## Wireless MCU / BLE

Use:

**u-blox NINA-B306-01B**

Open-CPU Bluetooth Low Energy module based on Nordic Semiconductor nRF52840.

Prefer this module because it is:

* actively available from major distributors
* globally pre-certified
* based on the widely supported nRF52840
* equipped with an integrated PCB antenna
* capable of running the complete application firmware directly
* equipped with native USB
* equipped with sufficient SPI, I2C, ADC and GPIO resources

Key resources:

* 1 MB Flash
* 256 KB RAM
* Arm Cortex-M4F at 64 MHz
* BLE 5
* USB device interface
* 3 SPI peripherals
* 2 I2C/TWI peripherals
* 8 ADC inputs
* integrated antenna

Use approximately:

SPI bus 1:
ADS131M08 only

SPI bus 2:
soldered embedded SD/storage only

SPI bus 3:
reserve for expansion or high-speed sensor

I2C bus 1:
BMI270
BMM350
BQ25155

I2C bus 2:
external sensor expansion connector

USB:
USB-C D+ / D-

ADC:
reserve at least two ADC-capable pins for external analog sensors.

Expose SWD programming/debug pads.

Follow the complete u-blox NINA-B306 antenna keepout and ground-plane requirements.

Place the module at a PCB edge with its PCB antenna facing away from:

* LiPo battery
* ground planes within the antenna keepout
* ADS131M08
* EEG electrode traces
* DC/DC inductor
* metallic enclosure parts

Do not place components or copper in the module antenna keepout region.

Use the module as the sole main MCU; do not add a separate application MCU unless later processing requirements prove that it is necessary.