PIC microcontroller program in ASM

[aceMan]

Hi there.
Anyone out there used PIC microcontroller b4?? Especially 16F877.
I am using it to count frequency. I am using Timer1. I know the routine for initialising. I am also transmitting the received frequency to PC com port. That also I know.

The thing is I wanna know the code for getting the received frequency which is counted into frequency. The received frequency I guess will be as period in TMR1H:TMR1L. From here how am I to transform to frequency??

Can somebody help. Thanks in advance.

[hiran]

give more details.
how u going tio count using timer1

[aceMan]

I am using it as counter mode. I make a delay while turning on the timer. and stop the timer. I bring it into temporary vaiable and this is where the problem. I need to convert to frequency as what I seem to know is it is in period as the timer is counting at every rising edge.

Here is the part of programme:

Main:
clrf T1CON ; Initialize T1 Timer
clrf INTCON
Bank1
clrf PIE1 ; clear interrupt
Bank0
clrf Index ; clear Index
clrf PIR1
movlw 0x02
movwf T1CON
clrf TMR1H
clrf TMR1L
bsf T1CON,TMR1ON
call Delay200mS
bcf T1CON,TMR1ON
call SerialSetup ; whrn returns, still in bank0

again:
clrf TMR1H
clrf TMR1L
bsf T1CON,TMR1ON
call Delay200mS
bcf T1CON,TMR1ON
call GetFreq

GetFreq: movf TMR1H,W
movwf FreqHi
movf TMR1L,W
movwf FreqLo
retlw 0

this is the programme. After GetFreq I dunno how to continue. I might have to use some Math function but seriously dunno how

Thanks

[hiran]

hey aceman!
I think Ur problem is how to calculate the frequency.
now u have the no. of cycles for 200ms, as i understood, in 16 bit TMR1 register.
why dont u make that delay 1 second and get the cyles per second value directly.
or else u have to add the value 5 times to get the frequency.
anyway u can get frequency in two 8 bit registers.
I think this is ur problem now.
anyway u can get upto 65536 x 5 Hz if u use 200ms duration. this is some 300kHz.
for conversion check the attached B2BCD routine.
i used it to convert hex data into bcd for a display driver.



B2BCD MOVLW 0x08
MOVWF BIT ;stores the current bit position
CLRF DIG1
CLRF DIG2
ROTATE RRF VALUE,F
BTFSC STATUS, C
CALL ADD
DECFSZ BIT,F
GOTO ROTATE
RETURN

ADD MOVF BIT,W
CALL LOOKUP
MOVWF INCVAL
INCDIG1 INCF DIG1,F
BTFSC DIG1,3
CALL CHKDIG1
DECFSZ INCVAL,F
GOTO INCDIG1
RETURN

LOOKUP ADDWF PCL,F
NOP
RETLW 0x80
RETLW 0x40
RETLW 0x20
RETLW 0x10
RETLW 0x08
RETLW 0x04
RETLW 0x02
RETLW 0x01

CHKDIG1 BTFSC DIG1,1
CALL INCDIG2
RETURN

INCDIG2 CLRF DIG1
INCF DIG2,F
BTFSC DIG2,3
CALL CLRDIG2
RETURN


this is to control 8 bit value. u can use 2 lookup tables and with slight modifications u can do ur job.

[aceMan]

Hi hiran,
thanks for your advice.
I will try changing to 1 s delay and also use the B2BCD.

I will let you know of any progress or trouble as soon as possible.

If I havent tell u. I am uing this for speed detector. I have to use th doppler input and then convert to speed and pump it out to the serialport.

Thx
aceMan