First prototype boards arrived this week. 

In the weekend I did basic tests of all the subsystems:

• Charger/regulator. Voltage levels
• Microphone+amp. Gain, noise
• Microcontroller. Flashing, toggle GPIO pin - BLE module. I2C communication.
• Accelerometer. I2C communication
• LEDs. Blink

As always with a first revision, there are some issues here and there. But thankfully all of them have usable workarounds. So we can develop with this board.

Examples of issues identified:

• LEDs are mounted the wrong way. Flip them or use external pins on header
• Battery charger 4.2v is too high for BLE module and MEMS mic. Use external 3.3v regulator
• MEMS mic did not work. Use external elecret mic

Next step will be to write some more firmware to validate more in detail that the board is functional. This includes:

• Driver for Holtek BC7161 BLE module (I2C)
• Driver for ST LIS3DH accelerometer (I2C)
• ADC readout for audio input