Split init and get_data in separate methods

Documentation/pycardium/bme680.rst

 ``bme680`` - 4-in-1 Sensor
 ==========================
 
-.. py:function:: bme680.get_bme_data()
+.. py:function:: bme680.init()
+
+   Before being able to read data from the sensor, you have to call init().
+
+.. py:function:: bme680.get_data()
 
    Does a single measurement to get environmental data.
 

epicardium/epicardium.h

@@ -106,7 +106,8 @@ typedef _Bool bool;
 #define API_PERSONAL_STATE_GET     0xc1
 #define API_PERSONAL_STATE_IS_PERSISTENT 0xc2
 
-#define API_BME680_GET_DATA					 0xD0
+#define API_BME680_INIT            0xD0
+#define API_BME680_GET_DATA	       0xD1
 
 /* clang-format on */
 
@@ -683,6 +684,20 @@ struct bme680_sensor_data {
 	float gas_resistance;
 };
 
+/**
+ * Initialize the BM680 sensor.
+ *
+ * :param data: Where to store the environmental data.
+ * :return: 0 on success or ``-Exxx`` on error.  The following
+ *     errors might occur:
+ *
+ *     - ``-EFAULT``:  On NULL-pointer.
+ *     - ``-EINVAL``:  Invalid configuration.
+ *     - ``-EIO``:  Communication with the device failed.
+ *     - ``-ENODEV``:  Device was not found.
+ */
+API(API_BME680_INIT, int epic_bme680_init());
+
 /**
  * Get the current BME680 data.
  *

epicardium/modules/bme680.c

@@ -15,6 +15,7 @@
 
 static bool initialized;
 static struct bme680_dev bme;
+uint16_t settings_sel;
 
 static int convert_error(int8_t error)
 {
@@ -32,10 +33,8 @@ static int convert_error(int8_t error)
 	}
 }
 
-int epic_bme680_read_sensors(struct bme680_sensor_data *data)
-{
+int epic_bme680_init() {
   int8_t result = BME680_OK;
-  uint16_t settings_sel;
 
   if (__builtin_expect(!initialized, 0)) {
 
@@ -84,7 +83,17 @@ int epic_bme680_read_sensors(struct bme680_sensor_data *data)
 
 		initialized = true;
 	}
+  return 0;
+}
 
+int epic_bme680_read_sensors(struct bme680_sensor_data *data)
+{
+  if(!initialized) {
+    LOG_ERR("bme680", "bme680 sensor not initialized");
+    return -1;
+  }
+
+  int8_t result = BME680_OK;
   struct bme680_field_data raw_data;
 
 	uint16_t profile_dur = 0;

pycardium/modules/bme680.c

@@ -4,7 +4,7 @@
 
 #include "epicardium.h"
 
-static mp_obj_t mp_get_bme_data()
+static mp_obj_t mp_bme680_get_data()
 {
   struct bme680_sensor_data data;
   int ret = epic_bme680_read_sensors(&data);
@@ -21,19 +21,32 @@ static mp_obj_t mp_get_bme_data()
 	};
 	return mp_obj_new_tuple(4, values_list);
 }
-static MP_DEFINE_CONST_FUN_OBJ_0(bme_get_bme_data_obj, mp_get_bme_data);
+static MP_DEFINE_CONST_FUN_OBJ_0(bme680_get_data_obj, mp_bme680_get_data);
 
-static const mp_rom_map_elem_t bme_module_globals_table[] = {
+static mp_obj_t mp_bme680_init()
+{
+  int ret = epic_bme680_init();
+
+	if (ret < 0) {
+		mp_raise_OSError(-ret);
+	}
+
+	return 0;
+}
+static MP_DEFINE_CONST_FUN_OBJ_0(bme680_init_obj, mp_bme680_init);
+
+static const mp_rom_map_elem_t bme680_module_globals_table[] = {
 	{ MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_bme680) },
-	{ MP_ROM_QSTR(MP_QSTR_get_bme_data), MP_ROM_PTR(&bme_get_bme_data_obj) },
+	{ MP_ROM_QSTR(MP_QSTR_init), MP_ROM_PTR(&bme680_init_obj) },
+	{ MP_ROM_QSTR(MP_QSTR_get_data), MP_ROM_PTR(&bme680_get_data_obj) },
 };
-static MP_DEFINE_CONST_DICT(bme_module_globals, bme_module_globals_table);
+static MP_DEFINE_CONST_DICT(bme680_module_globals, bme680_module_globals_table);
 
-const mp_obj_module_t bme_module = {
+const mp_obj_module_t bme680_module = {
 	.base    = { &mp_type_module },
-	.globals = (mp_obj_dict_t *)&bme_module_globals,
+	.globals = (mp_obj_dict_t *)&bme680_module_globals,
 };
 
 
 /* Register the module to make it available in Python */
-MP_REGISTER_MODULE(MP_QSTR_bme680, bme_module, MODULE_BME680_ENABLED);
+MP_REGISTER_MODULE(MP_QSTR_bme680, bme680_module, MODULE_BME680_ENABLED);

pycardium/modules/qstrdefs.h

@@ -76,7 +76,8 @@ Q(stop)
 
 /* bme680 */
 Q(bme680)
-Q(get_bme_data)
+Q(init)
+Q(get_data)
 
 /* file */
 Q(__del__)