Timers¶

Timer hardware¶

The ATmega128 has 4 timers/counters:

TC name	Bits	# Output compare registers	# Output compare pins
TC0	8	1	1
TC1	16	3	3 (one shared with TC2)
TC2	8	1	1 (shared with TC1)
TC3	16	3	3

All timers support:

• Overflow and compare match interrupts
• Clear timer on compare match (Auto reload, CTC)
• Phase correct PWM
• Fast PWM

Dragonfly timer pin connections¶

Pin function	Pin name	Alternate functions	Net name	Function	Comments
OC0	PB4	--	!IR_EN	Rangefinders power switch
OC1A	PB5	--	PWM_HB1	Motor
OC1B	PB6	--	PWM_HB1	Motor
OC1C/OC2	PB7	--	PWM_BUZZ	Da Beep
OC3A	PE3	AIN1	DIO1	DIO pin 3	Analog comperator
OC3B	PE4	INT4	DIO2/SCL_B	DIO pin 5	External Interrupt
OC3C	PE5	INT5	DIO3/SDA_B	DIO pin 7	External Interrupt

Timer to function allocation¶

Functions:

• Motors
• Buzzer
• Orbs
• Time base

• The motors have to use TC1, because they are connected to OC1A/OC1B (and hardware PWM should be used).
• The Buzzer has to use TC2 because it is connected to OC2 (and hardware frequency generation should be used).
• The orbs cannot be shared with the motors because the motors (hardware PWM) require a PWM mode of the time, while the orbs (software PWM) require a non-PWM mode to allow for immediate OCR update (this is due to the implementation of the AVR timer modes)

Current plan:

Function	Timer
Motors	TC1
Buzzer	TC2
Time base
Orbs	TC0

Timer Uses (Old)¶

Timer 1	motor.c
Timer 2	buzzer.c (odometry also seems to use this)
Timer 3	time.c, orb.c