gear check using 2 switches

[[email protected]]

I have used two DPDT press-release switches to find the gear shift in two wheelers. The idea is to scan the switches at each gear and relatively find the next. So I used a global declaration for integer. I am sure that this logic will work to identify the gear position. The problem is my program. Usually it doesn't work. It compiles without errors but all the LEDs glow simultaneously! Pls help me experts.



#include <16F877A.h>
#device adc=8

#FUSES NOWDT //No Watch Dog Timer
#FUSES HS //High speed Osc (> 4mhz for PCM/PCH) (>10mhz for PCD)
#FUSES NOPUT //No Power Up Timer
#FUSES NOPROTECT //Code not protected from reading
#FUSES NODEBUG //No Debug mode for ICD
#FUSES NOBROWNOUT //No brownout reset
#FUSES NOLVP //No low voltage prgming, B3(PIC16) or B5(PIC18) used for I/O
#FUSES NOCPD //No EE protection
#FUSES NOWRT //Program memory not write protected

#use delay(clock=20000000)


#define S1 PIN_B1 //1st switch
#define S2 PIN_B2 //2nd switch

#define NEUTRAL PIN_B3 // 5 LED pins for representing gear
#define FIRST PIN_B4
#define SECOND PIN_B5
#define THIRD PIN_B6
#define FOURTH PIN_B7

int flag=0;//global declaration
int gear();
int neutral_gear();
int first_gear();
int second_gear();
int third_gear();
int fourth_gear();


int neutral_gear() // can change only to first gear or remain same
{
if(!input(S1)&&!input(S2))
{
flag=0; // no change in switches, so no change in flag value
return flag;
}

else if(!input(S1)&&input(S2))
{
flag=1; //switch logic changes, so flag value changes to represent 1st gear
return flag;
}
}


int first_gear() //can up-shift to 2nd or downshift to neutral or remain same
{
if(!input(S1)&&input(S2))
{
flag=1; // no change in switches, so no change in flag value
return flag;
}

else if(!input(S1)&&!input(S2))
{
flag=2; //switch logic changes, so flag value changes to represent 2nd gear
return flag;
}

else if(input(S1)&&input(S2))
{
flag=0; //switch logic changes, so flag value changes to represent neutral gear
return flag;
}
}


int second_gear() //can up-shift to third or down-shift to 2nd or remain same
{
if(!input(S1)&&!input(S2))
{
flag=2; // no change in switches, so no change in flag value
return flag;
}

else if(!input(S1)&&input(S2))
{
flag=3; //switch logic changes, so flag value changes to represent 3rd gear
return flag;
}

else if(input(S1)&&!input(S2))
{
flag=1; //switch logic changes, so flag value changes to represent 1st gear
return flag;
}
}


int third_gear() //can u-shift to fourth or down-shift to third or remain same
{
if(!input(S1)&&input(S2))
{
flag=3; // no change in switches, so no change in flag value
return flag;
}

else if(!input(S1)&&!input(S2))
{
flag=4; //switch logic changes, so flag value changes to represent 4th gear
return flag;
}

else if(!input(S1)&&input(S2))
{
flag=2;//switch logic changes, so flag value changes to represent 2nd gear
return flag;
}
}


int fourth_gear() // can remain same or down-shift to 3rd
{
if(!input(S1)&&!input(S2))
{
flag=4; // no change in switches, so no change in flag value
return flag;
}

else if(input(S1)&&!input(S2))
{
flag=3; //switch logic changes, so flag value changes to represent 3rd gear
return flag;
}
}



int gear() //for identifying the flag value
{
int r;

if(flag==0) //the previous flag value is checked for neutral gear
{
r=neutral_gear(); //check for change in flag value in neutral gear
return r;
}

else if(flag==1)
{
r=first_gear(); //check for change in flag value in from 1st gear
return r;
}

else if(flag==2)
{
r=second_gear(); //check for change in flag value in 2nd gear
return r;
}

else if(flag==3)
{
r=third_gear(); //check for change in flag value in 3rd gear
return r;
}

else if(flag==4)
{
r=fourth_gear(); //check for change in flag value in 4th gear
return r;
}
}

void main()
{

setup_adc_ports(NO_ANALOGS);
setup_adc(ADC_CLOCK_DIV_2);
setup_psp(PSP_DISABLED);
setup_spi(SPI_SS_DISABLED);
setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
setup_timer_1(T1_DISABLED);
setup_timer_2(T2_DISABLED,0,1);
setup_comparator(NC_NC_NC_NC);
setup_vref(FALSE);

while(1)
{
int g;
g=gear(); //for checking the flag value
if(g==0)
{
output_high(NEUTRAL); //if flag is zero
}
else if(g==1)
{
output_high(FIRST); //if flag is one-first gear
}
else if(g==2)
{
output_high(SECOND); //if flag is two-second gear
}
else if(g==3)
{
output_high(THIRD); //if flag is three-third gear
}
else if(g==4)
{
output_high(FOURTH); //if flag is four-fourth gear
}
}
}


-I have used a global variable for the gear position.
-The logic is to check the switch logic states at each gear position.
-I have placed these switches in such a way when if a downshift occurs a switch is pressed, the same for the up-shift also.
-The switches are reset when again a up-shift or down-shift occurs.
-So I have to use separate functions for each gear position to find out the gear in use

[asmboy]

learn to use the code function.

[Mike Walne]

Use the code function, it preserves indentation so that logic flow is easier to follow.

Your code looks far too complex.

Explain exactly (in simple terms) what you want to happen.

Explain what each function is doing.

You've got several similar functions, they can probably be reduced to one (simpler) function.

From what I can see all your LEDs will glow eventually because you never turn them off!.

Mike

[[email protected]]

Sorry...
I have edited my post with code function.

[Ttelmah]

Several little comments:
1) setup_spi(SPI_SS_DISABLED);
This turns off slave select. It doesn't disable the slave. Correct syntax is:

setup_SPI(FALSE);

2) You make the common error of assuming switches switch!. Gernally, most forms of switch exhibit _bounce_. They will make and break several times for one operation. At the speed a processor works, you could possibly cycle through all the gears for one switch operation....

3) How are the switches wired?. Pull up resistors?.

4) Hopefully you have got current limiting resistors on the LED's?.

Instead of having all these separate gear routines, have a single variable (possibly an enum), for the gears. Have a keyscan routine, which returns a value (say) 0 for no change, '1' for change up, and '2' for change down. This can check the buttons a few times, and verify the switches are stably in the state, before returning the number. Then just a single routine, and if '1' is seen, it increments the gear number (if this is less than the highest allowed). If '2' it decrements (again if this is above the minimum). Nothing else.

Best Wishes

[Mike Walne]

Now I'm even more confused.

I'd hoped for a simple explanation.

My two-wheeler had a neutral between all the gears!

How does your system know which gear it's in at switch on?

Mike

[temtronic]

Don't feel too bad Mike...I'm confused as to what a '2 wheeler' is as there's only 4 speeds involved. One of my bicycles had 3 speeds the other 18....
So I'd like to know what '2 wheeler' is....
Also not sure why DPDT switches are used since you can decode 4 unique positions with just 2 switches.00,01,10,11
Or am I missing something else??
In any event 'debouncing' must be dealt with.
Original program is way too complicated...

[Ttelmah]

No, I don't think you are missing anything....

That is why I asked how the switches are wired. I _think_ he has possibly got the one pole of each switch wires to to supply at one side, and ground at the other, with the wiper going to the PIC pin. One switch is 'up', and the other 'down'. Possibly they are also spring biased. What the second pole is for I haven't got a clue!. I think he is trying to do some sort of electrical gearchange, like the paddle shift on some cars. I did a system like this for a child's electric car I made a little while ago.

Best Wishes

[[email protected]]

-Usually a encoder type sensor is used for this purpose in bikes.
-I cannot use that in my bike as it costs high and also not posiible to mount.

-Yes...the code here is complicated as I have used two DPDT switches.

-This is just a part of a the main program. I have to include
codes for 4 sensors, GPS, GSM and a RTC. So the program is going to have large no. of lines.

-Initially I thought of using simple "reset" switches. Than i jumped from this thinking that the controller will not be able to scan the rise signal due to large scanning time. So I choose DPDT switches which will have one position set or reset during gear shift.

-As said I think this can be implemented using simple programming logic. But my doubt is whether the same for eg. if(input(S1) code can be used for scanning the inputs for a momentary rise signal.

[ezflyr]

Hi,

Seriously, you need to tell us a lot more about how your system
works! You can start by telling us a bit about the mechanics of your shifter. Is
the shift pattern something like N-1-2-3-4? Can you only 'upshift' in a linear
pattern, and 'downshift' the same way? Now, what specifically do your
switches do under all circumstances? What is the output, for instance, in 'N'?
What happens to the switch outputs when you upshift from 'N' to '1', etc.?
You have to provide a lot more information about the sequence of events,
and the expected switch response to these events if you have any hope of
getting help here!

John

[Mike Walne]

Please:-

1) Don't edit code after you've had a response. It makes nonsense of intelligent replies.
2) Learn to use the code button.
3) Provide a schematic.
4) Describe what happens to the switch-states on a gear change.
5) Provide as much other information as you can so that we can help you.
6) Explain why it is necessary to have a DPDT switch. Your code only calls for SPDT, or maybe even SPST.

At this stage, none of us have anything to work on.

Mike

[[email protected]]

[ckielstra]

Your new code is a lot easier to understand. Easier means less errors. Congratulations.

When you switch gears, how long do you estimate the switch will be activated?
Considering all mechanics behind the manual gear shifter I guess it will be a few hundredths of milliseconds at a minimum and most likely a lot longer.
Now, looking at your code running at 20MHz, how long do you think it will take to run 1 cycle where the switch is tested and the LEDs are updated? You got a feeling what I'm hinting at?

Then another problem is that you have no prevention against overflow and underflow. Now you can switch up to the 255th gear if you want to.

Here is a stupid copy/paste error:

[ezflyr]

Hi,

Frankly I don't see how this is ever going to work reliably. Since there is no
unique set of conditions for each gear, what happens if/when the mechanics
and the code loses sync? For instance a switch closure is missed, or the PIC
restarts? For that matter, what happens when the code starts running, and
the gear shift is not in the expected position?

I'm sure that OEM shift indicator systems use a more sophisticated sensing
arrangement. I'm not really sure what you'd do after the fact?

John

[gpsmikey]

If you are using the switches to count "up" and "down" as it looks like you are, there are two problems - the first is as another pointed out, when they get out of sync - the second (which basically insures the first happens) is the switches need to be very thoroughly de-bounced or each time one closes you may get 20 or 30 counts (almost all mechanical switches bounce multiple times when they close). You may well also see bounces if you are riding on rough terrain.
_________________
mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3