49.91 mm x 100.2 mm
You can choose not to use this sensor and use wires to connect your sensors to SPI pins on the board.
The sensor has 4 sensing points. Only two is used to sens voltage and current as in APM & PIXHAWK. However this can be extended by software so that individual cells for 3S batteries are measured or to use the extra ADC pins in other functions.
This module can output PWM signals upto 16 channels.
This IC is used to control LEDs & Buzzer. Each two outputs of the 8 outputs of the IC are wired up together so there are 4 output ports that support high current. OBAL uses only 2 leds not three and a buzzer. So there is an extra port that can be used.
This switch disables PWM output. It is not connected logically to Ardupilot. SO it is not the ARM switch of Ardupilot. It is a switch that disables PWM output by disabling PCA9685 using a chip enable pin.
All I2c & SPI sensors can be added easily to OBAL.
GPS can be connected to Serial-1 pins as they are connected to TX & RX of Raspberry-PI.
Telemetry can be connected via OTG in USB if you ar using Raspberry-Zero. Other Raspberry-PI's already contain multiple USB and can accept multiple GPS & Telemetry.