EMBEDDED SYSTEMS BASICS WORKSHOP by ELC Skyward SKYWARD EXPERIMENTAL ROCKETRY
SKYWARD EXPERIMENTAL ROCKETRY Who we are? SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS 2
Our Purpose Skyward Experimental Rocketry is an active student association operating inside Politecnico di Milano, it was born in 2012 with the ambitious goal of designing and realizing small and medium sized experimental sounding rockets. Our project takes on from the passion of its founders and their desire to challenge other similar associations active in Europe. The context we are in is very competitive and stimulating: our goal is to beat the altitude record achieved by an experimental rocket (32300m – HyEND – University of Stuttgart, Germany), and to do this we are following a program divided in different steps, each one involving new development and technological solutions. 3 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Our Workgroup: ELS The electronic system has been designed and assembled entirely within the association, and will handle real-time recording and transmission of data during launch. The electronic system consists of a motherboard, which will coordinate all subsystems, each of which is controlled by a series of dedicated daughter-boards. The firmware on the microprocessors has been developed by our software engineers and it is designed to make the most of the hardware redundancy present onboard. 4 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Distributed System The whole system has been designed in the aim of modularity and flexibility. Anakin Board Stormtrooper Array SKYWARD EXPERIMENTAL ROCKETRY ROCKSANNE 2-ALPHA 5
Distributed System - Flowgraph 6 SKYWARD EXPERIMENTAL ROCKETRY ROCKSANNE 2-ALPHA
PHASE 0: BASICS What is an embedded system? SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS 7
Why Embedded Systems ? LCD GPS HW / SW for Special Purpose ● Optimized for specific tasks ○ Sensors/ Microprocessor/ Actuators ○ IMU ALARM Specific Constraints ● MOTORS Real Time / High Efficiency ○ Failsafe ○ GPS Power Consumption ○ Structural ○ IMU LEDS 8 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Embedded System - Nosecone Array ACTUATORS SENSORS GSM PRESSURE THERMAL CUTTER GPS TEMPERATURE CORE SYSTEM STRAIN GAUGES POWER SYSTEM 9 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Our Design Purpose - Air Conditioning System SENSORS ACTUATORS MICROCONTROLLER 10 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
PHASE I : SPECIFICATIONS Let’s define the proper hardware SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS 11
Our Requirements TEMPERATURE HUMIDITY FSR 0 - 40 [°C] 0 - 100 [%] RESOLUTION 1 [°C] 1 [%] ACCURACY 2 [°C] 5 [%] SAMPLING FREQUENCY 0.1 [Hz] 0.1 [Hz] 12 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Sensors Parameters TRANSDUCER PROPERTIES Range ● Sensitivity ● Resolution ● Accuracy ● Response time ● Precision ● Offset / Linearity / Hysteresis / Dynamic Linearity ● 13 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
LM75 - temperature sensors (125-(-55)) / 2^9 = 0.35 [°C] 1/300ms = 3.33 Hz 14 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Sensors - Other Parameters Supply Voltage (and current consumption) ● Connectivity (Analog or I2C/SPI/UART) ● Package ● 15 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Sensor Connectivity - Digital Busses ● UART ● I2C ● SPI 3 or 4 wire 16 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Sensor Connectivity - Analog Front End GAIN + FILTER SENSORS AMUX + ADC 17 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Package - IC SMT: Suface-Mount Technology THT: Through-Hole Technology ● SIP: single in-line DIP ● TQFP = thin-quad flat pack ● SOIC: Small outline IC Lead pitch: 1inch = 2.54mm ( p about 0.5mm) 0.050 inch (1.27mm) ● BGA: Ball Grid Array ● QFN: Quad Flat No-leads ● TSSOP: thin-shrink small outline package (pitch < 0.050 inch) 18 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Package - others SMT: Suface-Mount Technology THT: Through-Hole Technology 19 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
BME 280 - Humidity parameters 20 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
BME280 - Electric Parameters 21 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Microcontroller - PIC18F26K22 22 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
PHASE II : SCHEMATICS DESIGN Let’s connect all the components SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS 23
Power Section - RT9080 ● LDO: Low Dropout Voltage ● Fixed Output / Adjustable RT9080: ● Vout Fixed: 3.3V ● MAX Input Voltage Range: 1.5V - 5.5V 24 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Other Voltage Regulator - DC:DC converter LDO DC:DC Accuracy High Low Linearity High Noisy Efficiency P = Iout (Vin-Vout) 80 - 95 % 25 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Oscillator Uses the mechanical resonance of a vibrating ● crystal to create an electrical signal with precise frequency External / Built-in ● Special Layout needed ● 26 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Decoupling\Bypass Capacitors Transient in current drawn by a particular ● device, decoupling capacitors provide a local source of charge so that current can be supplied quickly without causing the voltage on the power pins to dip suddenly. These capacitors are connected between ● power and ground to help stabilize the voltage delivered to active digital devices.. 27 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Backup Capacitors 28 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Pull-up/Pull-down Resistors An old wise man once told us: "I've never saw a resistor being afflicted by segmentation fault" Ensure the right logic level even if the ● devices are in Hi-Z state or disconnected 29 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
ICSP Headers - connectors USB POWER MAIN POWER RS485 THERMOCOUPLES STRAIN GAUGES GENERAL PURPOSE 30 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
(many) LEDS 31 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
PHASE II : PCB DESIGN Let’s define where to place these components SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS 32
PCB: Printed Circuit Board Make the electrical interconnections between ● components Mechanical Supports for components ● Many layers: ● Metal (signal and power) ○ Dielectrics (separation) ○ 33 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
PCB REALIZATION With Altium Designer 16 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS 34
What we will see... Components Library Schematics PCB Design 35 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Mask Realization 36 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Etching 37 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
PHASE V : FIRMWARE Quick overview of Real Time Mission Critical Software SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS 38
Real Time Mission Critical Software RealTime: Mission Critical: software which fails if a timing deadline is software whose failure might cause not met. catastrophic consequences (death, damage to property, financial losses, etc.) Digital audio system ● Medical radiation device ● Control application ● Nuclear reactor safety system ● 39 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Real Time Mission Critical Software + RealTime Mission Critical = 40 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Real Time Mission Critical Software ● Car’s airbags ● Space and Aviation navigation system ● Military applications 41 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Real Time Mission Critical Software A control software for a Nuclear Power Plan need to ● sample the temperature of the core and maintain it at the required set point. The temperature may be sampled at fixed ratio and ● need to be processed as soon as possible. Many other sensor need to be monitored in order to ● discriminate False Positive and Real Emergencies. ● Redundancy are even in software for example different ● control algorithm to perform the calculation and a voting system to thrust the results. 42 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Software Development Methodology AGILE 43 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Software Development Methodology AGILE 44 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Software Development Methodology Agile doesn’t fit very well for this ● All requirements need to be covered ● Usually is not possible or not safe to ● patch a released system 45 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
Software Development Methodology 46 SKYWARD EXPERIMENTAL ROCKETRY EMBEDDED SYSTEM BASICS
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