a microcontroller system AT89c2051 and an LCD display we can create a digital frequency counter which can measure frequencies up to 250KHz. LCD is used LM16200.
LM16200 LDC Pic
Pin LCD LM16200
Scheme of frequency counter digital using AT89c2051 are as follows:
AT89c2051 to program, we use the Bascom 8051, the following programs Frequency caunter Digital Using AT89c2051:
'--------------------------------------------------------
' file: efy20fm24.BAS 25-12-05
' Frequency Meter Program using AT89c2051 micro controller
' written using bascom-51 from www.mcselec.com holland
' an embedded visual basic compiler for 8051 micro
' controllers
' by K.S.Sankar Web: www.mostek.biz
'------------------------------------------------------
' Connect the timer0 input P3.4 to a frequency generator
' with 24 mhz xtal accuracy ok upto 250khz
' define crystal speed and include file
$regfile = "89c2051.dat"
$crystal = 24000000
' define variables used
Dim A As Byte
Dim C As Long , D As Long
Dim Count As Word
Dim T0ic As Long
Dim Delayword As Word
' Initialize variables
Count = 0
T0ic = 0
D = 0
' initialize ports
P1 = 0
P3 = 255
' configure lcd display
Config Lcd = 16 * 2
Config Lcdpin = Pin , Db4 = P1.4 , Db5 = P1.5 , Db6 = P1.6 , Db7 = P1.7 , E = P1.3 , Rs = P1.2
Cls
'clear the LCD display
Lcd " EFY Freq Meter "
' define timer0
Config Timer0 = Counter , Gate = Internal , Mode = 1
'Timer0 = counter : timer0 operates as a counter
'Gate = Internal : no external gate control
'Mode = 1 : 16-bit counter
' set t0 internal interrupt
On Timer0 Timer_0_overflow_int
' interrupt will be generated on every 65536 count
Priority Set Timer0
Enable Interrupts
Enable Timer0
Counter0 = 0
'clear counter
Start Counter0
'enable the counter to count
Do
'set up a 1 sec accurate DO NOTHING loop
Enable Interrupts
'wait 1 as per BASCOM-51 is not accurate
For Delayword = 1 To 45440
Next Delayword
Disable Interrupts
C = Counter0
'get counter value
D = T0ic * 65536
Lowerline
C = C + D
T0ic = 0
Lcd " "
Lowerline
' show the frequency
Lcd "f=" ; C ; " Hz"
Waitms 255
Waitms 255
C = 0
Counter0 = 0
Start Counter0
're-start it because it was stopped by accessing the COUNTER
Loop
' timer0 int subroutine
Timer_0_overflow_int:
Rem timer0 overflow ( 65535 ) interrupt comes here
' increment the variable
Incr T0ic
Return
End
' end of program
' uses 1106 bytes of program memory
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