# Audio Configuration This chapter introduces how to configure and use the multi-channel audio paths on the M1 development board under the GNOME desktop, including: onboard MIC (built-in recording), headset playback/recording, SPK (loudspeaker), EAR (earpiece output), as well as Bluetooth audio and cellular voice call functions. # Hardware Audio Channel Overview The M1/L1 development board's audio hardware includes 2 input channels and 2 output channels, implemented via the onboard SH1.0-4P connector, onboard MEMS devices, and reserved test points on the board. Please ensure the hardware connections are correct before operation. | **Channel Type** | **Channel Name** | **Hardware Location** | **Description** | | --- | --- | --- | --- | | Input | Onboard MIC | MEMS microphone on the mainboard | Built‑in silicon microphone; default recording input source; no external connection required. | | Input & Output | Headset | SH1.0‑4P connector | External headset with microphone. | | Output | SPK (Speaker) | Reserved test points | Drives high‑power external speaker (requires an external amplifier; direct connection to speaker results in low volume). | | Output | EAR (Earpiece) | Reserved test points | Drives low‑power earpiece / headphone. | ```{image} images/image_Vo25bQYqvoSpo5xEzGacswt7nEh.webp :width: 2193px :height: 1546px :align: center ``` ```{image} images/image_YWjdb1coKoroQtxiohwc4PFWnxc.webp :width: 1280px :height: 1000px :align: center ``` --- # Basic System Audio Settings Management of all audio channels is centralized in the GNOME "Sound" settings panel. 1. Click the top-left corner icon to enter the menu interface, and open "Settings". ```{image} images/image_WpYcbY4LforarIxHnSvcSffSnYc.webp :width: 1034px :height: 650px :align: center ``` 2. In the left menu, click the Sound tab. ```{image} images/image_GA5kbS1gCok0zcxmw8acDga1nbe.webp :width: 1040px :height: 649px :align: center ``` In this panel, you will see: - Output Device: The dropdown menu lists speaker, external headset, and Bluetooth devices. - Input Device: The dropdown menu lists the built-in mic (onboard microphone) and headset input (headset microphone). - Output Volume / Input Volume: Sliders to control playback and recording gain respectively. > Note: The current headphone jack on the development board is a 4-pin connector. The headset insertion detection pin is not routed to the external interface, so the headset is in the default "plugged-in" state. Currently, audio devices such as headphone, speaker, and built-in mic coexist. Therefore, you need to switch manually before using audio. --- # External Headset (Headset) Playback and Recording When you connect a standard 3.5mm headset with a microphone via an adapter cable, you need to manually switch the headset input and output. ## Headset Playback 1. Connect the adapter headset. 2. In the Sound settings, under Output Device, manually select headset. ```{image} images/image_DVO0bNGqvoJX6wxpe8Zcdzd5nQx.webp :width: 789px :height: 488px :align: center ``` 3. Play audio; the sound will be output through the headset. ## Headset Recording 1. Connect the adapter headset with a microphone. 2. Under Input Device, switch to headset input. 3. Open the Sound Recorder application; sound will be captured via the microphone on the headset's inline control. ```{image} images/image_HvX5bNYB5osrCexYfwQcDdPonfe.webp :width: 1048px :height: 656px :align: center ``` 4. Start recording: speak into the headset microphone and observe whether the recording level indicator bar is moving. ```{image} images/image_CxrUbfbzuofnuuxpGCYc9roRnJe.webp :width: 1036px :height: 648px :align: center ``` --- # Onboard Microphone (Built-in MIC) Recording The onboard MEMS microphone is the default recording input source and can be used without connecting any external cables. 1. Confirm the device: Open the "Sound" settings, and in the "Input Device" dropdown menu, select built-in mic (or a similarly named onboard audio input). 2. Test recording: Open the Sound Recorder application and click the record button. The sound captured at this time will come from the onboard MIC. 3. Start recording: Speak into the MEMS microphone on the mainboard and observe whether the "Input Volume" level indicator bar below is moving. --- # Speaker (SPK) It is recommended to use a headset for audio testing. To use the SPK for audio playback, you need to connect an external speaker or PA (Power Amplifier) to the SPK_N and SPK_P test points on the development board. The SPK is currently the direct output from the codec without a built-in PA, so connecting a speaker directly will result in relatively low volume. If higher volume is required, an external PA must be connected before the speaker. Switching steps: 1. Correctly connect your speaker to the corresponding test points on the development board. 2. Open Sound settings, and under the Output Device dropdown menu, select speaker to activate the external playback mode. ```{image} images/image_C0SjbJtl3oWzBYxLNXbckLzcnrd.webp :width: 1280px :height: 691px :align: center ``` 3. Play an audio file (e.g., system sounds or music). The sound will be output from the physical device you selected. You can fine-tune the loudness using the "Output Volume" slider. --- # Bluetooth Audio Recording and Playback The SC200U supports Bluetooth 5.0 for connecting Bluetooth headsets or speakers. > Note: Before testing Bluetooth audio functions, please ensure the Bluetooth antenna is correctly connected. ## Pairing and Connection 1. Go to Settings -> Bluetooth, enable Bluetooth, and click "Add Device". 2. Put your Bluetooth headset into pairing mode, and click "Pair" on the detected device in the list. ```{image} images/image_YeZUb9CweoxQoHx8z5ncmE5OnBe.webp :width: 1038px :height: 649px :align: center ``` ## Switching Usage After a successful connection: - In the "Output Device" dropdown menu, select your Bluetooth device name to transmit music/call audio to the Bluetooth headset. - In the "Input Device" dropdown menu, if the Bluetooth headset supports HFP, you can also select its microphone for recording or calls. - To switch back to the onboard speaker, simply re-select speaker in the output device list. ```{image} images/image_QJehbl35fowVUkxgyrccIPr5n0g.webp :width: 870px :height: 576px :align: center ``` --- # Cellular Voice Call Function The M1 supports standard phone calls over the cellular network (4G VoLTE). Under the Debian system, dialing, answering, hanging up, and other operations are performed through the system's pre-installed GNOME Calls application, while audio routing during the call is controlled via the GNOME Sound settings. ## Audio Preparation Before a Call Before making a call, please select the appropriate audio channel in the GNOME Sound settings according to your usage scenario: - Private call: Connect a headset, select headset as the Output Device, and headset input as the Input Device. - Hands-free call: Select speaker as the Output Device, and built-in mic as the Input Device (pay attention to the distance to avoid feedback/howling). ## Making a Call (Calls App) 1. Find and open the pre-installed Calls application in the GNOME application menu. 2. On the main interface of the Calls app, click the dial pad icon and enter the phone number. ```{image} images/image_URQVbD2qCoyb0NxdXCDc37hjnze.webp :width: 1280px :height: 800px :align: center ``` 3. Click the green Call button; the app will automatically dial out over the cellular network. 4. Once the other party answers, you can proceed with the call normally. ```{image} images/image_TlHrbtXdroLcuixtWzEcYs6inQd.webp :width: 1034px :height: 646px :align: center ``` > Note: The dial pad interface in the Calls app may be relatively small, making it difficult to click all digits. You can manually drag the interface to the top of the screen, and the dial pad will display in full screen. ## Answering and Hanging Up - Answering an incoming call: When a call comes in, the Calls app will pop up a notification window. Click the Accept button to answer. - Hanging up: During a call, click the red Hang Up button on the Calls app interface to end the call. ```{image} images/image_Tc2bbFTFAo43SrxOAygcAXPtnLb.webp :width: 643px :height: 616px :align: center ``` --- # Common Issues and Debugging - Calls app cannot recognize the SIM card or modem: Ensure the SIM card is correctly inserted. You can send the AT command AT$QCSIMAPP=? to check if the module is recognized. - No sound during recording: Check whether the "Input Device" is correctly selected (built-in MIC vs. headset MIC), and observe if the level indicator bar is fluctuating. - System does not automatically switch after plugging in the headset: Due to the adapter connection method, automatic preemption may not occur. It is recommended to manually select the output/input device in the "Sound" settings—this is currently the most reliable method. - Bluetooth connected but no sound: Re-select the Bluetooth device in the output device list and ensure the Bluetooth device's own volume is turned up. - PulseAudio service exception: Restart the audio service by executing the following command in the terminal: - bash - systemctl --user restart pulseaudio