Post by thread:two little ones and a BIG one, what ?... ALSO

Thus spake Kerzer Computers (spam_OUTkerzerTakeThisOuTSAMARA.CO.ZW): > Using a PIC16C84, How do detect two pulses in a one second time frame, > check that they are both longer than 100ms and wether or not they occurred > in half a second or one second. And to really complicate things, run two > independant timers, one between 1/2 and 4 hours, and the other between 3 and > 10 minutes ? Each one resetable by the pulse train in the begining of this > query ?Are you able to give me some advice or some code please ? Please > mail me direct so the list does not get cluttered up. Thankyou This is a reasonable question to answer on the list; that's the point of the list, is that more more people can learn by listening. I would approach this problem by performing everything in a big loop, calling subroutines as appropriate, but doing things in a very fixed order. The loop should be synchronized to the timer such that at the beginning of the loop you wait for timer overflow, then reset the timer to a value to overflow again in a certain time. This is the minimum resolution of the system - in your case if 100ms is the smallest time you need to measure, set the loop time to something less than this, e.g. 5ms. Make the loop work like this: Wait for overflow; Reset timer; Update software timer 1; Update software timer 2; Check input status; if changed start a software timer to measure pulse length; etc... Everything is timed from the basic loop duration - e.g. the 2 independent timers are done as software timers, using however many bytes of counter as needed, in units of 5ms or whatever the main loop is. Make sure you can do everything in the loop in 5ms - if not, do some things only on alternate loops or less often - use a state variable to divvy up the work, i.e. have a byte that is incremented each loop time; if bit 0 of the state variable is set, do things that you need done every second loop time, if bits 0-2 are all set do things you need done every 8th loop (40ms) etc. This kind of structure will guarantee determinism (but be sure you do not exceed the loop time - you can check for this by checking the hardware timer value at the beginning of the loop - if it has already overflowed you took too long - also toggle an output and watch it with a CRO - look for long pulses) and is easy to add new tasks, without the overhead of true multi-tasking. It is likely you will not need interrupts (which add non-determinism) or at least use interrupts only for very minimal stuff. -- Clyde Smith-Stubbs | HI-TECH Software, | Voice: +61 7 3354 2411 .....clydeKILLspam@spam@htsoft.com | P.O. Box 103, Alderley, | Fax: +61 7 3354 2422 http://www.htsoft.com | QLD, 4051, AUSTRALIA. | --------------------------------------------------------------------------- Download a FREE beta version of our new ANSI C compiler for the PIC microcontroller! Point your WWW browser at http://www.htsoft.com/

I am really new at this, can you explain in more detail please ? At 21:39 6/01/97 +1000, you wrote: {Quote hidden}>Thus spake Kerzer Computers (kerzerKILLspamSAMARA.CO.ZW): > >> Using a PIC16C84, How do detect two pulses in a one second time frame, >> check that they are both longer than 100ms and wether or not they occurred >> in half a second or one second. And to really complicate things, run two >> independant timers, one between 1/2 and 4 hours, and the other between 3 and >> 10 minutes ? Each one resetable by the pulse train in the begining of this >> query ?Are you able to give me some advice or some code please ? Please >> mail me direct so the list does not get cluttered up. Thankyou > >This is a reasonable question to answer on the list; that's the point of the >list, is that more more people can learn by listening. > >I would approach this problem by performing everything in a big loop, >calling subroutines as appropriate, but doing things in a very fixed >order. The loop should be synchronized to the timer such that at >the beginning of the loop you wait for timer overflow, then reset the >timer to a value to overflow again in a certain time. This is the minimum >resolution of the system - in your case if 100ms is the smallest time you >need to measure, set the loop time to something less than this, e.g. 5ms. > >Make the loop work like this: > > Wait for overflow; > Reset timer; > Update software timer 1; > Update software timer 2; > Check input status; if changed start a software timer > to measure pulse length; > etc... > >Everything is timed from the basic loop duration - e.g. the 2 independent >timers are done as software timers, using however many bytes of counter as >needed, in units of 5ms or whatever the main loop is. Make sure you can >do everything in the loop in 5ms - if not, do some things only on alternate >loops or less often - use a state variable to divvy up the work, i.e. have >a byte that is incremented each loop time; if bit 0 of the state variable >is set, do things that you need done every second loop time, if bits 0-2 >are all set do things you need done every 8th loop (40ms) etc. > >This kind of structure will guarantee determinism (but be sure you do not >exceed the loop time - you can check for this by checking the hardware timer >value at the beginning of the loop - if it has already overflowed you took >too long - also toggle an output and watch it with a CRO - look for long >pulses) and is easy to add new tasks, without the overhead of true >multi-tasking. It is likely you will not need interrupts (which add >non-determinism) or at least use interrupts only for very minimal >stuff. > > > >-- >Clyde Smith-Stubbs | HI-TECH Software, | Voice: +61 7 3354 2411 >.....clydeKILLspam.....htsoft.com | P.O. Box 103, Alderley, | Fax: +61 7 3354 2422 >http://www.htsoft.com | QLD, 4051, AUSTRALIA. | >--------------------------------------------------------------------------- >Download a FREE beta version of our new ANSI C compiler for the PIC >microcontroller! Point your WWW browser at http://www.htsoft.com/ > >

Maybe I can help answer this one. I hope this isn't too long for the list. The project I worked on had eight timers and about seven inputs to process in "real time". The processor is the 16C57 so I'm sure you'll have greater flexibility with the '84. The main event loop is executed as fast as it takes to get throught the instructions. The time to get through the event loop is less than the loop timer. In this case the loop timer was set to about 7mS. 'check timers' and some hardware configuring is done every cycle of the loop while only one state is active. All of this only works if you can afford a lower resolution of your time measurment. In this example the best resolution of a button press is 7mS. If your timing requirements are minutes or hours then maybe +/- 7mS is OK. You can also change the loop timer around to meet your needs. It looks kind of like this: ________________________________________________________________ Start of program ;---- initialize all hardware ---- blah blah blah ;======================================= ;= TOP OF HEADSET EVENT LOOP = ;======================================= Top_of_event_loop ;---- reset watchdog timer ---- clrwdt ;---- do some hardware checking ---- blah blah blah ;---- check all timers ---- PAGE_2 goto Check_Timers timersReturn ;---- This is the state processing section ;---- A variable 'state' is compared to a constant 'STATEx' ;---- if they match then that 'State' is processed. ;---- Changeing states is done inside the current state. ;---- Check Program State ---- movlw STATE1 subwf state, W JNZ stState2 PAGE_2 goto State_1 stState2 movlw STATE2 subwf state, W JNZ stState3 PAGE_2 goto stState2 . . . . ;---- add as many states as you want as long as the processing time for any one ;---- state doesn't take longer than the loop timer. . . . stateReturn ;---- do some hardware checking ---- blah blah blah ;---- check battery ---- goto Check_Battery_Low Check_Battery_Low_Return ;---- check Shut Down ---- goto Check_ShutDn Check_ShutDn_return goto Top_of_event_loop ;======================================= ;= END OF HEADSET EVENT LOOP = ;======================================= _______________________________________________________________ Here are the inputs and timers routine. There is one example of the battery input signal and associated debounce and shutdown timer but you can add a lot more inputs and timers in here if you need them. ________________________________________________________________ ;************************************************************* ; GOTO: Check_Timers ;************************************************************* Check_Timers BANK_0 movf RTCC, W ; get timer value subwf RTCC_last, Same ; if RTCC_last > RTCC, C=1, Z=0 (overflo w) ; if RTCC_last = RTCC, C=1, Z=1 ; if RTCC_last < RTCC, C=0, Z=0 movwf RTCC_last ; save for next time JZ check_out ; if RTCC_last = RTCC, then return... JNC check_out ; if RTCC_last < RTCC, then return... ;================================== ; PROCESS 8ms TIMER EVENT!!! ;================================== ;-------------------------------- ; DEBOUNCE VARIOUS SIGNALS ;-------------------------------- ;==== debounce Battery Low signal ==== ;---- set C to port value ---- btfsc PORT_LOWBATT, _LOWBATT STC btfss PORT_LOWBATT, _LOWBATT CLC ;---- shift into 'battlow_history' byte and mask unused bits ---- rlf battlow_history, W andlw 7fh ; 7 bits = 7 * 8ms debounce = 56ms movwf battlow_history ;---- if all bits are same, then set 'battery_low' flag ---- btfsc STATUS, Z ; skip if battlow not 0 bcf flag2, battery_low ; *** battery_low = 0 *** movlw 7fh subwf battlow_history, W btfsc STATUS, Z ; Z set if all 1's bsf flag2, battery_low ; *** battery_low = 1 *** ;------------------------------ ; PROCESS VARIOUS TIMERS ;------------------------------ ;==== process 'Battery_low_timer' ==== ;---- is timer > 0? ---- movf Battery_low_timer_l, Same JNZ battlow_active ; timer active... movf Battery_low_timer_h, Same JZ battlow_done ; timer not active... battlow_active ;---- decrement 16-bit timer ---- DJNZ Battery_low_timer_l, battlow_done movf Battery_low_timer_h, Same JZ battlow_expired ; if timer expired... decf Battery_low_timer_h, Same ; else decrement decf Battery_low_timer_l, Same ; (decr to prevent timer=0) goto battlow_done ; and we're done... battlow_expired ;---- Battery low timer expired! Beep the speaker ---- PAGE_3 ; routine located in ROM page 3 movlw BEEP_BATTLOW call Beep ; Beep(batterylow) PAGE_2 ; back to ROM page 2 BANK_1 ; and back to RAM bank 1 battlow_done check_out BANK_0 ; restore RAM bank to 0 PAGE_0 goto timersReturn At 01:10 PM 1/6/97 +0200, you wrote: snip {Quote hidden}> >Using a PIC16C84, How do detect two pulses in a one second time frame, >check that they are both longer than 100ms and wether or not they occurred >in half a second or one second. And to really complicate things, run two >independant timers, one between 1/2 and 4 hours, and the other between 3 and >10 minutes ? Each one resetable by the pulse train in the begining of this >query ?Are you able to give me some advice or some code please ? Please >mail me direct so the list does not get cluttered up. Thankyou > >Gordon > > ----------------------------------------------------------------------------- EraseMEbryanspam_OUTTakeThisOuTwllink.com Wireless Link Corporation -----------------------------------------------------------------------------