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>

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);
+}
+