AVR8 - Input Capture at ICP1 Pin

#1 · April 18, 2025, 5:22 pm

SimulIDE_1.1.0-R2055_Win32, W7
ATmega8

ACSR
Bit_2 [ACIC]: enables the Input Capture function

TIMSK
Bit_5 [TICIE1]: enables Input Capture Interrupt

TCCR1B
Bit_7 [ICNC1]: Input Capture Noise Canceler for ICP1 input [delayed by four Oscillator cycles]
Bit_6 [ICES1]: Input Capture Edge Select for ICP1 input [0= falling edge, 1= rising edge]

TIFR
Bit_5 [ICF1]: Input Capture Flag [cleared by writing a logic one to its bit location]

============================================================

In the attached code, PowerAC_v1.zip:

ACSR, Bit_2 [ACIC] = 1, the Input Capture function enabled
TIMSK, Bit_5 [TICIE1] = 0, the Input Capture Interrupt disabled
TCCR1B, Bit_7 [ICNC1 = 1, the Input Capture Noise Canceler for ICP1 input enabled
TCCR1B, Bit_6 [ICES1] = 1, the Input Capture Edge Select for ICP1 input [rising edge]
TIFR, Bit_5 [ICF1]: BUG, the Input Capture Flag is not set

Please see in the attached test code:

1961	CHCK_Hz:
1962		SBIS Hz_In ; ICP1
1963		RJMP END_act
1964	
1965		NOP ; [breakpoint is reached when ICP1=high]
1966		NOP
1967		NOP
1968		NOP
1969		NOP
1970		NOP
1971	
1972	; if ICF1=0, goto END_act:
1973		IN r17, TIFR
1974		SBRS r17, ICF1
1975		RJMP END_act
1976	
1977		NOP ; [breakpoint is not reached]

Thank you.
Kerim

Uploaded files:

PowerAC_v1.zip

#2 · April 18, 2025, 8:23 pm

Hi.

I will have a look as soon as possible.

#3 · April 19, 2025, 2:44 am

Quote from arcachofo on April 18, 2025, 8:23 pm

Hi.

I will have a look as soon as possible

Very sorry, by checking again, it seems that the line of ACSR was erased by mistake (that is the Input Capture function is not enabled).

I will restore it and test the code again.

#4 · April 19, 2025, 3:15 am

I restored it:

    LDI   r16, (1<<ACIC)
    OUT   ACSR, r16

But again, ICF1 flag is not set when ICP1 is high.

Uploaded files:

PowerAC_v2.zip

#5 · April 21, 2025, 9:52 am

Seems that IC Unit is not activated in Atmega8.

To fix it open file: data/AVR/mega8/mega8_perif.xml
And add this line in Timer1:

<icunit name="IC1"  pin="PORTB0" icreg="ICR1L,ICR1H"   bits="ICES1,ICNC1"   interrupt="T1CAP" />

It should look like this:

  <timer name="TIMER1"  type="160" configregsA="TCCR1A" configregsB="TCCR1B"
                        counter="TCNT1L,TCNT1H"
                        clockpin="PORTD5"
                        interrupt="T1_OVF"
                        prescalers="0,1,8,64,256,1024,EXT_F,EXT_R" 
                        prselect="CS10,CS11,CS12" >
    
    <ocunit name="OC1A" pin="PORTB1" ocreg="OCR1AL,OCR1AH" bits="COM1A0,COM1A1" interrupt="T1COA" />
    <ocunit name="OC1B" pin="PORTB2" ocreg="OCR1BL,OCR1BH" bits="COM1B0,COM1B1" interrupt="T1COB" />
    <icunit name="IC1"  pin="PORTB0" icreg="ICR1L,ICR1H"   bits="ICES1,ICNC1"   interrupt="T1CAP" />
  </timer>

KerimF has reacted to this post.

#6 · April 22, 2025, 4:05 am

Thank you.

#7 · May 28, 2025, 12:20 pm

SimulIDE_1.1.0-R2069_Win32, W7
ATmega8

I am very sorry. Only now, while working on a new project/code, I discovered that I was wrong from the beginning about ACIC flag.

ACSR
Bit_2 [ACIC]: enables the Input Capture function via ICP1 or ACO (the comparator output).

Actually, ACIC=0, not 1, to enable the Input Capture at ICP1 pin.