PIC Microcontoller Time Methods

Clocks@, Time Standards@, Real Time@ and Delays,

• PIC specific oscillators and delays
• Code generator  for Delays by Nikolai Golovchenko Wow!
• Clocks esp. crystal oscillators@
• Watch Dog Timers@
• Counters and counting. +
• Count seconds, minutes, and hours. by Andrew Warren
• Run a xtal oscillator PIC16f872 to exactly 1000 hertz
• PIC countdown on 4, 7 segment LED's timer 16F84A
• PIC 16F84A elapsed time counter on 4, 7 segment LED's
• PIC long term timer without interrupts
• Timer tutorial (incl prescalers)
• Compinsating for ISR time loss in a time sensitve main code loop
• Converting BCD RTC formats by Drew Vassallo
• NJU6355 E or G version Real Time Clock interface code by Andrew D. Vassallo
• Easy Interrupt sample
• 16F676 Real Time Clock by Edwin Tugano Jr.
• YET ANOTHER TIMER TUTORIAL 18F452 based by John Nall
• High precision timed events without interrupts for 12-bit PIC (instruction cycle accurate) using a non-isochronous main loop +
• High precision timed events without interrupts for 12-bit PIC (instruction cycle accurate) using a non-isochronous main loop (without use of the pcl register) +

From the CHEAPIC tutorial:

• bincnt.asm - Count in binary on 4 LEDs
• swcnt.asm - Count switch closures.
• eggtimer.asm - Countdown timer, displays minutes and 10's of seconds on LEDs
• morsenbr.asm - Send numbers 0-9 out on piezo speaker
• binclock.asm - A clock which displays hours and minutes in BCD on LEDs at keypress
• worktime.asm - Uses a LCD to display a timer that can be started and stopped by pushbutton
• shotmr0.asm - Display TMR0 on a LCD atter counting pulses on RA4 for one second

Also:

• Interrupts@
• Debounce@

See also:

• http://avtanski.net/projects/astro_clock Multifunction PIC clock - timezones, moon phases, astronomy+
• Michael refers to http://www.sophtware.com/2008/08/pic_timer_calculator_1.html Frustrated over having to compute offsets for Timer0 all the time, I finally broke down and wrote my own Windows application to do the work for me. It works for 8-, 16-, and 32- bit mode timers that function like Timer0. That is, they only have a 'prescalar' and an 'offset'.  This calculator not only displays the period for a given prescalar and offset, but it will also compute those values for you given a desired period (delay). The application is flexible, and if I get some feedback, I'll update it later to include all the other timers on the various PIC chips.  Oh, it's free too.
• Richard H McCorkle of Solid State Services refers to /techref/member/RHM-SSS-SC4/TIC232.htm Simple Interval Timer with RS232 output.
• http://www.time.com interesting
• http://stud.uni-sb.de/~maro0019/delay05.asm
• http://www.people.cornell.edu/pages/shb7/lop.html
• http://www.skyinet.net/~ecb/#isochronous delay
• Microchip app note "Technique to Calculate Day of Week"
• http://www.rt66.com/~shera/ppsdiv.zip The PIC source code for a single chip frequency divider that takes a 10 MHz input and produces 9 square wave outputs - one for each frequency decade from 100 kHz to 0.001 Hz (1000 s period), courtesy of Tom Van Baak, tvb@veritas.com:
• http://www.rt66.com/~shera/index_fs.htm Brooks Shera's GPS-Controlled Frequency Standard
• http://www.elecdesign.com/magazine/1998/sept0198/ifd/3IFD.pdf "Microcontroller controls its own clock speed" One chip and 2 xtals.

Archive

• PICList post "Timer Tribulations" Using house mains w/o pugging in
• PICList post "Timer Tribulations"
• PICList post "simple one-second timer"

Questions:

• KILLspampaultbarton.1944spam at STOPspamgmail.com asks:

  I would like to see an RTC for the Tandy coco-1-2-3. I envision a PIC (like 18f2321/4321 or thereabouts) one that has the parallel port I/O. The port would accept simple commands like: set time, read time. I think this can be done and made to be connected to any 8-bit computer. Thanks.

  +
• KILLspambasmangeorgespam at STOPspamgmail.com asks:

  I have a problem with using CCP pins for measuring time difference between two pulls signals where by timer1 will bee running free and CCP1capture is red throw CCPR1H-CCPR1L and CCP2 throw CCPR2H-CCPR2L complementing CCPR1H-CCPR1L and adding it to CCPR2H-CCPR2L after converting to ASCII and display on LCD the time measurement constantly flatcars with what looks like a random number and back to accurate measurement
  Welcome any suggestions
  Thanks Boz

• Hi all,
  I am working on a project in which I need to count incoming pulses from an optical encoder (DC Motor speed feedback). I want to count incoming pulses for 10 msec but couldn't figure out how to use Timers/ Interrupts or Delay. Conceptually it looks simple but.. I am writing code on CCS C. Please guide.
  
  Thanks,
  Chandresh+
• KILLspambob_the_batspam at STOPspamhotmail.com asks:

  There are commercial speedometer calibrators available for electronic speedometers, and they are adjustable to compensate for different tire diameters, pressure, gear ratios, etc. Does anyone know how this could be accomplished with a PIC? The output from the speedometer pickup is a 5 volt pulse with a maximum frequency of 21khz. The device wires in between the speedo pickup and the speedometer.
  
  Thanks in advance, Bob

• KILLspamsreerangapspam at STOPspamyahoo.com asks:

  i am using Pic 18c452. i am using Hitech C compiler and i am unable to get how the prescaler is used and how the Tmr0l and Tmr0H should be assigned . plz do explain to me how to get acquianted with the timer. Thanking you sree

• Omar Fathalllah asks:

  I'm just starting to experiment with the PIC16F877 using the HITECH C compiler. I am running the PIC at 10 Mhz and want a 50 MHz PWM period with a 7.5% duty cycle. However this means that I need the PR2 to be 3124 which is too large (max is 255 right?). Is there a way around this? am I doing something wrong? or do I have to use a 4MHz clock instead? or maybe create my own pulse using TIMER0 which would allow a prescalar of 256? Thanks in advance!

Archive:

• List post "16 bit Mod 7 Math" useful for calculating the Zeller Congruence +
• PICList post "BCD time-of-day addition" +

See:

• /techref/piclist/cheapic/eggtim4m.asm
• /techref/microchip/math/index.htm PIC Microcontoller Math Methods+
• /techref/microchip/math/basic.htm PIC Microcontoller Basic Math Methods+
• /techref/microchip/math/incdec/index.htm  PIC Microcontoller Basic Math Inc/Dec Methods
• /techref/microchip/12ceeprom.htm PIC Microcontoller Memory Method - Internal EEPROM access on 12CExxx devices
• /techref/microchip/io/audio.htm PIC Microcontoller Audio Input / Output +
• /techref/microchip/math/filter.htm PIC Microcontoller DSP Math Methods+
• /techref/microchip/edgedetect.htm Detecting riseing and falling edge events+
• /techref/microchip/sersamp.htm PIC Microcontoller IO Method High speed serial IO pin sampleing+
• /techref/microchip/ios.htm PIC Microcontoller Input / Output Methods+
• /techref/microchip/index.htm Technical Reference - MicroChip Technologies - PIC Embedded Controller+