | 0:fe041345c169 | 17 | * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
aberk | 0:fe041345c169 | 18 | * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
aberk | 0:fe041345c169 | 19 | * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
aberk | 0:fe041345c169 | 20 | * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
aberk | 0:fe041345c169 | 21 | * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
aberk | 0:fe041345c169 | 22 | * THE SOFTWARE. |
aberk | 0:fe041345c169 | 23 | * |
aberk | 0:fe041345c169 | 24 | * @section DESCRIPTION |
aberk | 0:fe041345c169 | 25 | * |
aberk | 0:fe041345c169 | 26 | * SCA3000, triple axis, digital interface, accelerometer. |
aberk | 0:fe041345c169 | 27 | * |
aberk | 0:fe041345c169 | 28 | * Datasheet: |
aberk | 0:fe041345c169 | 29 | * |
aberk | 0:fe041345c169 | 30 | * http://www.sparkfun.com/datasheets/Sensors/Accelerometer/SCA3000-D01.pdf |
aberk | 0:fe041345c169 | 31 | */ |
aberk | 0:fe041345c169 | 32 | |
aberk | 0:fe041345c169 | 33 | /** |
aberk | 0:fe041345c169 | 34 | * Includes |
aberk | 0:fe041345c169 | 35 | */ |
aberk | 0:fe041345c169 | 36 | #include "SCA3000.h" |
aberk | 0:fe041345c169 | 37 | |
aberk | 0:fe041345c169 | 38 | SCA3000::SCA3000(PinName mosi, |
aberk | 0:fe041345c169 | 39 | PinName miso, |
aberk | 0:fe041345c169 | 40 | PinName sck, |
aberk | 0:fe041345c169 | 41 | PinName cs, |
aberk | 0:fe041345c169 | 42 | PinName nr) : spi_(mosi, miso, sck), nCS_(cs), nR_(nr) { |
aberk | 0:fe041345c169 | 43 | |
aberk | 0:fe041345c169 | 44 | //1MHz rate. |
aberk | 0:fe041345c169 | 45 | spi_.frequency(1000000); |
aberk | 0:fe041345c169 | 46 | //8-bit frame, POL = 0, PHA = 0. |
aberk | 0:fe041345c169 | 47 | spi_.format(8,0); |
aberk | 0:fe041345c169 | 48 | //Chip select is active low [so set it high initially]. |
aberk | 0:fe041345c169 | 49 | nCS_ = 1; |
aberk | 0:fe041345c169 | 50 | //Pulse reset. |
aberk | 0:fe041345c169 | 51 | nR_ = 0; |
aberk | 0:fe041345c169 | 52 | wait(0.1); |
aberk | 0:fe041345c169 | 53 | nR_ = 1; |
aberk | 0:fe041345c169 | 54 | |
aberk | 0:fe041345c169 | 55 | int status = 0; |
aberk | 0:fe041345c169 | 56 | //Check whether the device successfully reset by reading |
aberk | 0:fe041345c169 | 57 | //the CSME bit of the STATUS register. |
aberk | 0:fe041345c169 | 58 | //0 => no error |
aberk | 0:fe041345c169 | 59 | //1 => error |
aberk | 0:fe041345c169 | 60 | status = oneByteRead(SCA3000_STATUS_REG); |
aberk | 0:fe041345c169 | 61 | //CSME bit = 1... uh oh... |
aberk | 0:fe041345c169 | 62 | if (status & 0x2) { |
aberk | 0:fe041345c169 | 63 | |
aberk | 0:fe041345c169 | 64 | } |
aberk | 0:fe041345c169 | 65 | |
aberk | 0:fe041345c169 | 66 | } |
aberk | 0:fe041345c169 | 67 | |
aberk | 0:fe041345c169 | 68 | int SCA3000::getRevId(void) { |
aberk | 0:fe041345c169 | 69 | |
aberk | 0:fe041345c169 | 70 | return oneByteRead(SCA3000_REVID_REG); |
aberk | 0:fe041345c169 | 71 | |
aberk | 0:fe041345c169 | 72 | } |
aberk | 0:fe041345c169 | 73 | |
aberk | 0:fe041345c169 | 74 | float SCA3000::getAcceleration(int axis) { |
aberk | 0:fe041345c169 | 75 | |
aberk | 1:f5f2e79304fb | 76 | return getCounts(axis) * 0.75; |
aberk | 1:f5f2e79304fb | 77 | |
aberk | 1:f5f2e79304fb | 78 | } |
aberk | 1:f5f2e79304fb | 79 | |
aberk | 1:f5f2e79304fb | 80 | int SCA3000::getCounts(int axis){ |
aberk | 1:f5f2e79304fb | 81 | |
aberk | 0:fe041345c169 | 82 | int acceleration = 0; |
aberk | 0:fe041345c169 | 83 | int axis_lsb = 0; |
aberk | 0:fe041345c169 | 84 | int axis_msb = 0; |
aberk | 0:fe041345c169 | 85 | |
aberk | 0:fe041345c169 | 86 | switch (axis) { |
aberk | 0:fe041345c169 | 87 | |
aberk | 0:fe041345c169 | 88 | case SCA3000_X_AXIS: |
aberk | 0:fe041345c169 | 89 | |
aberk | 0:fe041345c169 | 90 | axis_lsb = oneByteRead(SCA3000_X_LSB); |
aberk | 0:fe041345c169 | 91 | axis_msb = oneByteRead(SCA3000_X_MSB); |
aberk | 0:fe041345c169 | 92 | |
aberk | 0:fe041345c169 | 93 | break; |
aberk | 0:fe041345c169 | 94 | |
aberk | 0:fe041345c169 | 95 | case SCA3000_Y_AXIS: |
aberk | 0:fe041345c169 | 96 | |
aberk | 0:fe041345c169 | 97 | axis_lsb = oneByteRead(SCA3000_Y_LSB); |
aberk | 0:fe041345c169 | 98 | axis_msb = oneByteRead(SCA3000_Y_MSB); |
aberk | 0:fe041345c169 | 99 | |
aberk | 0:fe041345c169 | 100 | break; |
aberk | 0:fe041345c169 | 101 | |
aberk | 0:fe041345c169 | 102 | case SCA3000_Z_AXIS: |
aberk | 0:fe041345c169 | 103 | |
aberk | 0:fe041345c169 | 104 | axis_lsb = oneByteRead(SCA3000_Z_LSB); |
aberk | 0:fe041345c169 | 105 | axis_msb = oneByteRead(SCA3000_Z_MSB); |
aberk | 0:fe041345c169 | 106 | |
aberk | 0:fe041345c169 | 107 | break; |
aberk | 0:fe041345c169 | 108 | |
aberk | 0:fe041345c169 | 109 | //An invalid axis value has been passed. |
aberk | 0:fe041345c169 | 110 | default: |
aberk | 0:fe041345c169 | 111 | |
aberk | 0:fe041345c169 | 112 | break; |
aberk | 0:fe041345c169 | 113 | |
aberk | 0:fe041345c169 | 114 | } |
aberk | 0:fe041345c169 | 115 | |
aberk | 1:f5f2e79304fb | 116 | int counts = ( axis_msb << 8 | axis_lsb ); |
aberk | 1:f5f2e79304fb | 117 | |
aberk | 0:fe041345c169 | 118 | //If this looks like nonsense it's because |
aberk | 0:fe041345c169 | 119 | //the datasheet is completely wrong. |
aberk | 0:fe041345c169 | 120 | if(counts & 0x8000){ |
aberk | 0:fe041345c169 | 121 | counts = (counts >> 3) & 0x1FFF; |
aberk | 1:f5f2e79304fb | 122 | counts = (~counts & 0x1FFF) + 1; |
aberk | 1:f5f2e79304fb | 123 | acceleration = counts * -1; |
aberk | 0:fe041345c169 | 124 | } |
aberk | 0:fe041345c169 | 125 | else{ |
aberk | 0:fe041345c169 | 126 | counts = (counts >> 3) & 0xFFF; |
aberk | 1:f5f2e79304fb | 127 | acceleration = counts; |
aberk | 0:fe041345c169 | 128 | } |
aberk | 0:fe041345c169 | 129 | |
aberk | 0:fe041345c169 | 130 | return acceleration; |
aberk | 1:f5f2e79304fb | 131 | |
aberk | 0:fe041345c169 | 132 | } |
aberk | 0:fe041345c169 | 133 | |
aberk | 0:fe041345c169 | 134 | int SCA3000::oneByteRead(int address) { |
aberk | 0:fe041345c169 | 135 | |
aberk | 0:fe041345c169 | 136 | //Register address sits in the first 6 bits of the transmission. |
aberk | 0:fe041345c169 | 137 | int tx = ((address << 2) | SCA3000_SPI_READ); |
aberk | 0:fe041345c169 | 138 | int rx = 0; |
aberk | 0:fe041345c169 | 139 | |
aberk | 0:fe041345c169 | 140 | nCS_ = 0; |
aberk | 0:fe041345c169 | 141 | //Send address to read from. |
aberk | 0:fe041345c169 | 142 | spi_.write(tx); |
aberk | 0:fe041345c169 | 143 | //Read back contents of address. |
aberk | 0:fe041345c169 | 144 | rx = spi_.write(0x00); |
aberk | 0:fe041345c169 | 145 | nCS_ = 1; |
aberk | 0:fe041345c169 | 146 | |
aberk | 0:fe041345c169 | 147 | return rx; |
aberk | 0:fe041345c169 | 148 | |
aberk | 0:fe041345c169 | 149 | } |
aberk | 0:fe041345c169 | 150 | |
aberk | 0:fe041345c169 | 151 | void SCA3000::oneByteWrite(int address, char data) { |
aberk | 0:fe041345c169 | 152 | |
aberk | 0:fe041345c169 | 153 | //Register address sits in the first 6 bits of the transmission. |
aberk | 0:fe041345c169 | 154 | int tx = ((address << 2) | SCA3000_SPI_WRITE); |
aberk | 0:fe041345c169 | 155 | |
aberk | 0:fe041345c169 | 156 | nCS_ = 0; |
aberk | 0:fe041345c169 | 157 | //Send address to write to. |
aberk | 0:fe041345c169 | 158 | spi_.write(tx); |
aberk | 0:fe041345c169 | 159 | //Send data to be written. |
aberk | 0:fe041345c169 | 160 | spi_.write(data); |
aberk | 0:fe041345c169 | 161 | nCS_ = 1; |
aberk | 0:fe041345c169 | 162 | |
aberk | 0:fe041345c169 | 163 | } |