Components Previously on the PCB

The printed circuit board has many components that have been deemed obsolete and removed. Below is a list of those components, how they worked, and why the were removed.

Components Removed In Spring 2020

Prior to spring 2020, the PCB was designed for use by both CUBike and CUSail, resulting in many parts that were not necessary for the functioning of the bike. In Spring 2020, a major overhaul was started in part to remove many of these unnecessary parts.

Watchdog

The Watchdog is an external timer circuit that assured the Arduino DUE was correctly executing its loop. The Watchdog’s timer was reset each time the DUE successfully completed a loop. However, if the DUE’s loop execution was unsuccessful, the Watchdog’s timer would not be reset, causing an emergency shutdown and preventing damage to the bike’s systems.

The Watchdog connected to the PCB through three pins, labeled WD+DPINS, and an op-amp.

WD+DPINS

Pin Label	Connected To
1	DUE pin 45
2	DUE pin 43
3	Op-Amp pin 1 WDO

Associated Op-Amp

Pin Label	Connected To
1 WDO	WD+DPINS pin 3
2 GND	GND
3 EN	DUE pin 41
4 WDI	DUE pin 42
5 VCC	C35 --> GND

The Watchdog and associated hardware were removed because an unsuccessful loop execution by the DUE was deemed to be an unlikely source of failure.

POT

The POT (Potentiometer) pin-outs is a grouping of pin-out ports that were designed to be used to connect a potentiometer. A potentiometer is an adjustable resistor that provides varying voltages. By keeping the current constant, measuring how much the potentiometer was adjusted allows one to know the voltage. When making the bike, it was debated whether using a potentiometer or an encoder was better for measuring the position of the bike's front wheel. Although the potentiometer is more accurate than the encoder, it was decided that an encoder was to be used because it was easier to work with. Thus, the POT pin-out ports were deemed to be unecessary.

Pin Label	Connected To
1	GND
2	DUE Pin A10
3	3.3 V

Additional Components Only Used by CUSail

Sail Motor

The old PCB contained outputs for the sail motor and bike motor. Since the bike is not a sailboat, the sail motor outputs were removed.

Sail Power

Similar to the sail motor, only the bike power output is necessary.

Xbee Pro

The Xbee Pro was used in conjunction with CUSail's remote controller. The bike uses a different controller.

Other Components

IMU & RS

The IMU (Inertial Measurement Unit) is a sensor used to provide information regarding the bike's current angle and angular rates. The IMU is connected to the board using a six pin-out terminal (figure N). Because the IMU communicates with the DUE using SPI, the pin-out terminal requires MISO, MOSI, and SCK connections to the DUE. The pin-out terminal has a pin called IMU-CS and it is believed to be the designated SS (Slave Select) for the IMU. Additionally, two pins (5V and GND) supplies power to the IMU.

IMU Pin-Out	Terminal Connection
MISO	MISO
MOSI	MOSI
SCK	SCK
IMU-CS	A11
3.3 V	3.3 V
GND	GND

Similarly, the RS communicates to the DUE using SPI and thus requires the same terminals, MISO, MOSI, SCK, and (in this case) RS-CS. The RS is connected to the board through a six pin-out terminal, two terminals being GND and 3.3V. Initially, the RS terminal was used for the BeagleBone Black that is a micro-controller. The motivation behind the BeagleBone was that the DUE would communicate with the IMU through the BeagleBone. However, the BeagleBone is no longer used and the DUE directly communicates with the IMU directly via SPI. Currently, the pin-put terminal for RS is not used but serves as an extra SPI communication port and thus may be used for any future microcontrollers or peripherals (e.g. Raspberry Pi).

RS Pin-Out	Terminal Connection
MISO	MISO
MOSI	MOSI
SCK	SCK
IMU-CS	Pin 52
3.3 V	3.3 V
GND	GND

Design Changes for IMU & RS

Because the IMU is a critical component for developing an autonomous bicycle and is a sensor that needs to be read periodically and requires initialization, the current implementation of the IMU is going to be remained unchanged. Since the RS terminal is not being used but can be useful for any future implementation of micro-controllers or peripherals that require SPI, the RS pin-out terminal is also remain unchanged.