Networked CAN Bus Controller - UTC Aerospace Team 1907: Matthew Cox, Pawel Bezubik, John Nguyen Advisor: Dr. Chandy Sponsor: Chris Soumakis, William Villano, Chris Grant
Project Outline Design a CAN Bus controller ● for an aerospace PCI rack. Allows for distributed ● control and sensing of multiple devices. Create an interactive sensor ● network using multiple nodes.
Sponsor Requirements - General Overview Design a controller to control and monitor different types of I/O such as sensors, switches, ● motors and valves Utilize CAN bus for communication between devices and design a protocol on top of CAN ● to relay information between devices. Design a PCB that fits the VITA 20 Standard Single Width Form Factor for PCI Mezzanine ● Cards (PMC).
Progress ● MCU dev board arrived and setup ● CAN Bus software demo completed ○ Send and receive functions ○ CAN interrupt handler ● Finalizing software architecture ● Writing test code for peripherals ● Working on circuit design and analysis
ATSAMC21J18A Provides most flexibility in terms of Serial I/O ● True 5V tolerant ARM Microcontroller ● On-board CAN Controller with superior features: ● 64 dedicated receive buffers ○ 32 dedicated transmit buffers ○ 2 configurable receive FIFOS ○ Comprehensive set of peripherals and features ● Best benefits for unit cost ●
Software High Level Start at CAN message ● Message from CAN decides ● function of MCU Emergency Flags can also be ● interrupts
Software Polling Variable Timer controls polling interval ● time Continuous input from sensors ● Faster access to sensor data ●
CAN Network Protocol Data Bits Function ID[28:26] Priority Level ID[25:18] Transmit Device ID ID[17:9] Receive Device ID ID[8:4] Packet Type ID[3:0] Command
Discrete Interface ● 2-3 required on board ● Convert voltage range to discrete input ● Scale circuit to 10mA when switch closes ● Analyzing 2 options
Discrete Input - First option ● Early Design of Current Threshold Circuit ● Schottky diode to reduce output swing to minimize slew rate ● Zener diode for reference voltage ● Inverting input will be slightly above/below ground
Discrete Input - Second option ● Current shunt resistor + Differential Current Sense Amplifier IC ● Allows for current to be measured as a voltage based on shunt value ● Can allow for variable current threshold defined in software
Analog Interface ● Unity gain amplifier ● 0-10V inputs to be utilized for various sensors ● 5 Inputs required on board ● Buffer and scale voltages down to 0-5V ● Read into MCU
Current Driver ● Used to drive a coil and create a deflection/holding torque ● Requires an accurate current source up to 200mA ● Controlled by ~22 kHz PWM command. ● Example circuit withheld by sponsor due to use of company IP
PCB Form Factor ● Layout according to VITA 20 Standard ● Specification is for PCI Mezzanine Cards (PMC) ● Board will be secured into enclosure with other cards ● We will be utilizing Single Width specification size: 143.75mm x 74mm
Budget ● Sponsor has no Items Quantity Price set development MCU Dev Kit - 1 $52.49 budget ATSAMC21J18A
Timeline ● Finish I/O circuit designs by 12/22/18 ● Peripheral test code completed by 12/22/18 ● Breadboard Testing: 12/30/18 - 1/21/19 ● Design Revisions / Prototype PCB: 1/22/19 - 2/21/19 ● Test first PCB: 2/22/19 - 3/4/19 ● PCB Revisions / Corrections: 3/5/19 - 4/1/19 ● Final Testing / Extra Time: 4/2/19 - 4/22/19 ● Final Report: 4/22/19 - 4/29/18
Thank You We look forward to continuing our design. Any feedback is much appreciated. Questions??
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