|
Re: Real time clock + external interrupt in one PIC possible?
Hello Henrik,
thank you in advance for your input. I get one pulse per driveshaft revolution that drives the car ca. 0.6m .
I don´t expect any road mission like this to exceed 8 minutes so 600 seconds as upper limit should do.
regards and greetings to sweden (had some nice days in Malmö 4 years ago)
Mugelpower
|
Re: Real time clock + external interrupt in one PIC possible?
Thanks, give me some time and I'll get back to you with a starting point.
Is it likely that the distance traveled will be more than 39km?
/Henrik.
|
Re: Real time clock + external interrupt in one PIC possible?
Hello Henrik,
no, the maximum distance we have experienced were less than 3 km, so 10km will be sufficcient. Problem would be that the road mission is on public roads that are temporary closed for about 2 hours and it´s difficult here in Germany, especially in Northrhein Westfalia to find roads that long which could be blocked from public access so the Oldtimers could drive their road mission. Northrhein Westfalia is the most dense populated federal state in Germany and has 524 People per square km. For comparison Sweden has 24 People per square km.
regards
Mugelpower
|
Re: Real time clock + external interrupt in one PIC possible?
Laying in bed thinking about this project, I'm guessing you want to calculate an average speed from the time you hit the go pedal. I pondered how to do that with minimal code. Essentially I came up with:
Durchschnittlich var WORD ;Speed
Geschwindigkeit var WORD ;Average
Teiler VAR WORD ;Divisor
Gesamt VAR LONG ;Total
DO
Durchschnittlich = TMR3 ;Using T3CKI with TMR1
Gesamt = Gesamt + Durchschnittlich
Teiler = Teiler + 1
Geschwindigkeit = Gesamt / Teiler
LOOP
Of course, the DO/LOOP would be paced per TMR1 Interrupt
|
Re: Real time clock + external interrupt in one PIC possible?
Hi,
I've written some code targeting the 18F1320, I thought I had a couple of those in stock and I just set out to build up a test circuit to verify the code but it was the 18F1330 I had and as it turns out it's a completely different beast (lacking a TMR2 which the code relies on for example).
I guess I could change the code to suit a device that I do have but then that might not be what you intend to run it on anyway and we'd still need some back and forth so I'll just post the code as is and ask you to kindly remember that it is untested. Hopefully though it serves its purpose and show you the overall idea of one way that this can be done without external RTC chips or interrupts.
There is a bit of code but I tried to make it as complete as I could for a first pass, I'm sure there are things I didn't think of though.
Feel free to pick it apart, ask questions why this or that.
Code:'**************************************************************** '* Name : Speedometer.pbp * '* Author : Henrik Olsson * '* Notice : Copyright (c) 2017 [select VIEW...EDITOR OPTIONS] * '* : All Rights Reserved * '* Date : 2017-09-13 * '* Version : 1.0 * '* Notes : Uses TMR1 configured as a counter to measure * '* distance traveled and TMR2 as a 2ms timebase to * '* measure real time. * '* An active low start/stop button is used to start * '* and stop the measurement. * '* * '* : Target is 18F1320 but running on internal 8MHz * '* oscillator but should work on any device having * '* a TMR1 and TMR2 with or without minor changes. * '* : * '**************************************************************** '-------------------- Device configuration ---------------------- #CONFIG CONFIG OSC = INTIO2 ; Internal RC oscillator, port function on RA6 and port function on RA7 CONFIG FSCM = ON ; Fail-Safe Clock Monitor enabled CONFIG IESO = ON ; Internal External Switchover mode enabled CONFIG PWRT = OFF ; PWRT disabled CONFIG BOR = ON ; Brown-out Reset enabled CONFIG BORV = 27 ; VBOR set to 2.7V CONFIG WDT = ON ; WDT enabled CONFIG WDTPS = 512 ; 1:512 CONFIG MCLRE = ON ; MCLR pin enabled, RA5 input pin disabled CONFIG STVR = ON ; Stack full/underflow will cause Reset CONFIG LVP = OFF ; Low-Voltage ICSP disabled CONFIG DEBUG = OFF ; Background debugger disabled, RB6 and RB7 configured as general purpose I/O pins CONFIG CP0 = OFF ; Block 0 (00200-000FFFh) not code-protected CONFIG CP1 = OFF ; Block 1 (001000-001FFFh) not code-protected CONFIG CPB = OFF ; Boot Block (000000-0001FFh) not code-protected CONFIG CPD = OFF ; Data EEPROM not code-protected CONFIG WRT0 = OFF ; Block 0 (00200-000FFFh) not write-protected CONFIG WRT1 = OFF ; Block 1 (001000-001FFFh) not write-protected CONFIG WRTC = OFF ; Configuration registers (300000-3000FFh) not write-protected CONFIG WRTB = OFF ; Boot Block (000000-0001FFh) not write-protected CONFIG WRTD = OFF ; Data EEPROM not write-protected CONFIG EBTR0 = OFF ; Block 0 (00200-000FFFh) not protected from table reads executed in other blocks CONFIG EBTR1 = OFF ; Block 1 (001000-001FFFh) not protected from table reads executed in other blocks CONFIG EBTRB = OFF ; Boot Block (000000-0001FFh) not protected from table reads executed in other blocks #ENDCONFIG '---------- Variables ------------ Seconds VAR WORD ' elapsed time, seconds ms VAR WORD ' elapsed time, milliseconds State VAR BYTE ' State machine variable, keeps track of what we're doing Distance VAR WORD ' Distance traveled in metres, calculated based on pulsecount AverageSpeed VAR WORD ' Final result of measurement, in units of 0.1km/h (123=12.3km/h) Temp var WORD ' Used during calculation DebounceCount VAR BYTE ' Used to debounce the start/stop button TimeOverflow VAR BIT ' Gets set if the seconds variable grows too big. '---------- Constants ------------- Idle CON 0 Starting CON 1 Counting CON 2 Stopping CON 3 Done CON 4 '------------ Aliases -------------- StartStopButton VAR PortB.0 ' Low when pressed ReadyIndicator VAR LATB.2 ' High when idle/ready RunIndicator VAR LATB.3 ' High when counting/timing ErrorIndicator VAR LATB.4 ' High on count or time overflow TMR1ON VAR T1CON.0 ' Run/stop bit for TMR1 TMR2ON VAR T2CON.2 ' Run/stop bit for TMR2 TMR1IF VAR PIR1.0 ' TMR1 interrupt flag TMR2IF VAR PIR1.1 ' TMR2 interrupt flag '--------- Hardware setup ----------- ADCON1 = %11111111 ' All pins as digital LATB = %00000000 ' All pins low TRISB = %01000001 ' RB0=Button, RB1=TX, RB2=LED, RB3=LED, RB4=LED, RB6=Counter input OSCCON = %01110010 ' Internal oscillator, 8MHz T1CON = %00000010 ' External clock on RB6, timer OFF for now. T2CON = %00000010 ' 1:16 prescaler, TMR2 off for now PR2 = 249 ' T2 interrupt flag set every 250*16 tick RCSTA = $90 ' Enable serial port & continuous receive TXSTA = $20 ' Enable transmit, BRGH = 0 SPBRG = 12 ' 38400 Baud @ 8MHz, 0,16% SPBRGH = 0 BAUDCTL.3 = 1 ' Enable 16 bit baudrate generator PAUSE 500 Start: HSEROUT["Program start",13] For Temp = 0 to 9 ReadyIndicator = 1 Pause 250 ReadyIndicator = 0 Pause 250 NEXT ReadyIndicator = 1 Main: Select CASE State Case Idle If StartStopButton = 0 THEN ' If the button is pressed we Seconds = 0 ms = 0 TMR1H = 0 ' reset the pulse count TMR1L = 0 TMR2 = 0 ' reset the timebase TMR1IF = 0 ' clear the overflow flag TMR2IF = 0 ' clear the timebase tick flag TMR1ON = 1 ' enable the counter to count pulses from the driveshaft TMR2ON = 1 ' enable the 2ms timer tick ReadyIndicator = 0 ' update status LEDs RunIndicator = 1 ErrorIndicator = 0 TimeOverflow = 0 ' clear overflow flag State = Starting ' and move to the next state. ENDIF '--------------------------------------------------------------------------------------------------- CASE Starting IF TMR2IF THEN ' TMR2IF gets set every 2ms TMR2IF = 0 ' reset flag GOSUB UpdateTime ' update our time registers ' Wait for the button to be released before transitioning to the next state. If StartStopButton = 1 THEN ' Button released? DebounceCount = DebounceCount + 1 ELSE DebounceCount = 0 ' Button must be released 10 ticks in a row. ENDIF IF DebounceCount = 9 THEN ' Button has been released for 10 ticks DebounceCount = 0 State = Counting ' Transition to next state. ENDIF ENDIF '--------------------------------------------------------------------------------------------------- Case Counting IF TMR2IF THEN ' 2ms tick? TMR2IF = 0 ' clear flag and GOSUB UpdateTime ' update our time registers If StartStopButton = 0 THEN ' Button pressed? RunIndicator = 0 TMR1ON = 0 ' Disable pulse counter TMR2ON = 0 ' Disable timer State = Stopping ENDIF ENDIF IF TMR1IF THEN ' Counter overflow ErrorIndicator = 1 ENDIF ' Here we can do anything else that needs doing while the ' system is counting but it's very important that it does ' not take longer than 2ms or we will lose time. '--------------------------------------------------------------------------------------------------- CASE Stopping ' Wait for the button to released before transitioning to the next state, If StartStopButton = 1 THEN ' Is button released? DebounceCount = DebounceCount + 1 ELSE DebounceCount = 0 ENDIF IF DebounceCount = 10 THEN ' Button released for duration of debounde time? DebounceCount = 0 State = Done ' Transition to next state. ENDIF ' The timer is no longer running so we pause here for the same duration. PAUSE 2 '--------------------------------------------------------------------------------------------------- CASE Done ' This is where we perform the calculations and present the result. If TMR1IF THEN ' Interrupt flag is set if counter has rolled over HSEROUT["ERROR: Pulse counter overflow, can't compute...", 13] Goto Abort ENDIF IF TimeOverflow THEN ' Flag set if seconds variable has rolled over HSEROUT["ERROR: Seconds counter overflow, can't compute...", 13] Goto Abort ENDIF ' Each count from the driveshaft equals 0.6m of car movement. ' Lets say the pulse count is 12345 and the seconds count is 503. ' We've traveled 12345*0.6=7407 metres in 503 seconds, 7407/503*3.6=53.0km/h ' Using the ** operator allows us to effectively multiply by fractions of 65536 so: ' ' 12345 ** 39322 = 7407 ' 7407 * 36 = 266652 ' 266652 / 503 = 530 which we interpret as 53.0km/h ' ' 6045 pulses in 312 seconds, ' 6045*0.6/312*3.6=41.85km/h: ' 6045 ** 39322 = 3627 ' 3627 * 36 = 130572 ' 130572 / 312 = 418 which we interpret at 41.8km/h ' ' 53203 pulses in 1412 seconds, ' 53203*0.6/1412*3.6=81.39km/h: ' 53202 ** 39322 = 31922 ' 31922 * 36 = 1149192 ' 1149192 / 1412 = 813 which we interpret as 81.3km/h Distance.HIGHBYTE = TMR1H Distance.lowbyte = TMR1L Distance = Distance ** 39322 ' Multiply by 0.6, Distance is now in metres Temp = Distance * 36 AverageSpeed = DIV32 Seconds ' 215 for 21.5km/h HSEROUT[DEC (TMR1H * 256 + TMR1L), " pulses",13] HSEROUT[DEC Distance, "m", 13] HSEROUT[DEC Seconds, ".", DEC3 ms, "s",13] HSEROUT[DEC AverageSpeed/10,".", DEC AverageSpeed//10, "km/h",13] Abort: ReadyIndicator = 1 ErrorIndicator = 0 State = Idle END SELECT Goto Main '-------------------------------------- Subroutines ------------------------------------------------ UpdateTime: ' Our timebase is 500Hz. ms = ms + 2 If ms = 1000 then ms = 0 seconds = seconds + 1 ' We're using DIV32 to calculate the average speed. It does not allow the divisor ' to be larger than 32767 (which is 9 hours and some minutes so it should be fine) ' but since we're good programmers we're going to check for it anyway. If Seconds > 32767 THEN TimeOverflow = 1 ErrorIndicator = 1 ENDIF ENDIF RETURN
|
Re: Real time clock + external interrupt in one PIC possible?
Hello Henrik,
thanks a lot, I´ve never be able to program that way and so long, I´m more the "Hello World" guy.
Is it possible to put a "LCDOUT" in betwen or does it take more than 2ms ? I need a display as interface.
Do I need a serial LCD display?
regards
Mugelpower
|
Re: Real time clock + external interrupt in one PIC possible?
You can use a LCD and replace the HSEROUT statements with LCDOUT if you want. When the measurement is complete it doesn't matter how long it takes because then we're not timing anymore.
If you want the display to update DURING the measurment (like showing elapsed time) it'll be a bit more complicated - you never said anything about that I don't think :-)
It's certainly doable but we'll need to think about how to best do it. But highly I suggest getting a prototype up and running FIRST.
/Henrik.
|
Re: Real time clock + external interrupt in one PIC possible?
Hello Harry,
sorry about that . For me it was so obvious you have to drive the car with constant speed so you need to check the speedo the whole time. And I want to build a precise speedo that shows not only the actual speed but the average speed including stops, accelerations etc. Its impossible to drive a constant speed without a closed loop. Its not a straight road to drive but the roads have turns and maybe a stop. And we don´t know wheres the end of
the measured distance so we have to maintain the average speed until the end of the road mission is cleary marked.
So yes, we have to look constantly on the speedo , aybe more on the speedo than on the road.
Regards
Mugelpower
|
Re: Real time clock + external interrupt in one PIC possible?
Yes I´m beginning to build the prototype next weekend.
Greetings to all earthlings
Members who have read this thread : 1You do not have permission to view the list of names.
Posting Permissions
Bookmarks