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https://github.com/eclipse/upm.git
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max31855: add sensor and documentation on creation of a UPM sensor
Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>
This commit is contained in:
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@ -865,7 +865,8 @@ EXCLUDE_SYMBOLS =
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# command).
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EXAMPLE_PATH = @CMAKE_CURRENT_SOURCE_DIR@/examples/ \
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@CMAKE_CURRENT_SOURCE_DIR@/docs/
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@CMAKE_CURRENT_SOURCE_DIR@/docs/ \
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@CMAKE_CURRENT_SOURCE_DIR@/src/max31855/
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# If the value of the EXAMPLE_PATH tag contains directories, you can use the
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# EXAMPLE_PATTERNS tag to specify one or more wildcard pattern (like *.cpp and
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96
docs/max31855.md
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96
docs/max31855.md
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@ -0,0 +1,96 @@
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Making a UPM module for MAX31855 {#max31855}
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================================
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The Maxim Integrated MAX31855 is a thermocouple amplifier allowing you to read
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from a K type themocouple. My board comes from the Pmod kit form Maxim
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(MAX31855PMB1) but you can get this from many different sources. The adafruit
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people made arduino code already so we'll use that as a
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[reference](https://github.com/adafruit/Adafruit-MAX31855-library/blob/master/Adafruit_MAX31855.cpp).
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### Basics
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This is a spi module so we will use the maa spi functions to build our module.
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First thing to do is to create a tree structure like this in upm/src/max31855:
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* max31855.cxx
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* max31855.h
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* jsupm_max31855.i
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* pyupm_max31855.i
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* CMakeLists.txt
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And then an example file to use & test our lib with in upm/examples/max31855.cxx.
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### Swig
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The .i files are used by swig, there is one for each python & javascript. They
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contain essentially the same thing and are very simple. The only thing to
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change between the javascript & node.js one is the argument to %module.
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@snippet jsupm_max31855.i Interesting
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The %include parameter defines which functions will be available to the
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node/python module created, Whilst the headers inside %{} will be explicitly
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required during compilation. Typically only the top level header is required in
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either of those args.
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### API
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Then we create the header (max31855.h) , a very simple header in our case we
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will have only a very basic api. We provide a getTemp() function which will
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return the same type as in the arduino library, a double.
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@snippet max31855.h Interesting
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Note that the header contains both the io that we will use, the gpio is in this
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case used as the chip select pin.
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### Implementing our API
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In the adafruit library the read function (our chip is a 3pin SPI so only read
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is possible), the spiread32() does all the work. It starts by setting up the io
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so we will do the same in our constructor.
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Note unlike on Arduino, we'll just set a 2Mhz clock and let the chip do the
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work.
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@snippet src/max31855/max31855.cxx Constructor
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Then we also need to implement a nice cleanup in our destructor.
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@snippet src/max31855/max31855.cxx Destructor
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Then to read data, we will use spi_write_buf which will allow us to write a
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whole uint32_t in order to get one back, which is what the arduino code does in
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spiread32. Obviously we set our chip select to low first. Here is the start of
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the implementation of MAX31855::getTemp()
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@snippet src/max31855/max31855.cxx spi
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Then using the arduino code as reference we simply reconstruct form the 4
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uint8_t values a 32bit int value and select only the valuable parts of
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information from that. The MAX31855 datahseet explains exactly which bits are
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useful, we will just do the same as the adafruit code, first checking the error
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bit and then scrapping everything but the 14bit of thermocouple data that are
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useful to us and converting it to a double.
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@snippet src/max31855/max31855.cxx conversion
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### Finalizing
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Our final example, very easy to use api!
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@snippet examples/max31855.cxx Interesting
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### Building
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The we need to add it to the examples/CMakeLists.txt. Only three lines are required
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~~~~~~~~~~~
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add_executable (max31855-example max31855.cxx)
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include_directories (${PROJECT_SOURCE_DIR}/src/max31855)
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target_link_libraries (max31855-example max31855 ${CMAKE_THREAD_LIBS_INIT})
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~~~~~~~~~~~
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Note you dont have to rebuild everything, cmake keeps target lists so if you
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named your example target <modulename>-example you can simply do make
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max31855-example and both the library & example will build.
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@ -3,7 +3,8 @@ Porting a module from Arduino {#porting}
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Porting arduino libraries to libmaa as UPM libraries is usually fairly easy.
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The issues typically come from misunderstanding of how a non real time OS deals
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with interupts and timers. It also highly depends on the sensor.
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with interupts and timers. It also highly depends on the sensor. A concrete
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example is explained in detail on @ref max31855
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### Adding a new module to UPM
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@ -15,6 +15,7 @@ add_executable (oled-1327 oled-1327.cxx)
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add_executable (proximity max44000.cxx)
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add_executable (accelerometer mma7455.cxx)
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add_executable (lcd st7735.cxx)
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add_executable (max31855-example max31855.cxx)
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include_directories (${PROJECT_SOURCE_DIR}/src/hmc5883l)
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include_directories (${PROJECT_SOURCE_DIR}/src/grove)
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@ -28,6 +29,7 @@ include_directories (${PROJECT_SOURCE_DIR}/src/hcsr04)
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include_directories (${PROJECT_SOURCE_DIR}/src/max44000)
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include_directories (${PROJECT_SOURCE_DIR}/src/mma7455)
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include_directories (${PROJECT_SOURCE_DIR}/src/st7735)
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include_directories (${PROJECT_SOURCE_DIR}/src/max31855)
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target_link_libraries (compass hmc5883l ${CMAKE_THREAD_LIBS_INIT})
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target_link_libraries (groveled grove ${CMAKE_THREAD_LIBS_INIT})
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@ -46,3 +48,4 @@ target_link_libraries (oled-1327 i2clcd ${CMAKE_THREAD_LIBS_INIT})
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target_link_libraries (proximity max44000 ${CMAKE_THREAD_LIBS_INIT})
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target_link_libraries (accelerometer mma7455 ${CMAKE_THREAD_LIBS_INIT})
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target_link_libraries (lcd st7735 ${CMAKE_THREAD_LIBS_INIT})
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target_link_libraries (max31855-example max31855 ${CMAKE_THREAD_LIBS_INIT})
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41
examples/max31855.cxx
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41
examples/max31855.cxx
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/*
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* Author: Brendan Le Foll <brendan.le.foll@intel.com>
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* Copyright (c) 2014 Intel Corporation.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <unistd.h>
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#include <iostream>
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#include <signal.h>
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//! [Interesting]
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#include "max31855.h"
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int
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main(int argc, char **argv)
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{
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upm::MAX31855 *temp = new upm::MAX31855(0, 8);
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std::cout << temp->getTemp() << std::endl;
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return 0;
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}
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//! [Interesting]
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5
src/max31855/CMakeLists.txt
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5
src/max31855/CMakeLists.txt
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set (libname "max31855")
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set (libdescription "K type thermistor amplifier")
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set (module_src ${libname}.cxx)
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set (module_h ${libname}.h)
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upm_module_init()
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src/max31855/jsupm_max31855.i
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9
src/max31855/jsupm_max31855.i
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//! [Interesting]
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%module jsupm_max31855
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%{
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#include "max31855.h"
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%}
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%include "max31855.h"
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//! [Interesting]
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src/max31855/max31855.cxx
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103
src/max31855/max31855.cxx
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/*
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* Author: Brendan Le Foll <brendan.le.foll@intel.com>
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* Copyright (c) 2014 Intel Corporation.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#include <iostream>
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#include <unistd.h>
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#include <stdlib.h>
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#include <functional>
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#include <string.h>
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#include "max31855.h"
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using namespace upm;
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//! [Constructor]
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MAX31855::MAX31855(int bus, int cs)
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{
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// initialise chip select as a normal gpio
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m_gpio = maa_gpio_init(cs);
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maa_gpio_dir(m_gpio, MAA_GPIO_OUT);
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// initialise the spi bus with a 2Mhz clock
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m_sensor = maa_spi_init(bus);
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maa_spi_frequency(m_sensor, 2000000);
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}
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//! [Constructor]
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//! [Destructor]
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MAX31855::~MAX31855()
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{
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// close both m_sensor & m_gpio cleanly
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maa_result_t error;
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error = maa_spi_stop(m_sensor);
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if (error != MAA_SUCCESS) {
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maa_result_print(error);
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}
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error = maa_gpio_close(m_gpio);
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if (error != MAA_SUCCESS) {
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maa_result_print(error);
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}
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}
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//! [Destructor]
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double
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MAX31855::getTemp()
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{
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//! [spi]
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// set chip select low
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maa_gpio_write(m_gpio, 0);
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uint8_t buf[4];
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// set our input buffer to 0, this is clean but not required
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memset(buf, 0, sizeof(uint8_t)*4);
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// Write buffer to the spi slave
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uint8_t* x = maa_spi_write_buf(m_sensor, buf, 4);
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//! [spi]
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//! [conversion]
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// Endian correct way of making our char array into an 32bit int
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int32_t temp = (x[0] << 24) | (x[1] << 16) | (x[2] << 8) | x[3];;
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// maa_spi_write_buf does not free the return buffer
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free(x);
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if (temp & 0x7) {
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std::cerr << "Something went very wrong!" << std::endl;
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}
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// scrap all the data we dont care about
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temp >>= 18;
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// LSB = 0.25 degrees C
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double c = (double) temp;
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c *= 0.25;
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//! [conversion]
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// set chip select high
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maa_gpio_write(m_gpio, 1);
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return c;
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}
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69
src/max31855/max31855.h
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69
src/max31855/max31855.h
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/*
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* Author: Brendan Le Foll <brendan.le.foll@intel.com>
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* Copyright (c) 2014 Intel Corporation.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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* NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
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* LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
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* OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
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* WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#pragma once
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#include <string>
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#include <maa/spi.h>
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#include <maa/gpio.h>
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namespace upm {
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/**
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* @brief C++ API for MAX31855
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*
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* This file defines the max31855 SPI sensor
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*
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* @snippet examples/max31855.cxx Interesting
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*
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*/
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//! [Interesting]
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class MAX31855 {
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public:
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/**
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* Instanciates a MAX31855 object
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*
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* @param bus The spi bus to use
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* @param cs The chip select pin
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*/
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MAX31855(int bus, int cs);
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/**
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* MAX31855 object destructor
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*/
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~MAX31855();
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/**
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* Get the distance from the sensor
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*
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* @return value in degrees celcius
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*/
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double getTemp();
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private:
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maa_spi_context m_sensor;
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maa_gpio_context m_gpio;
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};
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//! [Interesting]
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}
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10
src/max31855/pyupm_max31855.i
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10
src/max31855/pyupm_max31855.i
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%module pyupm_max31855
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%include "stdint.i"
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%feature("autodoc", "3");
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%include "max31855.h"
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%{
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#include "max31855.h"
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%}
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