16F877A system control to tachometer (FIS version) on the table

[mazoul72]

Hello,

my project :

FIS control like VAG (home display , VAG-COM like , Soft coding change on the fly ...)

problem : software---> program modification with already based Version 1.0
                                 frame to decode with K-LINE (control bytes sequence already have but have to improve) or BUSCAN (but very hard to decode)

              hardware : ---> 1) problem with outputs RESET/DOWN/UP steering wheel commands
                                     2) to conceive some more functions..

The system is on the "table" but need to modify 3 wires on Green connector (23 / 24 / 25 ) :


a PIC16F877A that is in serial with steering wheel command (RESET / UP / DOWN on B5,B6 et B7)
I am programing to put ground on outputs (RC3 ,RC4 ,RC5 ) but for valid UP/DW/RESET i need transistion from +12V to ground .

Also i need absolutely 12V like FIS send to input (normally) and PIC has only +5V to 3 wires .
How have +12V on RC3 ,RC4 and RC5 outputs command by my program ? (pull-up resistors ??)

Opto-isolator but how plug to RCx 3 wires ??

+12V is normaly on 23/24/25 input ("on the air" wires) --> not lie to external Ground(perhaps internal FIS tachometer...) .
If the soft PIC put +12V (output RCx) on +12V FIS , hardware failure.... so no +12V  force but only Ground with  external input command buttons . 

                                  

[TomJackson69]

Not really understand what you want. Do you want to convert +12V to +5V signal to input to the PIC (pin B5, B6 and B7)?

Be clearer for us to understand what you want.

Tom

[gan_canny]

The issue is that a PIC is 5v and the input output levels are 12v.
 If the circuit doesn't need isolated grounds.
 On the input side a resistor divider could split the voltage eg 5k 7k. The output needs a level shifter. Here a 74xx hex non-inverting  or inverting ( do the inversion in the MCU) open collector would likely work.
If the circuit  needs isolated grounds.
 If isolation is needed then the opto isolator would work.

[zokij]

not expensive but will reliable to use TLP504A on both side (portb and portc)

[mazoul72]

Hi,
thanks for aswers .
i put option_reg.7 for pull-up RB5 to RB7 (input steering wheel) and RB0 to RB2 (radio display on FIS tacho) .
I have for it an ASM prog but i've just seen that i didn't put TRISB %11100111 for input RB.
Is it for this mistake i have +6.7V(RB7,RB6) and 4.98V(RB5) : VERY Strange ...
My input PIC Voltage is stable at 4.98V .

Start:

ASM

loop
BTFSS PORTB.5 ; jump next instruction if B.5 = "1"
BCF PORTC.3 ; put C.3 à "0" (B5 input and C3 output)
BTFSC PORTB.5 ; jump next instruction if B.5 = "0"
BSF PORTC.3 ; put C.3 à "1"


BTFSS PORTB.6 ; jump next instruction if B.6 = "1"
BCF PORTC.4 ; put C.4 to "0" (B6 input and C4 ouput)
BTFSC PORTB.6 ; jump next instruction if B.6 = "0"
BSF PORTC.4 ; put C.4 to "1"

;Si aucunes commandes validées alors on continu dans le programme complet
BTFSC PORTB.7 ; jump next instruction if B.7 = 0 (validation)
GoTo loop

ENDASM

mainprog:
action for each command.....on Fis display
if portb.7 = "0" then goto validmenu....
if portb.6 = "0" then menu=menu+1;goto fisdisplay
if portb.5 = "0" then menu=menu-1;goto fisdisplay
goto Start
fisdisplay:
....
...  lineK access
...
validmenu:...
...
...
return
END

[mazoul72]

PORTB.6 is at 3.5V , not 5V , i don't understand why
PORTB.5 and PORTB.7 is at 5V , very strange ...


Regards
Mazoul72

[pickit2]

A schematic might help. How are you getting >> "i have +6.7V(RB7,RB6) and 4.98V(RB5) : VERY Strange ..."
that is not so strange if your feeding 12v into output ports.

if your just driving 12v from the pic, why not use a fet as logic driver.

[mazoul72]

It is strange because all should be at 6.7V with 12V driving .
Without 12V from tachometer, in fact i have 5V on RB7 ,RB5 and on RB6 : 3.5V  .ld
all should be at 5V .

[pickit2]

if you have any pin higher than the vcc, then you have a problem, your 12V is leaking into ciruit, thats why request for schematic.
having a pin between > 0 to 5V is what you would see if static, having 3.5V means that pin is pulsing.
High longer than the Low, a pin at 2.5V would be 50%.

16f877 has an operating voltage range (2.0V to 5.5V) 6.7 is a killer for pics.

[mazoul72]

Hello,

my second approach is the K-line protocol

dato = data  of tachometer
ena = enable  " " " " "
clk = clock     " " " " "

Code:

 
      suma=0
         dat=126
         ShiftOut dato, clk, 5,[dat]
           suma=suma ^ dat
           
         rem High dato
         
         dat=237
         ShiftOut dato, clk, 5,[dat]
          suma=suma ^ dat
          
         rem Low dato
         
         dat=15
         ShiftOut dato, clk, 5,[dat]
          suma=suma ^ dat
         
         rem High dato
       
           For cont=0 TO 15        (DATA caracters in PIC EPROM )
           tmp=msg[cont]
            rem dat=255 - tmp
             dat= ~ tmp 
             suma=suma ^ dat
         
            ShiftOut dato, clk, 5,[dat]
           rem Low dato
         
         Next cont
         
           
            dat=suma + 1
            ShiftOut dato, clk, 5,[dat]
           rem  Low dato
         
         
            High ena
            

The problem is the data logging .
i have a log file but i don't know what is the difference between each value .