mqx: C gas sensors mq2-mq9

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>

examples/c/CMakeLists.txt

@@ -95,6 +95,7 @@ add_example (urm37-uart)
 add_example (hka5)
 add_example (dfrorp)
 add_example (vdiv)
+add_example (mqx)
 
 # Custom examples
 add_custom_example (nmea_gps_i2c-example-c nmea_gps_i2c.c nmea_gps)

examples/c/mqx.c

@@ -0,0 +1,86 @@
+/*
+ * Author: Jon Trulson <jtrulson@ics.com>
+ * Copyright (c) 2016 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <unistd.h>
+#include <signal.h>
+
+#include "mqx.h"
+
+bool shouldRun = true;
+
+void sig_handler(int signo)
+{
+    if (signo == SIGINT)
+        shouldRun = false;
+}
+
+int main()
+{
+    signal(SIGINT, sig_handler);
+
+    //! [Interesting]
+
+    // Instantiate a mqx sensor on analog pin A0
+    mqx_context sensor = mqx_init(0);
+
+    if (!sensor)
+    {
+        printf("mqx_init() failed.\n");
+        return -1;
+    }
+
+    // Set the aref, scale, and offset
+    mqx_set_aref(sensor, 5.0);
+    mqx_set_scale(sensor, 1.0);
+    mqx_set_offset(sensor, -.1);
+    printf("aRef: %0.03f scale: %0.03f offset: %0.03f\n\n",
+            mqx_get_aref(sensor),
+            mqx_get_scale(sensor),
+            mqx_get_offset(sensor));
+
+    // Every half a second, sample the sensor output
+    while (shouldRun)
+    {
+        float normalized = 0.0;
+        float raw_volts = 0.0;
+        float volts = 0.0;
+
+        mqx_get_normalized(sensor, &normalized);
+        mqx_get_raw_volts(sensor, &raw_volts);
+        mqx_get_volts(sensor, &volts);
+
+        printf("Normalized output: %0.03f, raw mqx sensor output: %0.03f v "
+                "adjusted output: %0.03f v\n", normalized, raw_volts, volts);
+
+        usleep(500000);
+    }
+
+    //! [Interesting]
+
+    printf("Exiting\n");
+
+    mqx_close(sensor);
+
+    return 0;
+}

src/gas/CMakeLists.txt

@@ -1,5 +1,8 @@
-set (libname "gas")
-set (libdescription "Gas sensors")
-set (module_src ${libname}.cxx mq2.cxx mq3.cxx mq4.cxx mq5.cxx mq6.cxx mq7.cxx mq8.cxx mq9.cxx tp401.cxx)
-set (module_hpp ${libname}.hpp mq2.hpp mq3.hpp mq4.hpp mq5.hpp mq6.hpp mq7.hpp mq8.hpp mq9.hpp tp401.hpp)
-upm_module_init()
+upm_mixed_module_init (NAME gas
+    DESCRIPTION "Gas sensors"
+    C_HDR mqx.h
+    C_SRC mqx.c
+    CPP_HDR gas.hpp mq2.hpp mq3.hpp mq4.hpp mq5.hpp mq6.hpp mq7.hpp mq8.hpp mq9.hpp tp401.hpp
+    CPP_SRC gas.cxx mq2.cxx mq3.cxx mq4.cxx mq5.cxx mq6.cxx mq7.cxx mq8.cxx mq9.cxx tp401.cxx
+    FTI_SRC mqx_fti.c
+    REQUIRES mraa)

src/gas/gas.cxx

@@ -65,7 +65,7 @@ int
 Gas::findThreshold (thresholdContext* ctx, unsigned int threshold,
                                 uint16_t * buffer, int len) {
     long sum = 0;
-    for (unsigned int i = 0; i < len; i++) {
+    for (int i = 0; i < len; i++) {
         sum += buffer[i];
     }
 

src/gas/mqx.c

@@ -0,0 +1,127 @@
+/*
+ * Author:
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "mqx.h"
+
+mqx_context mqx_init(int16_t pin)
+{
+    mqx_context dev = (mqx_context) malloc(sizeof(struct _mqx_context));
+
+    if (dev == NULL)
+      return NULL;
+
+    /* Init aio pin */
+    dev->aio = mraa_aio_init(pin);
+
+    if (dev->aio == NULL) {
+        free(dev);
+        return NULL;
+    }
+
+    /* Set the ADC ref, scale, and offset defaults */
+    dev->m_aRef = 5.0;
+    dev->m_scale = 1.0;
+    dev->m_offset = 0.0;
+
+    return dev;
+}
+
+void mqx_close(mqx_context dev)
+{
+    mraa_aio_close(dev->aio);
+    free(dev);
+}
+
+upm_result_t mqx_set_aref(const mqx_context dev, float aref)
+{
+    dev->m_aRef = aref;
+    return UPM_SUCCESS;
+}
+
+upm_result_t mqx_set_scale(const mqx_context dev, float scale)
+{
+    dev->m_scale = scale;
+    return UPM_SUCCESS;
+}
+
+upm_result_t mqx_set_offset(const mqx_context dev, float offset)
+{
+    dev->m_offset = offset;
+    return UPM_SUCCESS;
+}
+
+float mqx_get_aref(const mqx_context dev)
+{
+    return dev->m_aRef;
+}
+
+float mqx_get_scale(const mqx_context dev)
+{
+    return dev->m_scale;
+}
+
+float mqx_get_offset(const mqx_context dev)
+{
+    return dev->m_offset;
+}
+
+upm_result_t mqx_get_normalized(const mqx_context dev, float *value)
+{
+    *value = mraa_aio_read_float(dev->aio);
+    if (*value < 0)
+        return UPM_ERROR_OPERATION_FAILED;
+}
+
+upm_result_t mqx_get_raw_volts(const mqx_context dev, float *value)
+{
+    *value = mraa_aio_read_float(dev->aio);
+    if (*value < 0)
+        return UPM_ERROR_OPERATION_FAILED;
+
+    /* Scale by the ADC reference voltage */
+    *value *= dev->m_aRef;
+
+    return UPM_SUCCESS;
+}
+
+upm_result_t mqx_get_volts(const mqx_context dev, float *value)
+{
+    *value = mraa_aio_read_float(dev->aio);
+    if (*value < 0)
+        return UPM_ERROR_OPERATION_FAILED;
+
+     /* Apply raw scale */
+    *value *= dev->m_scale;
+
+     /* Scale to aRef */
+    *value *= dev->m_aRef;
+
+    /* Apply the offset in volts */
+    *value += dev->m_offset;
+
+    return UPM_SUCCESS;
+}

src/gas/mqx.h

@@ -0,0 +1,153 @@
+/*
+ * Author:
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "upm.h"
+#include "mraa/aio.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * The mqx gas sensor driver can be used to read a wide range of sensors.  The
+ * list below shows the currently supported sensors:
+ *
+ *      mq2: H2/LPG/CH4/CO/alcohol/smoke/propane/etc
+ *          LPG/propane 200-5000 ppm
+ *          butane 300-5000 ppm
+ *          CH4 5000-2000 ppm
+ *          H2 300-5000 ppm
+ *          alcohol 100-2000 ppm
+ *      mq3: Alcohol/benzine/CH4/hexane/LPG/CO .05-10 mg/L
+ *      mq4: CNG (mostly methane) 200-10000 ppm
+ *      mq5: H2/LPG/CH4/CO/alcohol 200-10000 ppm
+ *      mq6: LPG (mostly propane/butane) 200-10000 ppm
+ *      mq7: CO 20-2000 ppm
+ *      mq8: H 100-10000 ppm
+ *      mq9: CO/CH4/LPG 200-1000/10000/10000 ppm
+ *
+ */
+
+/**
+ * driver context
+ */
+typedef struct _mqx_context {
+    /* mraa aio pin context */
+    mraa_aio_context aio;
+    /* Analog voltage reference */
+    float m_aRef;
+    /* Scale */
+    float m_scale;
+    /* Offset in sensor units */
+    float m_offset;
+} *mqx_context;
+
+/**
+ * Initialize analog sensor
+ * @param pin Analog pin
+ * @return sensor context
+ */
+mqx_context mqx_init(int16_t pin);
+
+/**
+ * Analog sensor destructor
+ * @param sensor context pointer
+ */
+void mqx_close(mqx_context dev);
+
+/**
+ * Set ADC reference voltage
+ * @param dev sensor context pointer
+ * @param aref ADC reference voltage
+ * @return Function result code
+ */
+upm_result_t mqx_set_aref(const mqx_context dev, float aref);
+
+/**
+ * Set sensor scale.  This scale is applied to the return value:
+ *     counts = counts * scale
+ * @param dev sensor context pointer
+ * @param scale count scale value used
+ * @return Function result code
+ */
+upm_result_t mqx_set_scale(const mqx_context dev, float scale);
+
+/**
+ * Set sensor offset.  This offset is applied to the return value:
+ *     counts = counts + offset
+ * @param dev sensor context pointer
+ * @param offset count offset value used
+ * @return Function result code
+ */
+upm_result_t mqx_set_offset(const mqx_context dev, float offset);
+
+/**
+ * Get sensor aref
+ * @param dev sensor context pointer
+ * @return Sensor ADC reference voltage
+ */
+float mqx_get_aref(const mqx_context dev);
+
+/**
+ * Get sensor scale
+ * @param dev sensor context pointer
+ * @return Sensor scale
+ */
+float mqx_get_scale(const mqx_context dev);
+
+/**
+ * Get sensor offset
+ * @param dev sensor context pointer
+ * @return Sensor offset
+ */
+float mqx_get_offset(const mqx_context dev);
+
+/**
+ * Read normalized value for sensor
+ * @param dev sensor context pointer
+ * @param *value Normalized value (0.0 -> 1.0)
+ * @return Function result code
+ */
+upm_result_t mqx_get_normalized(const mqx_context dev, float *value);
+
+/**
+ * Read raw voltage from the sensor
+ * @param dev sensor context pointer
+ * @param *value Raw sensor voltage
+ * @return Function result code
+ */
+upm_result_t mqx_get_raw_volts(const mqx_context dev, float *value);
+
+/**
+ * Read scaled/offset voltage from the sensor
+ * @param dev sensor context pointer
+ * @param *value Adjusted sensor voltage
+ * @return Function result code
+ */
+upm_result_t mqx_get_volts(const mqx_context dev, float *value);
+#ifdef __cplusplus
+}
+#endif

src/gas/mqx_fti.c

@@ -0,0 +1,122 @@
+/*
+ * Author:
+ * Copyright (c) 2015 Intel Corporation.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#include <string.h>
+#include <stdlib.h>
+
+#include "mqx.h"
+
+#include "upm_fti.h"
+#include "fti/upm_sensor.h"
+#include "fti/upm_raw.h"
+
+/**
+ * This file implements the Function Table Interface (FTI) for this sensor
+ */
+
+const char upm_mqx_name[] = "MQX";
+const char upm_mqx_description[] = "Analog gas sensor (mqx)";
+const upm_protocol_t upm_mqx_protocol[] = {UPM_ANALOG};
+const upm_sensor_t upm_mqx_category[] = {UPM_RAW};
+
+// forward declarations
+void* upm_mqx_init_str(const char* protocol, const char* params);
+void upm_mqx_close(void* dev);
+const upm_sensor_descriptor_t upm_mqx_get_descriptor();
+upm_result_t upm_mqx_set_offset(const void* dev, float offset);
+upm_result_t upm_mqx_set_scale(const void* dev, float scale);
+upm_result_t upm_mqx_get_value(const void* dev, float *value);
+
+
+/* This sensor implementes 2 function tables */
+/* 1. Generic base function table */
+static const upm_sensor_ft ft_gen =
+{
+    .upm_sensor_init_name = &upm_mqx_init_str,
+    .upm_sensor_close = &upm_mqx_close,
+    .upm_sensor_get_descriptor = &upm_mqx_get_descriptor
+};
+
+/* 2. RAW function table */
+static const upm_raw_ft ft_raw =
+{
+    .upm_raw_set_offset = &upm_mqx_set_offset,
+    .upm_raw_set_scale = &upm_mqx_set_scale,
+    .upm_raw_get_value = &upm_mqx_get_value
+};
+
+const void* upm_mqx_get_ft(upm_sensor_t sensor_type)
+{
+    switch(sensor_type)
+    {
+        case UPM_SENSOR:
+            return &ft_gen;
+        case UPM_RAW:
+            return &ft_raw;
+        default:
+            return NULL;
+    }
+}
+
+const upm_sensor_descriptor_t upm_mqx_get_descriptor()
+{
+    /* Fill in the descriptor */
+    upm_sensor_descriptor_t usd;
+    usd.name = upm_mqx_name;
+    usd.description = upm_mqx_description;
+    usd.protocol_size = 1;
+    usd.protocol = upm_mqx_protocol;
+    usd.category_size = 1;
+    usd.category = upm_mqx_category;
+
+    return usd;
+}
+
+void* upm_mqx_init_str(const char* protocol, const char* params)
+{
+    fprintf(stderr, "String initialization - not implemented, using ain0: %s\n", __FILENAME__);
+
+    return mqx_init(0);
+}
+
+void upm_mqx_close(void* dev)
+{
+    mqx_close((mqx_context)dev);
+}
+
+upm_result_t upm_mqx_get_value(const void* dev, float *value)
+{
+    return mqx_get_volts((mqx_context)dev, value);
+}
+
+upm_result_t upm_mqx_set_offset(const void* dev, float offset)
+{
+    return mqx_set_offset((mqx_context)dev, offset);
+}
+
+upm_result_t upm_mqx_set_scale(const void* dev, float scale)
+{
+    return mqx_set_scale((mqx_context)dev, scale);
+}
+