Technical RPM counter

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Technical RPM counter

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nmrmak

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probably because it's the one that gives 1 pulse per 2 rpm or something.
Seen the link, my sei is not a sporting, so i don't have access to that connector... any other ideas?

I'd like to cut the coil wire and tap into it with my rev counter, then pass the wire to the steering wheel somehow, just like the horn wires. Any ideas? or would it be easier to place the rpm counter somewhere else?
 
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nmrmak

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Here is the code for Atmel 89S8253, as promised.
Feel free to modify it, hack it, improve it, port it to some other MCU, show it to your mother or print it on a piece of toilet paper and use it in some other way. :) It's yours as much as it's mine

That was the licence. Now i'd like to say i don't claim it works (even though it does for me), i don't take any responsibility if you fry your car / MCU / ECU / dog by using this code, and so on.

Now that we're through with the legal stuff, it actually works. I tested it today on a development board, and i'll be making a schematics for my own PCB that will be installed somewhere in the car in the next few weeks. I will not post the schematics until i am sure that it works. Maybe i'll post some new code then, that will match the new schematics, remove the debugging lines and so on.

Happy hacking your car :)

Code:
;************************************************
;* Project:    Fiat Seicento RPM counter    *
;* Author:    Nebojsa Mrmak            *
;* Date:    04 Feb 2008            *
;*                        *
;* Note:    Check out www.fiatforum.com    *
;*        for more information        *
;************************************************



    ORG    0000h
    MOV    SP,#030h        ;stack pointer vector
    JMP    INIT    

    ORG    013h            ;interrupt that occurs when a pulse is detected
    JMP    PULSE


    ORG    01Bh            ;Timer 1 interrupt vector
    JMP    INT_T1            ;Jump to the timer1 interrupt routine
    
INIT:                    ;initialize our stuff
    ORG    100h            ;program start vector
    SETB    PX1
    MOV    TMOD,#00010001b        ;establish T1 as a 16 bit timer - at 12MHz ~ 0.1s
    MOV    IE,#10001100b        ;enable ints, enable T1, INT0 int. 
    MOV    TH1,#11111101b        ;reset the timer
    MOV    TL1,#11110000b        ; -||-
    ;init some values here:
    MOV    P1,#1
    MOV    R0,#0
    MOV    R1,#0
    MOV    R2,#0
    MOV    R3,#0
    MOV    R4,#0
    MOV    R5,#0
    MOV    R6,#0
    MOV    R7,#0
    MOV    0018h,#0
    MOV    0019h,#0
    MOV    001Ah,#0
    MOV    001Bh,#0
    MOV    TCON,#01010000b     ;start the timer
MAIN:
    ;The following four blocks are used to display the numbers on four 7-seg displays.
    MOV    A,#0
    ACALL    MASK
    MOV    P1,#0
    MOV    P0,A
    MOV    P1,#1
    
    MOV    A,0018h
    ACALL    MASK
    MOV    P1,#0
    MOV    P0,A
    MOV    P1,#2

    MOV    A,0019h
    ACALL    MASK
    MOV    P1,#0
    MOV    P0,A
    MOV    P1,#4

    MOV    A,001Ah
    ACALL    MASK
    MOV    P1,#0
    MOV    P0,A
    MOV    P1,#8
    ;and repeat.
    JMP     MAIN

INT_T1: 
    ;timer overflow interrupt!
    PUSH    ACC
    PUSH    PSW
    MOV    TH1,#11111101b        ;reset the timer
    MOV    TL1,#11110000b        ; -||-
    CPL    P3.0    ;just flash a debug LED, safe to remove this line
    MOV    A,R0
    ADD    A,#10
    JNC    NO_OVERFLOW
    INC    R1
NO_OVERFLOW:
    ;if the low byte of the timer is still less than 255
    MOV    R0,A
    POP    PSW    
    POP    ACC
    RETI ;end timer overflow interrupt here

PULSE:
    ;ecu LT pulse interrupt start!
    MOV    80A7h,#10101011b ;reset the watchdog timer. 

    ;delay a little, debouncing while i was testing it with a button. 
    ;Possibly safe to remove when in a car, ecu shouldn't have bounce.
    MOV    R7,#10 
LOOP:    MOV    R6,#10
    DJNZ    R6,$
    DJNZ    R7,LOOP
    ;end delay
    JB    P3.3,NEXT    ;if button is still pressed, do the interrupt
    RETI            ;else return from interrupt
NEXT:    
    MOV    TCON,#00000000b        ;stop the timer
    PUSH    ACC
    PUSH    PSW
    MOV    P2,R0    ;debug, outputs R0 value to port 2, safe to remove this line

    MOV    A,R0    ;push R0 and R1 onto the stack
    PUSH    ACC    ;R0 and R1 hold the number of times the timer overflowed x10, and since it overflows once each
    MOV    A,R1    ;1ms, then it's the number of ms passed between 2 revs
    PUSH    ACC

    ;the following block practically divides the timer by 66 
    ;(max. value the timer can achieve is 666, so you get 1/10 of that value, and the max is 0.001s)
    MOV    A,TL1    
    MOV    R2,A    ;move TL1 to r2 (TL1 - timer 1 lower byte)
    MOV    A,TH1
    MOV    R3,A    ;move TH1 to r3    (TH1 - timer 1 higher byte)
    MOV    R1,#66    ;move 66 to R1 and 0 to R0 so we can divide
    MOV    R0,#0
    LCALL    div16_16    ;call the division routine (borrowed from someone else)
    MOV    A,R2    ;put the lower byte of the result into 0018h
    MOV    0018h,A
    POP     ACC    ;pop R1 and R0 from the stack
    MOV    R1,A
    POP    ACC
    MOV    R0,A

    MOV    A,R0    ;add the calculated number of ms on the timer to the number of overflows
    ADD    A,0018h
    JNC    NO_OVERFLOW1
    INC    R1
NO_OVERFLOW1:

    
TEST0:    ;a small test to see if we're going to divide by 0 (we don't want that)
    CJNE     R1,#0,TEST_END     ;if either register is non-zero, carry on
    CJNE    R0,#0,TEST_END
    POP    PSW         ;if both are zero, pop the values from the stack and return from interrupt 
    POP    ACC        ;better to give up here than divide by 0, we'll get the rpm on the next 2 pulses
    RETI
TEST_END:
    
    MOV    A,R0
    MOV    R2,A
    MOV    A,R1
    MOV    R3,A
    MOV    R1,#11101010b
    MOV    R0,#01100000b
    LCALL    div16_16     ;get the rpm using the formula: 60000/10* ms passed

    MOV    A,R3
    MOV    R1,A
    MOV    A,R2
    MOV    R0,A

    ;the following few blocks divide by 10, and get the individual digits that we're to output on our 7-segment displays
    ;for example, 1234 rpm:
    ;1234 div 10 = 123, mod = 4, least significant digit is 4
    ;123 div 10 = 12, mod = 3, second digit is 3
    ;12 div 10 = 1, mod = 2, third is 2, fourth is 1
    ;save each digit to it's designated ram address, which will be read and displayed in the main loop.
    ;note that the least significant digit is always zero, to make the display more readable (less fluctuations, easier code)
    ;and why the hell would you care if you're at 3501 or 3500 rmm anyway? :)
    MOV    R3,#0
    MOV    R2,#10
    LCALL    div16_16
    
    MOV    A,R0
    MOV    0018h,A


    MOV    A,R3
    MOV    R1,A
    MOV    A,R2
    MOV    R0,A

    MOV    R3,#0
    MOV    R2,#10
    LCALL    div16_16

    MOV    A,R0
    MOV    0019h,A

    MOV    A,R3
    MOV    R1,A
    MOV    A,R2
    MOV    R0,A

    MOV    R3,#0
    MOV    R2,#10
    LCALL    div16_16


    MOV    A,R0
    MOV    001Ah,A

    MOV    A,R3
    MOV    R1,A
    MOV    A,R2
    MOV    R0,A

    MOV    R3,#0
    MOV    R2,#10
    LCALL    div16_16


    MOV    A,R0
    MOV    001Bh,A
    
    CPL    P2.1 ;debug, safe to remove this line


    MOV    TH1,#11111101b        ;reset the timer
    MOV    TL1,#11110000b        ; -||-
    MOV    R0,#0            ;reset the overflow counter
    MOV    R1,#0
    POP    PSW
    POP    ACC
    MOV    TCON,#01010000b        ;re-start the timer
    RETI    ;return from interrupt

MASK:                           ; Subroutine that translates digits to 7seg
        INC     A
        MOVC    A,@A+PC
        RET
        DB    0C0H        ; Mask for 0
        DB      0F9H            ; Mask for 1
        DB      0A4H            ; Mask for 2
        DB      0B0H            ; Mask for 3
        DB      099H            ; Mask for 4
        DB      092H            ; Mask for 5
        DB      082H            ; Mask for 6
        DB      0F8H            ; Mask for 7
        DB      080H            ; Mask for 8
        DB      090H            ; Mask for 9

; **** the following routine is NOT mine, i borrowed it from www.8052.com since i couldn't have been bothered to write my own.
; **** it's very well documented, so you should have no problems with it if you need to know how it works anyway
; **** it divides R1R0 by R3R2 in 16 bit and stores the result in R3/R2 and the rest in R1/R0

div16_16:
  CLR C       ;Clear carry initially
  MOV R4,#00h ;Clear R4 working variable initially
  MOV R5,#00h ;CLear R5 working variable initially
  MOV B,#00h  ;Clear B since B will count the number of left-shifted bits
div1:
  INC B      ;Increment counter for each left shift
  MOV A,R2   ;Move the current divisor low byte into the accumulator
  RLC A      ;Shift low-byte left, rotate through carry to apply highest bit to high-byte
  MOV R2,A   ;Save the updated divisor low-byte
  MOV A,R3   ;Move the current divisor high byte into the accumulator
  RLC A      ;Shift high-byte left high, rotating in carry from low-byte
  MOV R3,A   ;Save the updated divisor high-byte
  JNC div1   ;Repeat until carry flag is set from high-byte
div2:        ;Shift right the divisor
  MOV A,R3   ;Move high-byte of divisor into accumulator
  RRC A      ;Rotate high-byte of divisor right and into carry
  MOV R3,A   ;Save updated value of high-byte of divisor
  MOV A,R2   ;Move low-byte of divisor into accumulator
  RRC A      ;Rotate low-byte of divisor right, with carry from high-byte
  MOV R2,A   ;Save updated value of low-byte of divisor
  CLR C      ;Clear carry, we don't need it anymore
  MOV 07h,R1 ;Make a safe copy of the dividend high-byte
  MOV 06h,R0 ;Make a safe copy of the dividend low-byte
  MOV A,R0   ;Move low-byte of dividend into accumulator
  SUBB A,R2  ;Dividend - shifted divisor = result bit (no factor, only 0 or 1)
  MOV R0,A   ;Save updated dividend 
  MOV A,R1   ;Move high-byte of dividend into accumulator
  SUBB A,R3  ;Subtract high-byte of divisor (all together 16-bit substraction)
  MOV R1,A   ;Save updated high-byte back in high-byte of divisor
  JNC div3   ;If carry flag is NOT set, result is 1
  MOV R1,07h ;Otherwise result is 0, save copy of divisor to undo subtraction
  MOV R0,06h
div3:
  CPL C      ;Invert carry, so it can be directly copied into result
  MOV A,R4 
  RLC A      ;Shift carry flag into temporary result
  MOV R4,A   
  MOV A,R5
  RLC A
  MOV R5,A        
  DJNZ B,div2 ;Now count backwards and repeat until "B" is zero
  MOV R3,05h  ;Move result to R3/R2
  MOV R2,04h  ;Move result to R3/R2
  RET

END

Oh, and by the way... seriously, how do i get the wires from the engine compartment to the dash? is there a hole in the firewall, and where is it? I'm sure there is one, i just couldn't find it today. Pics of it would be great!

Thank you all for your support :) :slayer:
 
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No easy hole.


If its a modern sei, then there is a grommet above the accelerator pedal, but thats a long length of wire.


I did this:

https://www.fiatforum.com/cinq-sei-technical/109258-megasquirt-construction-project.html

post 24. Just drilled a very messy hole :eek:


Those wires for the rev counter may be behind the dash even though you don't have one. Quite often it's easier to fit a standard loom, and just hide and not use parts.



Kristian
 
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nmrmak

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The problem is, that the code i wrote and the hardware i am building is made for picking up the LT signal at the coil. I'm not sure it would work with the stock rev wires. Are you sure that non-sporting seis have those connectors too? there is no hole on the dask, so i'd have to pull the dash off to find it, which isn't an easy task at all.

Also, my system will probably do some other stuff, like run a foglights relay and possibly some central locking stuff and temp. sensing that intend to play with so i can learn some new stuff.

Actually, i think i'll have to remove the dash anyway. Is there a way to remove just the two central vent blower thingys?
 
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You can remove the centre switch panel and have a poke around. There's no guarantee that the wires will be there.
I used a 20mm hole saw with an extension to make a new hole and fitted a grommet.
 
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nmrmak

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Wait, how do you remove the centre panel? I didn't see any screws when i looked at it.
 
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nmrmak

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Thanks, i'll try sneaking the wires through there somehow. I don't like the idea of having to put my electronics into the speaker hole.

Oh, by the way, i think i'll put the display upside down horizontally under the windshield, so i can see the reflection of it in the glass, hopefully it'll look nice :D
I will need some pretty strong LED displays for that though...
 
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nmrmak

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It's the least of a problem to mirror the display since it's a 7segment one and i'm writing the software for it, it's just a matter of changing the values in the "MASK" routine in the code ;)

Cheers :)
 
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nmrmak

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It's a no-go on reflecting the displays on the windscreen because it has considerable thickness, so you actually see TWO reflections, which looks like crap. Any ideas where a rpm display (four 7-segment displays) could be mounted so it's practical to see during a ride?
 
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nmrmak

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The schematics, as promised:

the second part (the display pcb) soon to come, along with the pcb images / gifs. That might take a few days, possibly weeks, because i have some important exams @ uni.
 

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nmrmak

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Perhaps it would be illegal, but it would certainly be unreadabre, because the windscreen has a certain thickness (about 5-6 mm maybe?) and you can clearly see two reflections because of that, so that's not an option. I'm having the pcb made next week probably, and then i'm gonna install it. the display would be a separate module so i can place it wherever i want. I still haven't figured out a good place for it though...
 
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