vaguebrownfox01/pnoi-ble_peri

Peripheral program for Pnoi-phone hardware: ESP32

pnoi-ble_peri's Issues

research and select components for digitalizing stethoscope

Component Selection

Component research and selection process for the Pnoi-phone hardware development project.

Requirements:

• Microphones to capture sound simultaneously from two sources
• Development board for recording and wireless transmission (Bluetooth/ wifi)

Phase 1

Microphone

• Condenser microphone with 3.5mm jack: analog sound signal output
• Sound card: convert the analog signal to digital output

Readily available components for prototype development

Development Board

• Raspberry Pi 3B: 1.4GHz 64-bit quad-core processor, dual-band wireless LAN, Bluetooth 4.2/BLE

Powerful processor; easy to set up and program

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Phase 2

Microphone

• MEMS microphone: by Adafruit

Digital output in I2S protocol

Development Board

• Raspberry Pi Zero W: quad-core 64-bit ARM Cortex-A53 processor clocked at 1GHz and 512MB of SDRAM; Bluetooth 4.2, Bluetooth Low Energy (BLE), onboard antenna; I2S Audio

smaller size ( 65mm × 30mm ) and powerful

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Phase 3

Microphone

• MEMS microphone: by Adafruit

Digital output in I2S protocol

Development Board

• Adafruit HUZZAH32: 240 MHz dual core Tensilica LX6 microcontroller with 600 DMIPS; Integrated dual mode Bluetooth (classic and BLE); 2 x I2S Audio; SD-card interface support

more advanced and compact board, energy efficient and suitable for the required function

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pnoi-phone hardware design: latest

design pnoi-steth piece

design pnoi-mouth piece

pnoi-phone hw components: latest

Microphone

• MEMS microphone: by Adafruit

Digital output in I2S protocol

Development Board

• Adafruit HUZZAH32: 240 MHz dual core Tensilica LX6 microcontroller with 600 DMIPS; Integrated dual mode Bluetooth (classic and BLE); 2 x I2S Audio; SD-card interface support

more advanced and compact board, energy efficient and suitable for the required function

breadboard prototype for simultaneous audio recording

Breadboard prototypes

Testing basic functionalities on a breadboard

Functions:

• Simultaneously record from two microphones
• Wirelessly control to Start and Stop recording
• Trasmitt recorded data wirelessly for storage

Phase 1

RPi-3B version

Two electret condenser microphones were employed for sound capture, while sound cards were utilized to convert analog signals into digital format. Simultaneously, the Raspberry Pi records the digital signal through sound drivers (Linux 'arecord'). The Raspberry Pi is programmed to establish a Bluetooth connection with the Pnoi-phone app. This app serves the purpose of initiating and terminating the recording function on the Raspberry Pi. Subsequently, the recorded data is transferred to the app once the recording process is halted.

Problems:

• A lot static of noise was observed from the condenser microphone
• The setup is bulky and not easy for encapsulation
• It also consumes a lot of power and gets hot
• Data transfer of raw audio files in bulk is slow

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Phase 2

Rpi-Zero version

To address prior issues, two MEMS microphones were selected. These microphones feature built-in audio digitization, reducing noise susceptibility. The digital audio data follows the I2S protocol. Raspberry Pi Zero W, a smaller and more power-efficient board, offers comparable performance to the RPi 3B+.

Problems:

• RPi zero is still pretty heavy for the task and possesses many unused features
• Bluetooth audio streaming

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Phase 3

ESP32 version

The MEMS microphone delivered excellent recording quality. To address limitations with the RPi Zero, the ESP32 Feather Board was selected as the development board. Its compact size and lower power consumption, combined with the necessary features, made it the optimal choice.

Problems:

• Bluetooth Audio Protocol