How To Build A Better Arduino

How to Build a Better Arduino – the Development of MHVlib
Alastair D’Silva
@EvilDeece
http://alastair.d-silva.org
http://www.makehackvoid.com

What is an Arduino
A hardware and software platform for prototyping electronics
Low entry barrier allows programmers to interact with the real world
Built on top of Wiring

Love Arduino
Cheap hardware
Simple to understand
Serial bootloader makes programming easy

Hate Arduino
Slow
Memory inefficient
Caused by:
Excessing handholding
Backwards compatibility

Fix Arduino
Keep the good parts
Hardware
Bootloader
Ditch the bad parts
Runtime libraries

Design Philosophy
Portable (support all ATMEGA & ATTINY)
Lean
Memory efficient
Use interrupts if possible
No deprecated calls
No warnings

HardwareSerial
Arduino
Uses fixed length, preallocated 128 byte RX buffers
Preinstanties 1 object for each serial port
Reinvents the wheel regarding string formatting
Interrupt driven RX, busy TX
MHVlib
User allocates buffers and passes them in
User instantiates only what is needed
Provides interrupt driven & busy variants of RX/TX
Provides PROGMEM TX support

Digital IO
Arduino
Lots of handholding
Uses extensive tables in PROGMEM to look up pin ports & bits
~55 clocks
MHVlib
No handholding
Uses macros
Single instruction, 2 clocks

MHVlib Digital IO
io.h:
//Dir,Output,Input,Bit
#define MHV_PIN_B0 &DDRB,&PORTB, &PINB,0
#define mhv_pinOn(mhvParms)
do {
_mhv_pinOn(mhvParms)
} while(0)
#define _mhv_pinOn(mhvDir,mhvOutput,mhvInput,mhvBit)
*mhvOutput |= _BV(mhvBit);

Digital IO Usage
Arduino
pinMode(13, OUTPUT);
digitalWrite(13, 1);
MHVlib
mhv_setOutput(MHV_ARDUINO_PIN_13);
mhv_pinOn(MHV_ARDUINO_PIN_13);

Servo Library
Arduino Servo
Consumes 1 16 bit timer per 12 servos
~10 bits of significance
Resolution of 16 clock cycles
ArduinoSoftwareServo
Uses a 16 bit int, valid values are 0 to 180
Refresh must be called periodically
Sorts the list of servo positions on each pass
Lots of busy waiting
MHVlib
Uses a uint16_t, 0-65535 (~14 bits significant)
Consumes 1 16 bit timer
Resolution of 2 clock cycles
No restrictions as to how many servos
Only sorts when positions change

References
http://billgrundmann.wordpress.com/2009/03/03/to-use-or-not-use-writedigital/
http://www.arduino.cc

First (Real) Project
Spindle controller for a CNC Mill
Generates a servo signal to a BLDC controller to drive an RC helicopter motor (up to 1.8kW)
Read from the serial port and set the speed
Monitor the spindle and adjust the speed
Report actual speed back to the PC
Arduino version
11,900 bytes of flash
500 bytes of RAM
MHVlib version
6930 bytes of flash
177 bytes of RAM

http://blog.bricogeek.com	659
http://www.slideshare.net	49
http://translate.googleusercontent.com	1

How To Build A Better Arduino

by AlastairDSilva on Apr 03, 2010

Accessibility

Categories

Tags

Upload Details

Usage Rights

3 Embeds 709

Statistics

How To Build A Better Arduino — Presentation Transcript