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fe318a78d2
Implement a single source file for the following:
* mq2: H2/LPG/CH4/CO/alcohol/smoke/propane/etc
* mq3: Alcohol/benzine/CH4/hexane/LPG/CO
* mq4: CNG (mostly methane)
* mq5: H2/LPG/CH4/CO/alcohol
* mq6: LPG (mostly propane/butane)
* mq7: CO
* mq8: H
* mq9: CO/CH4/LPG
The documentation for these sensors notes that they do not read an exact
gas concentration. Some of the sensors have examples for how to
calibrate with a 'clean air environment' for outputing ppm, but this is
not the case for all mqx sensors. Because of this, the output can be
read as a normalized output (0.0->1.0), raw volts (normalized * aRef),
or a scaled/offset voltage.
Signed-off-by: Noel Eck <noel.eck@intel.com>
128 lines
3.0 KiB
C
128 lines
3.0 KiB
C
/*
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* Author:
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* Copyright (c) 2015 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 <string.h>
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#include <stdlib.h>
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#include "mqx.h"
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mqx_context mqx_init(int16_t pin)
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{
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mqx_context dev = (mqx_context) malloc(sizeof(struct _mqx_context));
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if (dev == NULL)
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return NULL;
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/* Init aio pin */
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dev->aio = mraa_aio_init(pin);
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if (dev->aio == NULL) {
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free(dev);
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return NULL;
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}
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/* Set the ADC ref, scale, and offset defaults */
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dev->m_aRef = 5.0;
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dev->m_scale = 1.0;
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dev->m_offset = 0.0;
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return dev;
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}
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void mqx_close(mqx_context dev)
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{
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mraa_aio_close(dev->aio);
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free(dev);
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}
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upm_result_t mqx_set_aref(const mqx_context dev, float aref)
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{
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dev->m_aRef = aref;
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return UPM_SUCCESS;
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}
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upm_result_t mqx_set_scale(const mqx_context dev, float scale)
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{
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dev->m_scale = scale;
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return UPM_SUCCESS;
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}
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upm_result_t mqx_set_offset(const mqx_context dev, float offset)
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{
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dev->m_offset = offset;
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return UPM_SUCCESS;
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}
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float mqx_get_aref(const mqx_context dev)
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{
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return dev->m_aRef;
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}
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float mqx_get_scale(const mqx_context dev)
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{
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return dev->m_scale;
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}
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float mqx_get_offset(const mqx_context dev)
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{
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return dev->m_offset;
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}
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upm_result_t mqx_get_normalized(const mqx_context dev, float *value)
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{
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*value = mraa_aio_read_float(dev->aio);
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if (*value < 0)
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return UPM_ERROR_OPERATION_FAILED;
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}
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upm_result_t mqx_get_raw_volts(const mqx_context dev, float *value)
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{
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*value = mraa_aio_read_float(dev->aio);
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if (*value < 0)
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return UPM_ERROR_OPERATION_FAILED;
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/* Scale by the ADC reference voltage */
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*value *= dev->m_aRef;
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return UPM_SUCCESS;
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}
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upm_result_t mqx_get_volts(const mqx_context dev, float *value)
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{
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*value = mraa_aio_read_float(dev->aio);
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if (*value < 0)
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return UPM_ERROR_OPERATION_FAILED;
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/* Apply raw scale */
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*value *= dev->m_scale;
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/* Scale to aRef */
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*value *= dev->m_aRef;
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/* Apply the offset in volts */
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*value += dev->m_offset;
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return UPM_SUCCESS;
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}
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