linux: hearing aid support (#230)

* linux: add hearing aid

it's just a simple python script, with a toggle in the main app. i dont want to mess with the main app because it uses ATT instead of the AACP protocol which is implemented in the app.

* linux: implement adding hearing aid test results

* docs: add linux screenshot

* docs: add linux hearing aid script

* linux: add reset button for hearing aid adjustments

* linux: remove MAC address logging for security

Author: kavishdevar

linux/Main.qml

@@ -156,6 +156,13 @@ ApplicationWindow {
                     checked: airPodsTrayApp.deviceInfo.conversationalAwareness
                     onCheckedChanged: airPodsTrayApp.setConversationalAwareness(checked)
                 }
+
+                Switch {
+                    visible: airPodsTrayApp.airpodsConnected
+                    text: "Hearing Aid"
+                    checked: airPodsTrayApp.deviceInfo.hearingAidEnabled
+                    onCheckedChanged: airPodsTrayApp.setHearingAidEnabled(checked)
+                }
             }
 
             RoundButton {

linux/README.md

@@ -6,7 +6,10 @@ A native Linux application to control your AirPods, with support for:
 - Conversational Awareness
 - Battery monitoring
 - Auto play/pause on ear detection
-- Seamless handoff between phone and PC
+- Hearing Aid features
+   - Supports adjusting hearing aid- amplification, balance, tone, ambient noise reduction, own voice amplification, and conversation boost
+   - Supports setting the values for left and right hearing aids (this is not a hearing test! you need to have an audiogram to set the values)
+- Seamless handoff between Android and Linux
 
 ## Prerequisites
 
@@ -97,3 +100,35 @@ systemctl --user enable --now mpris-proxy
   - Switch between noise control modes
   - View battery levels
   - Control playback
+
+## Hearing Aid
+
+To use hearing aid features, you need to have an audiogram. To enable/disable hearing aid, you can use the toggle in the main app. But, to adjust the settings and set the audiogram, you need to use a different script which is located in this folder as `hearing_aid.py`. You can run it with:
+
+```bash
+python3 hearing_aid.py
+```
+
+The script will load the current settings from the AirPods and allow you to adjust them. You can set the audiogram by providing the values for 8 frequencies (250Hz, 500Hz, 1kHz, 2kHz, 3kHz, 4kHz, 6kHz, 8kHz) for both left and right ears. There are also options to adjust amplification, balance, tone, ambient noise reduction, own voice amplification, and conversation boost.
+
+AirPods check for the DeviceID characteristic to see if the connected device is an Apple device and only then allow hearing aid features. To set the DeviceID characteristic, you need to add this line to your bluetooth configuration file (usually located at `/etc/bluetooth/main.conf`):
+
+```
+DeviceID = bluetooth:004C:0000:0000
+```
+
+Then, restart the bluetooth service:
+
+```bash
+sudo systemctl restart bluetooth
+```
+
+Here, you might need to re-pair your AirPods because they seem to cache this info.
+
+### Troubleshooting
+
+It is possible that the AirPods disconnect after a short period of time and play the disconnect sound. This is likely due to the AirPods expecting some information from an Apple device. Since I have not implemented everything that an Apple device does, the AirPods may disconnect. You don't need to reconnect them manually; the script will handle reconnection automatically for hearing aid features. So, once you are done setting the hearing aid features, change back the `DeviceID` to whatever it was before.
+
+### Why a separate script?
+
+Because I discovered that QBluetooth doesn't support connecting to a socket with its PSM, only a UUID can be used. I could add a dependency on BlueZ, but then having two bluetooth interfaces seems unnecessary. So, I decided to use a separate script for hearing aid features. In the future, QBluetooth will be replaced with BlueZ native calls, and then everything will be in one application.

linux/airpods_packets.h

@@ -107,6 +107,16 @@ namespace AirPodsPackets
         inline std::optional<bool> parseState(const QByteArray &data) { return Type::parseState(data); }
     }
 
+    // Hearing Aid
+    namespace HearingAid
+    {
+        using Type = BasicControlCommand<0x2C>;
+        static const QByteArray ENABLED = Type::ENABLED;
+        static const QByteArray DISABLED = Type::DISABLED;
+        static const QByteArray HEADER = Type::HEADER;
+        inline std::optional<bool> parseState(const QByteArray &data) { return Type::parseState(data); }
+    }
+
     // Allow Off Option
     namespace AllowOffOption
     {

linux/deviceinfo.hpp

@@ -15,6 +15,7 @@ class DeviceInfo : public QObject
     Q_PROPERTY(QString batteryStatus READ batteryStatus WRITE setBatteryStatus NOTIFY batteryStatusChanged)
     Q_PROPERTY(int noiseControlMode READ noiseControlModeInt WRITE setNoiseControlModeInt NOTIFY noiseControlModeChangedInt)
     Q_PROPERTY(bool conversationalAwareness READ conversationalAwareness WRITE setConversationalAwareness NOTIFY conversationalAwarenessChanged)
+    Q_PROPERTY(bool hearingAidEnabled READ hearingAidEnabled WRITE setHearingAidEnabled NOTIFY hearingAidEnabledChanged)
     Q_PROPERTY(int adaptiveNoiseLevel READ adaptiveNoiseLevel WRITE setAdaptiveNoiseLevel NOTIFY adaptiveNoiseLevelChanged)
     Q_PROPERTY(QString deviceName READ deviceName WRITE setDeviceName NOTIFY deviceNameChanged)
     Q_PROPERTY(Battery *battery READ getBattery CONSTANT)
@@ -67,6 +68,16 @@ class DeviceInfo : public QObject
         }
     }
 
+    bool hearingAidEnabled() const { return m_hearingAidEnabled; }
+    void setHearingAidEnabled(bool enabled)
+    {
+        if (m_hearingAidEnabled != enabled)
+        {
+            m_hearingAidEnabled = enabled;
+            emit hearingAidEnabledChanged(enabled);
+        }
+    }
+
     int adaptiveNoiseLevel() const { return m_adaptiveNoiseLevel; }
     void setAdaptiveNoiseLevel(int level)
     {
@@ -159,6 +170,7 @@ class DeviceInfo : public QObject
         setNoiseControlMode(NoiseControlMode::Off);
         setBluetoothAddress("");
         getEarDetection()->reset();
+        setHearingAidEnabled(false);
     }
 
     void saveToSettings(QSettings &settings)
@@ -168,6 +180,7 @@ class DeviceInfo : public QObject
         settings.setValue("model", static_cast<int>(model()));
         settings.setValue("magicAccIRK", magicAccIRK());
         settings.setValue("magicAccEncKey", magicAccEncKey());
+        settings.setValue("hearingAidEnabled", hearingAidEnabled());
         settings.endGroup();
     }
     void loadFromSettings(const QSettings &settings)
@@ -176,6 +189,7 @@ class DeviceInfo : public QObject
         setModel(static_cast<AirPodsModel>(settings.value("DeviceInfo/model", (int)(AirPodsModel::Unknown)).toInt()));
         setMagicAccIRK(settings.value("DeviceInfo/magicAccIRK", QByteArray()).toByteArray());
         setMagicAccEncKey(settings.value("DeviceInfo/magicAccEncKey", QByteArray()).toByteArray());
+        setHearingAidEnabled(settings.value("DeviceInfo/hearingAidEnabled", false).toBool());
     }
 
     void updateBatteryStatus()
@@ -191,6 +205,7 @@ class DeviceInfo : public QObject
     void noiseControlModeChanged(NoiseControlMode mode);
     void noiseControlModeChangedInt(int mode);
     void conversationalAwarenessChanged(bool enabled);
+    void hearingAidEnabledChanged(bool enabled);
     void adaptiveNoiseLevelChanged(int level);
     void deviceNameChanged(const QString &name);
     void primaryChanged();
@@ -202,6 +217,7 @@ class DeviceInfo : public QObject
     QString m_batteryStatus;
     NoiseControlMode m_noiseControlMode = NoiseControlMode::Transparency;
     bool m_conversationalAwareness = false;
+    bool m_hearingAidEnabled = false;
     int m_adaptiveNoiseLevel = 50;
     QString m_deviceName;
     Battery *m_battery;