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HealthThermometerService.h
1 /* mbed Microcontroller Library
2  * Copyright (c) 2006-2020 ARM Limited
3  *
4  * SPDX-License-Identifier: Apache-2.0
5  *
6  * Licensed under the Apache License, Version 2.0 (the "License");
7  * you may not use this file except in compliance with the License.
8  * You may obtain a copy of the License at
9  *
10  * http://www.apache.org/licenses/LICENSE-2.0
11  *
12  * Unless required by applicable law or agreed to in writing, software
13  * distributed under the License is distributed on an "AS IS" BASIS,
14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15  * See the License for the specific language governing permissions and
16  * limitations under the License.
17  */
18 
19 #ifndef __BLE_HEALTH_THERMOMETER_SERVICE_H__
20 #define __BLE_HEALTH_THERMOMETER_SERVICE_H__
21 
22 #include "ble/BLE.h"
23 #include "ble/Gap.h"
24 #include "ble/GattServer.h"
25 
26 #if BLE_FEATURE_GATT_SERVER
27 
28 /**
29 * @class HealthThermometerService
30 * @brief BLE Health Thermometer Service. This service provides the location of the thermometer and the temperature.
31 * Service: https://developer.bluetooth.org/gatt/profiles/Pages/ProfileViewer.aspx?u=org.bluetooth.profile.health_thermometer.xml
32 * Temperature Measurement: https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.temperature_measurement.xml
33 * Temperature Type: https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.temperature_type.xml
34 */
35 class HealthThermometerService {
36 public:
37  /**
38  * @brief Location of sensor on the body.
39  */
40  enum SensorLocation_t {
41  LOCATION_ARMPIT = 1, /*!< Armpit. */
42  LOCATION_BODY, /*!< Body. */
43  LOCATION_EAR, /*!< Ear. */
44  LOCATION_FINGER, /*!< Finger. */
45  LOCATION_GI_TRACT, /*!< GI tract */
46  LOCATION_MOUTH, /*!< Mouth. */
47  LOCATION_RECTUM, /*!< Rectum. */
48  LOCATION_TOE, /*!< Toe. */
49  LOCATION_EAR_DRUM, /*!< Eardrum. */
50  };
51 
52 public:
53  /**
54  * @brief Add the Health Thermometer Service to an existing BLE object, initialize with temperature and location.
55  * @param[in] _ble Reference to the BLE device.
56  * @param[in] initialTemp Initial value in celsius.
57  * @param[in] _location
58  */
59  HealthThermometerService(BLE &_ble, float initialTemp, uint8_t _location) :
60  ble(_ble),
61  valueBytes(initialTemp),
62  tempMeasurement(GattCharacteristic::UUID_TEMPERATURE_MEASUREMENT_CHAR, (TemperatureValueBytes *)valueBytes.getPointer(), GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_INDICATE),
63  tempLocation(GattCharacteristic::UUID_TEMPERATURE_TYPE_CHAR, &_location) {
64 
65  GattCharacteristic *hrmChars[] = {&tempMeasurement, &tempLocation, };
66  GattService hrmService(GattService::UUID_HEALTH_THERMOMETER_SERVICE, hrmChars, sizeof(hrmChars) / sizeof(hrmChars[0]));
67 
68  ble.gattServer().addService(hrmService);
69  }
70 
71  /**
72  * @brief Update the temperature being broadcast.
73  *
74  * @param[in] temperature
75  * Floating point value of the temperature.
76  *
77  */
78  void updateTemperature(float temperature) {
79  valueBytes.updateTemperature(temperature);
80  ble.gattServer().write(tempMeasurement.getValueHandle(), valueBytes.getPointer(), sizeof(TemperatureValueBytes));
81  }
82 
83  /**
84  * @brief Update the location.
85  * @param loc
86  * New location value.
87  */
88  void updateLocation(SensorLocation_t loc) {
89  ble.gattServer().write(tempLocation.getValueHandle(), reinterpret_cast<uint8_t *>(&loc), sizeof(uint8_t));
90  }
91 
92 private:
93  /* Private internal representation for the bytes used to work with the vaulue of the temperature characteristic. */
94  struct TemperatureValueBytes {
95  static const unsigned OFFSET_OF_FLAGS = 0;
96  static const unsigned OFFSET_OF_VALUE = OFFSET_OF_FLAGS + sizeof(uint8_t);
97  static const unsigned SIZEOF_VALUE_BYTES = sizeof(uint8_t) + sizeof(float);
98 
99  static const unsigned TEMPERATURE_UNITS_FLAG_POS = 0;
100  static const unsigned TIMESTAMP_FLAG_POS = 1;
101  static const unsigned TEMPERATURE_TYPE_FLAG_POS = 2;
102 
103  static const uint8_t TEMPERATURE_UNITS_CELSIUS = 0;
104  static const uint8_t TEMPERATURE_UNITS_FAHRENHEIT = 1;
105 
106  TemperatureValueBytes(float initialTemperature) : bytes() {
107  /* Assumption: temperature values are expressed in celsius */
108  bytes[OFFSET_OF_FLAGS] = (TEMPERATURE_UNITS_CELSIUS << TEMPERATURE_UNITS_FLAG_POS) |
109  (false << TIMESTAMP_FLAG_POS) |
110  (false << TEMPERATURE_TYPE_FLAG_POS);
111  updateTemperature(initialTemperature);
112  }
113 
114  void updateTemperature(float temp) {
115  uint32_t temp_ieee11073 = quick_ieee11073_from_float(temp);
116  memcpy(&bytes[OFFSET_OF_VALUE], &temp_ieee11073, sizeof(float));
117  }
118 
119  uint8_t *getPointer() {
120  return bytes;
121  }
122 
123  const uint8_t *getPointer() const {
124  return bytes;
125  }
126 
127 private:
128  /**
129  * @brief A very quick conversion between a float temperature and 11073-20601 FLOAT-Type.
130  * @param temperature The temperature as a float.
131  * @return The temperature in 11073-20601 FLOAT-Type format.
132  */
133  static uint32_t quick_ieee11073_from_float(float temperature) {
134  uint8_t exponent = 0xFE; //Exponent is -2
135  uint32_t mantissa = (uint32_t)(temperature * 100);
136 
137  return (((uint32_t)exponent) << 24) | mantissa;
138  }
139 
140 private:
141  /* First byte: 8-bit flags. Second field is a float holding the temperature value. */
142  /* See https://developer.bluetooth.org/gatt/characteristics/Pages/CharacteristicViewer.aspx?u=org.bluetooth.characteristic.temperature_measurement.xml */
143  uint8_t bytes[SIZEOF_VALUE_BYTES];
144  };
145 
146 protected:
147  BLE &ble;
148  TemperatureValueBytes valueBytes;
149  ReadOnlyGattCharacteristic<TemperatureValueBytes> tempMeasurement;
150  ReadOnlyGattCharacteristic<uint8_t> tempLocation;
151 };
152 
153 #endif // BLE_FEATURE_GATT_SERVER
154 
155 #endif /* #ifndef __BLE_HEALTH_THERMOMETER_SERVICE_H__*/
HealthThermometerService::updateTemperature
void updateTemperature(float temperature)
Update the temperature being broadcast.
Definition: HealthThermometerService.h:78
GattService::UUID_HEALTH_THERMOMETER_SERVICE
UUID of the health thermometer.
Definition: gatt/GattService.h:86
GattCharacteristic::getValueHandle
GattAttribute::Handle_t getValueHandle() const
Get the characteristic&#39;s value attribute handle in the ATT table.
Definition: gatt/GattCharacteristic.h:1730
HealthThermometerService::SensorLocation_t
SensorLocation_t
Location of sensor on the body.
Definition: HealthThermometerService.h:40
HealthThermometerService
BLE Health Thermometer Service.
Definition: HealthThermometerService.h:35
GattCharacteristic
Representation of a GattServer characteristic.
Definition: gatt/GattCharacteristic.h:105
HealthThermometerService::updateLocation
void updateLocation(SensorLocation_t loc)
Update the location.
Definition: HealthThermometerService.h:88
GattService
Representation of a GattServer service.
Definition: gatt/GattService.h:40
ble
Entry namespace for all BLE API definitions.
Definition: CyH4TransportDriver.h:29
ble::BLE
Abstract away BLE-capable radio transceivers or SOCs.
Definition: BLE.h:137
HealthThermometerService::HealthThermometerService
HealthThermometerService(BLE &_ble, float initialTemp, uint8_t _location)
Add the Health Thermometer Service to an existing BLE object, initialize with temperature and locatio...
Definition: HealthThermometerService.h:59
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