Arduino-Timer-Conflicts-Considerations

Arduino-Timer-Conflicts-Considerations

NOTES for Dr. Bear:

https://code.google.com/p/arduino/wiki/HardwareResourceMap (From Arduino)
http://forum.arduino.cc/index.php/topic,21975.0.html (Possible alternate servo library)
http://forum.arduino.cc/index.php/topic,21975.0.html (ServoTimer2 Inf)
http://letsmakerobots.com/node/35314 (discussion of Ultrasonic conflicts)
http://forum.arduino.cc/index.php?topic=106043.msg1312639#msg1312639 (Fix for NewPing?)


This is the Very Beginning of documenting the Arduino Timers, Timer Conflicts, solutions and other considerations. Several people on the Arduino forums are contributing to this (Discussion HERE).

Anyone who has something to contribute or correct:

• JOIN the WIKI and edit, or
• Email stuff to terry@yourduino.com

ARDUINO RESOURCES THAT NEED TO BE MANAGED

1. Hardware Timers (0,1,2 on Arduino UNO, Duemilanove, etc)
2. SKETCH Memory:
   1. FLASH (Sketch code space)
   2. RAM (Sketch variable space, stack etc)
   3. EPROM (NonVolatile Memory)
3. I/O Pins
4. PROTOCOL-SPECIFIC:
   1. SPI CS pin
   2. SPI Mode
   3. I2C Device Addresses
   4. I2C (?Speed?)
5. INTERRUPT DISABLE DURATION
6. ?
7. ?
8. ?

QUESTIONS TO ASK OF LIBRARY CONTRIBUTORS??

1. What Timer(s) Does the library use?
   1. Does it change the Timer Mode or Frequency?
2. If it uses SPI:
   1. What pin is used for CS?
   2. Can the CS pin be changed? How?
3. If it uses I2C
   1. What device addresses are used?
   2. Are there I2C Speed considerations?
4. ?
5. ?
6. ?

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STANDARD ARDUINO LIBRARIES

LIBRARY NAME

LIBRARY FUNCTION

TIMER(S) USED

EEPROM

reading and writing to"permanent" storage

Ethernet

for connecting to the internet using the Arduino Ethernet Shield

Firmata

for communicating with applications on the computer using a standard serial protocol.

GSM

for connecting to a GSM/GRPS network with the GSM shield.

LiquidCrystal

for controlling liquid crystal displays (LCDs)

SD

for reading and writing SD cards

Servo

for controlling servo motors

SPI

for communicating with devices using the Serial Peripheral Interface (SPI) Bus

SoftwareSerial

for serial communication on any digital pins. Version 1.0 and later of Arduino incorporate Mikal Hart's NewSoftSerial library as SoftwareSerial.

Stepper

for controlling stepper motors

TFT

for drawing text , images, and shapes on the Arduino TFT screen

WiFi

for connecting to the internet using the Arduino WiFi shield

Wire

Two Wire Interface (TWI/I2C) for sending and receiving data over a net of devices or sensors.

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TABLE of Arduino Supplied Libraries use of Timers:

Arduino Library	Timer Used	/*---( Comments )---*/	Alternatives
delay,millis, micros	0
PWM Pins 5, 6	0
Servo	1
PWM Pins 9,10	1
PWM Pins 3,11	2
Tone	?

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FROM  https://code.google.com/p/arduino/wiki/HardwareResourceMap
 
 

Global timer settings

• TIMER0, TIMER1, TIMER2: prescale factor = 64
• On all chips other than ATMEGA8: TIMER0 in fast PWM mode
• TIMER1, TIMER2 in 8-bit phase correct PWM mode
• On ATMEGA1280:
  • TIMER3, TIMER4, TIMER5 prescale factor = 64
  • TIMER3, TIMER4, TIMER5 in 8-bit phase correct PWM mode

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analogWrite();

• Pins 5, 6 uses TIMER0
• Pins 9, 10: uses TIMER1
• Pins 3, 11 uses TIMER2

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millis();

• TIMER0_OVF_vect

micros();

• TIMER0_OVF_vect

delay();

• TIMER0_OVF_vect (via millis())

delayMicroseconds();

• Turns off all interrupts while it's running

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ARDUINO LIBRARY RESOURCES:
 Liquid Crystal:
 

• Uses delayMicroseconds() in most functions, so will disable interrupts frequently

Servo:

• ATMEGA8, 168, 328:
  • Uses TIMER1_COMPA_vect
  • Sets the prescale factor = 8 (normally = 64)
  • Uses OCR1A

Software Serial:

• Uses delayMicroseconds() in most functions, so will disable interrupts frequent

Stepper:

• uses TIMER0_OVF_vect via millis() function

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CONTRIBUTED LIBRARY RESOURCES:
 
 

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