Arduino Rapid Prototyping with Python, C++ and Web Services

Arduino Rapid Prototyping
with Python, C++ and Web Services
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Robert Smallshire @robsmallshire
Friday, 16 November, 12

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Norway

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Arduino Out of the Box
An introduction to Arduino hardware and development
Behind the Scenes
Understanding how Arduino works and using professional tools
Developing with Web Services
Application architectures to ease Arduino prototyping
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ATmega328P
ATmega16U2
power
regulation
serial
I/O
16 MHz
crystal

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8271ES–AVR–07/2012
Features
• High Performance, Low Power Atmel®AVR® 8-Bit Microcontroller Family
• Advanced RISC Architecture
– 131 Powerful Instructions – Most Single Clock Cycle Execution
– 32 x 8 General Purpose Working Registers
– Fully Static Operation
– Up to 20 MIPS Throughput at 20MHz
– On-chip 2-cycle Multiplier
• High Endurance Non-volatile Memory Segments
– 4/8/16/32KBytes of In-System Self-Programmable Flash program memory
– 256/512/512/1KBytes EEPROM
– 512/1K/1K/2KBytes Internal SRAM
– Write/Erase Cycles: 10,000 Flash/100,000 EEPROM
– Data retention: 20 years at 85qC/100 years at 25qC(1)
– Optional Boot Code Section with Independent Lock Bits
In-System Programming by On-chip Boot Program
True Read-While-Write Operation
– Programming Lock for Software Security
• Atmel® QTouch® library support
– Capacitive touch buttons, sliders and wheels
– QTouch and QMatrix® acquisition
– Up to 64 sense channels
• Peripheral Features
– Two 8-bit Timer/Counters with Separate Prescaler and Compare Mode
– One 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode
– Real Time Counter with Separate Oscillator
– Six PWM Channels
– 8-channel 10-bit ADC in TQFP and QFN/MLF package
Temperature Measurement
– 6-channel 10-bit ADC in PDIP Package
Temperature Measurement
– Programmable Serial USART
– Master/Slave SPI Serial Interface
– Byte-oriented 2-wire Serial Interface (Philips I2C compatible)
– Programmable Watchdog Timer with Separate On-chip Oscillator
– On-chip Analog Comparator
– Interrupt and Wake-up on Pin Change
• Special Microcontroller Features
– Power-on Reset and Programmable Brown-out Detection
– Internal Calibrated Oscillator
– External and Internal Interrupt Sources
– Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, Standby, and
Extended Standby
Atmel 8-bit Microcontroller with 4/8/16/32KBytes In-
System Programmable Flash
ATmega48A; ATmega48PA; ATmega88A; ATmega88PA;
ATmega168A; ATmega168PA; ATmega328; ATmega328P
SUMMARY • 32768 bytes ﬂash
• bootloader
• program
• const static data†
• 2048 bytes EEPROM
• persistent data
• 2048 bytes SRAM
• stack
• static
• heap‡
† If you know what you’re doing
‡ A luxury you can’t afford

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The Arduino programming
language: “Wiring”

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Many neat shields on the market
Arduino Shields
‣ Many neat
shields on the
market
‣ Easy to fabricate
your own using
protoshields or
PCB production
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Oh dear!
Arduino Shields ‣ Shield physical design
is incredibly dumb
‣ Most shields are badly
designed, amateurish
and mutually
incompatible
‣ Getting some shields to
work on the Mega
requires hardware
modiﬁcation (better
with Arduino R3)
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Behind the Scenes
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avr-gcc
avr-libc
avrdude
http://www.nongnu.org/avr-libc/
Arduino.h
Wire
Serial
SPI
Ethernet
SD
EEPROM
“Libraries”
Arduino
bootloader
Arduino
IDE
core.a
avr-ar
blink.ino
blink.cpp
avr-objcopy
blink.cpp.o
SPI.cpp.o
blink.cpp.elf
blink.cpp.hex
blink binary
make

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Removing the training wheels
‣ Eclipse IDE with CDT (C/C++ integration)
• Arduino plugin : Higher level
http://eclipse.baeyens.it/
• AVR plugin : Lower level
http://avr-eclipse.sourceforge.net/wiki/index.php/The_AVR_Eclipse_Plugin
‣ arscons - SCons builds for Arduino
• https://github.com/suapapa/arscons
‣ AVR Freaks - Arduino-free AVR programming in
C, C++, assembler
• http://www.avrfreaks.net/
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Beyond the Arduino IDE

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Expect to be tripped up by this stuff
Gotchas
‣ Different Arduino models (Uno / Mega) use
different programmers “Arduino” versus
“Atmel STK500 Version 2.0 ﬁrmware”
‣ Arduino community is (mostly) a bunch of
amateurs with little experience of ‘real’
programming. Lots of bad information and
unfounded hearsay. Mythology.
‣ Some C++ features rely on ‘missing’ pieces of
libc (such as pure virtual functions)
• extern "C" void __cxa_pure_virtual(void)
{ while(1); }
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Behind the Scenes
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2
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HTTP

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WiFi shields

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Other Arduino web services
‣ RESTduino
• http://jasongullickson.posterous.com/restduino-arduino-hacking-for-the-rest-of-us
• low level pin access (digitalWrite, analogRead)
• badly named - it’s not RESTful at all (no HATEOAS, no HTTP verbs)
‣ Teleduino
• https://www.teleduino.org/
• Allows access to Arduino over the Internet (not just the network) via their centralised
server.
• low level pin access (digitalWrite, analogRead)

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Arduino Mega 2560
Arduino Ethernet &
SD Card Shield
Prototype Shield
(PIC16F77 as servo
controller)
MAX6651 shield
MAX6651 shield
I2C bus
SPI bus
Linux laptop
Ethernet
Dallas One Wire bus
H%
Proprietary One
Wire Bus
Server cabinet
environment
controller

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Arduino Rapid Prototyping with Python, C++ and Web Services

Arduino Rapid Prototyping with Python, C++ and Web Services

Robert Smallshire

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