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129 lines
3.0 KiB
ArmAsm
129 lines
3.0 KiB
ArmAsm
4 years ago
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/*
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* ----------------------------------------------------------------------------
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* "THE BEER-WARE LICENSE" (Revision 42):
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* Joerg Wunsch wrote this file. As long as you retain this notice you
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* can do whatever you want with this stuff. If we meet some day, and you think
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* this stuff is worth it, you can buy me a beer in return. Joerg Wunsch
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* ----------------------------------------------------------------------------
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*
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* Demo combining C and assembly source files.
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*
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* $Id$
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*/
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/*
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* This file contains the interrupt service routine implementations
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* when compiling the project for the ATtiny13 target.
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*/
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#include <avr/io.h>
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#include "project.h"
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#if defined(__AVR_ATtiny13__)
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/*
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* Timer 0 hit TOP (0xff), i.e. it turns from up-counting
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* into down-counting direction.
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*/
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.global TIM0_COMPA_vect
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TIM0_COMPA_vect:
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in sreg_save, _SFR_IO_ADDR(SREG)
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inc counter_hi
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clr flags
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out _SFR_IO_ADDR(SREG), sreg_save
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reti
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/*
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* Timer 0 hit BOTTOM (0x00), i.e. it turns from down-counting
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* into up-counting direction.
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*/
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.global TIM0_OVF_vect
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TIM0_OVF_vect:
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in sreg_save, _SFR_IO_ADDR(SREG)
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inc counter_hi
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ser flags
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out _SFR_IO_ADDR(SREG), sreg_save
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reti
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;;; one 16-bit word to store our rising edge's timestamp
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.lcomm starttime.0, 2
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.extern pwm_incoming
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.extern intbits
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.global PCINT0_vect
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PCINT0_vect:
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in sreg_save, _SFR_IO_ADDR(SREG)
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;; save our working registers
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push r18
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push r19
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push r20
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push r21
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;; Now that we are ready to fetch the current
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;; value of TCNT0, allow interrupts for a
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;; moment. As the effect of the SEI will be
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;; deferred by one instruction, any possible
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;; rollover of TCNT0 (hitting BOTTOM when
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;; counting down, or MAX when counting up) will
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;; allow the above ISRs to trigger right here,
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;; and update their status, so our combined
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;; 16-bit time from [counter_hi, TCNT0] will
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;; be correct.
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sei
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in r20, _SFR_IO_ADDR(TCNT0)
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cli
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;; Now, make our working copy of the status,
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;; so we can re-enable interrupts again.
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mov r21, counter_hi
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mov r19, flags
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sei
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;; what direction were we counting?
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sbrs r19, 0
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;; we are down-counting, invert TCNT0
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com r20
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;; at this point, r21:20 has our current
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;; 16-bit time
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;; now, look which of the edges triggered
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;; our pin-change interrupt
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sbis _SFR_IO_ADDR(PINB), 4
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rjmp 10f
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;; rising edge detected, just record starttime
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sts (starttime.0) + 1, r21
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sts starttime.0, r20
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rjmp 99f ; we are done here
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;; Falling edge: compute pulse width, store it
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;; into pwm_incoming, disable pin-change
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;; interrupt until the upper layers had a chance
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;; to fetch the result.
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10: in r18, _SFR_IO_ADDR(GIMSK)
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andi r18, ~(1 << PCIE)
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out _SFR_IO_ADDR(GIMSK), r18
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;; pwm_incoming = current_time - starttime
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lds r19, (starttime.0) + 1
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lds r18, starttime.0
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sub r20, r18
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sbc r21, r19
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sts (pwm_incoming) + 1, r21
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sts pwm_incoming, r20
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;; signal upper layer
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lds r18, intbits
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ori r18, 1
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sts intbits, r18
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99:
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pop r21
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pop r20
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pop r19
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pop r18
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out _SFR_IO_ADDR(SREG), sreg_save
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reti
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#endif /* ATtiny13 */
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