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PIC18F452, chip interfering with DIP switch

Started by scubagreg7777777 ●December 4, 2004


Hi everyone,

I'm pretty new to PICS, but will do my best to characterize my problem
and provide as much pertinent info as possible. I perplexed as to
what is going on with my PIC. I am using an 18f452 on a PICDEM 2 Plus
board, and my own PCB that I milled.

Here is the problem:

I have a 4-bit, high asserting DIP switch, with its input being sent
to PORTC.RC1 through PORTC.RC4.

Using an oscilliscope on the output I can observe that the switch is
indeed workin, switching from ~0v to ~5v. However, as soon as I plug
the PIC18F452 into the board, the DIP switch no longer responds (still
viewing the output on a scope), and stays a flat ~0v, regardless of
how the DIP is asserted. As soon as I pop the chip out, the switch
is back to normal, and switches from 0v to 5v.

Furthermore, If I touch a PORTC pin with a 5v connection, the software
behaves how it should, and outputs on PORTD. It seems that the DIP
switches simply stop working.

I am using a 160ohm resistor, and there isn't too much else about my
setup. I have been able to repeat this behaviour on both the PICDEM 2
Plus board, and my own PCB. Below is a picture of my setup, and I
have attached a copy of my code (using MCC18 compiled with MPLAB 6.4).

I have switched out PICS, but not resistors (they're soldered in, and
I do not have access to a soldering kit right now.

What really baffles me, is that as soon as I put my chip in, the
switch dies, and no longer works. If anyone has suggestions, PLEASE
let me know.

(also, as a bonus, if someone could explain why this is happening, I
would be very interested in learning how to fix this problem, and why
it happened)

Thanks in advance,

Greg (DIP setup)

5v
|
|
/
\
/ (160 ohm resistor)
\
|
|--------- output to PORTC
|

/
/ (switch)
/
|
|
|
----- (ground)
--

Code:
--------

/* Include Libraries */
#include <p18f452.h> /* for TRISB and PORTB declarations */
#include <adc.h> /* A/D library */
#include <stdlib.h> /* Standard Library */ /**********************************************/
/* Function Prototypes */

int checkSpeed( void );
int checkDip( void ); /***********************************************/
/* Variable Declaration */
/* */

/* main() */
int temp = 0; // temp variabe used in checkSpeed()
int test = 0; // test variable used in main to determine if Ra1 is
detecting high load (temp)

int dipVal = 0; // value returned from checkDip() function call
int speedVal = 0; // speed setting returned from checkSpeed()
function call
int onTime = 0; // max amount of time a particular channel/light
can be turned on
int offTime = 0; // amount of time a channel/light will be turned off
int delayCounter = 0; // counter variable, useed in output
display engine for on and off time
int speedCounter = 1; // used in nested loop to get around max
numeric value -- full explanation in dev notes
int curOutput = 1; // current chanel being output /* checkSpeed() */
int a2dSpeed = 0 ; // value obtained from a2d conversion
int userInputSpeed = 0; // speed setting, inferred from a2dSpeed
value, returned to main
// 1 = slow, 2 = medium, 3 = fast /* checkDip() */
int inputSum = 0; // final, base-10 value of user input via DIP /* customLight() */ /* delay() */
int i = 0; // counter, used for delay loop
int j = 1; // counter, used for number of loops -- speed control

void main( void )
{

/* Initialize Configuration */
TRISA = 1; // configs PORTA for INPUT -- used for checkSpeed()
TRISC = 1; // configs PORTC for INPUT -- used for checkDip()
TRISD = 0; // configs PORTD for OUTPUT -- used for light output
/* configure A/D convertors */
/* detailled explanation is located at: p 16-18 in
MPLAB-C18-Libraries.pdf */
/* ADC_FOSC_32 -> a/d clock source uses FOSC/32
ADC_RIGHT_JUST -> result in least significant bits
ADC_8ANA_0REF -> VREF+ = Vdd and VREF- = Vss (both analog)
ADC_CH# -> the channel being used
ADC_INT_OFF -> disable interrupts */

/* ADC_CH0 -> speed */
OpenADC( ADC_FOSC_32 & ADC_RIGHT_JUST & ADC_8ANA_0REF,ADC_CH0 &
ADC_INT_OFF ); /* checkSpeed() */ /* main program */
while(1)
{

/* (re)initialize values */
speedVal = 0;
dipVal = 0; /* obtain user input */
dipVal = checkDip(); // determine DIP setting

if(dipVal == 0)
PORTD = 0;

if(dipVal == 1)
{
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
}

if(dipVal == 2)
{
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
}

if(dipVal == 3)
{
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;

PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;

PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
} if(dipVal == 4)
{
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;

PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;

PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;

PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
}

if(dipVal == 5)
{
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;

PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 1;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;
PORTD = 0;
while(speedVal < 24000) speedVal++;
while(speedVal > 3) speedVal--;

}

/* reset */
PORTD = 0;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;
speedVal = 0; while(speedVal < 24000) speedVal++;

} /* end while(1) */ } /* end main() */

/***************************************************
Function: checkSpeed()
Arguments: none
Return: int userInputSpeed -> digitized value of user's speed selection
(1 = slow, 2 = medium, 3 = fast)
I/O Pins Used: PORTA -> RA0

Description: checkSpeed() checks PORTA.RA0 and through a series of if
statements,
converts the voltage into one of 3 values and returns this
value
****************************************************/
int checkSpeed ( void)
{

/* AtoD Conversion */
/* CloseADC() is not used, as nowhere in the MCC18 libraries
documentation, or PIC18F452 datasheet
does it suggest leaving an A/D converter on is harmful or
discouraged. Opening the A/D converter
once (in main()'s init period, and leaving it open saves some
computational time
*/
SetChanADC( ADC_CH0 ); // Open channel 0

/* research timing constraings when using SetChanADC function call */
/* p187 - 188 in pic18f452 datasheet */
while(temp < 1200) // temporary solution
temp++;

ConvertADC(); // Start conversion
while( BusyADC() ); // Wait for completion
a2dSpeed = ReadADC(); // Read result /* The PICDEM 2 PLUS board has a 5k pot in series with a 470 ohm resistor.
The range detected by the A/D convertor is 0x000 to 0x3FF. In base10
this range is 0 to 1023. Therefore, the A/D conversion is broken up
into 3 groups, with threshold points at 341, 682, and 1023.
(1023/3 = 341)
(1 signifies slow / 2 signifies medium / 3 signifies fast)
*/ /* Interpret a2d value into slow/medium/fast speed */
if( a2dSpeed <= 341) // slow setting
userInputSpeed = 1;
else if( (a2dSpeed <= 682) && (a2dSpeed >= 342) ) // medium setting
userInputSpeed = 2;
else if ( (a2dSpeed <= 1023) && (a2dSpeed >= 683) ) // fast setting
userInputSpeed = 3;
else
userInputSpeed = -1; // signifies error w/ a2d conversion return userInputSpeed; /* return obtained value */

} /* end checkSpeed() */ /***************************************************
Function: checkDip()
Arguments: none
Return: int inputSum -> base ten digitized value of user's DIP switch
selection
I/O Pins Used: PORTC -> RC1, RC2, RC3, RC4

Description: checkDip() uses checks pins RC1 through RC4 for high or
low voltages.
Then, through a series of if statements, assigns a corrosponding base
10 value to inputSum and returns this number
****************************************************/
int checkDip( void )
{

/* (re)initialize variables to avoid potential troubles */
inputSum = 0; // final, digital, value of DIP switch, returned
to main() /* note that ports RC1 through RC4 are used */
/* Rc1 is connected to the least significant DIP switch */
/* Rc4 is connected to the most significant DIP switch */

if( PORTCbits.RC1 == 1) // ensure Rc1 (pin #16) is connected to
least significant bit ofDIP switch
inputSum = inputSum + 1;

if( PORTCbits.RC2 == 1) // ensure Rc2 (pin #17) is connected to 2nd
lowest bit of DIP switch
inputSum = inputSum + 2;

if( PORTCbits.RC3 == 1) // ensure Rc3 (pin #18) is connected to
3rd lowest bit of DIP switch
inputSum = inputSum + 4;

if( PORTCbits.RC4 == 1) // ensure Rc4 (pin #23) is connected to
4th lowest bit of DIP switch
inputSum = inputSum + 8; return inputSum; // return value

} /* end checkDip() function call */


Reply by Chad Russel ●December 4, 20042004-12-04
Yahoo mail is coming slow again. I don't do C, but from what I can
see, I think your problem is the TRIS settings. Each bit of the port
is set with TRIS, not the entire port. Therefore setting TRISB = 1
sets bit 0 to input and bits 1-7 to outputs. If you want bits 1-4 as
inputs and the rest outputs the value would be b'00011110', 1Eh, or 30
decimal.

Good luck,
Chad
--- scubagreg7777777 <> wrote:

>
>
> Hi everyone,
>
> I'm pretty new to PICS, but will do my best to characterize my
> problem
> and provide as much pertinent info as possible. I perplexed as to
> what is going on with my PIC. I am using an 18f452 on a PICDEM 2
> Plus
> board, and my own PCB that I milled.
>
> Here is the problem:
>
> I have a 4-bit, high asserting DIP switch, with its input being sent
> to PORTC.RC1 through PORTC.RC4.
>
> Using an oscilliscope on the output I can observe that the switch is
> indeed workin, switching from ~0v to ~5v. However, as soon as I plug
> the PIC18F452 into the board, the DIP switch no longer responds
> (still
> viewing the output on a scope), and stays a flat ~0v, regardless of
> how the DIP is asserted. As soon as I pop the chip out, the switch
> is back to normal, and switches from 0v to 5v.
>
> Furthermore, If I touch a PORTC pin with a 5v connection, the
> software
> behaves how it should, and outputs on PORTD. It seems that the DIP
> switches simply stop working.
>
> I am using a 160ohm resistor, and there isn't too much else about my
> setup. I have been able to repeat this behaviour on both the PICDEM
> 2
> Plus board, and my own PCB. Below is a picture of my setup, and I
> have attached a copy of my code (using MCC18 compiled with MPLAB
> 6.4).
>
> I have switched out PICS, but not resistors (they're soldered in, and
> I do not have access to a soldering kit right now.
>
> What really baffles me, is that as soon as I put my chip in, the
> switch dies, and no longer works. If anyone has suggestions, PLEASE
> let me know.
>
> (also, as a bonus, if someone could explain why this is happening, I
> would be very interested in learning how to fix this problem, and why
> it happened)
>
> Thanks in advance,
>
> Greg > (DIP setup)
>
> 5v
> |
> |
> /
> \
> / (160 ohm resistor)
> \
> |
> |--------- output to PORTC
> |
>
> /
> / (switch)
> /
> |
> |
> |
> ----- (ground)
> -- >
>
> Code:
> --------
>
> /* Include Libraries */
> #include <p18f452.h> /* for TRISB and PORTB declarations */
> #include <adc.h> /* A/D library */
> #include <stdlib.h> /* Standard Library */ > /**********************************************/
> /* Function Prototypes */
>
> int checkSpeed( void );
> int checkDip( void ); > /***********************************************/
> /* Variable Declaration */
> /* */
>
> /* main() */
> int temp = 0; // temp variabe used in checkSpeed()
> int test = 0; // test variable used in main to determine if Ra1 is
> detecting high load (temp)
>
> int dipVal = 0; // value returned from checkDip() function
> call
> int speedVal = 0; // speed setting returned from checkSpeed()
> function call
> int onTime = 0; // max amount of time a particular channel/light
> can be turned on
> int offTime = 0; // amount of time a channel/light will be turned
> off
> int delayCounter = 0; // counter variable, useed in output
> display engine for on and off time
> int speedCounter = 1; // used in nested loop to get around max
> numeric value -- full explanation in dev notes
> int curOutput = 1; // current chanel being output > /* checkSpeed() */
> int a2dSpeed = 0 ; // value obtained from a2d conversion
> int userInputSpeed = 0; // speed setting, inferred from a2dSpeed
> value, returned to main
> // 1 = slow, 2 = medium, 3 = fast > /* checkDip() */
> int inputSum = 0; // final, base-10 value of user input via DIP > /* customLight() */ > /* delay() */
> int i = 0; // counter, used for delay loop
> int j = 1; // counter, used for number of loops -- speed control
>
> void main( void )
> {
>
> /* Initialize Configuration */
> TRISA = 1; // configs PORTA for INPUT -- used for checkSpeed()
> TRISC = 1; // configs PORTC for INPUT -- used for checkDip()
> TRISD = 0; // configs PORTD for OUTPUT -- used for light output >
> /* configure A/D convertors */
> /* detailled explanation is located at: p 16-18 in
> MPLAB-C18-Libraries.pdf */
> /* ADC_FOSC_32 -> a/d clock source uses FOSC/32
> ADC_RIGHT_JUST -> result in least significant bits
> ADC_8ANA_0REF -> VREF+ = Vdd and VREF- = Vss (both analog)
> ADC_CH# -> the channel being used
> ADC_INT_OFF -> disable interrupts */
>
> /* ADC_CH0 -> speed */
> OpenADC( ADC_FOSC_32 & ADC_RIGHT_JUST & ADC_8ANA_0REF,ADC_CH0 &
> ADC_INT_OFF ); /* checkSpeed() */ > /* main program */
> while(1)
> {
>
> /* (re)initialize values */
> speedVal = 0;
> dipVal = 0; > /* obtain user input */
> dipVal = checkDip(); // determine DIP setting >
>
> if(dipVal == 0)
> PORTD = 0;
>
> if(dipVal == 1)
> {
> PORTD = 1;
> while(speedVal < 24000) speedVal++;
> while(speedVal > 3) speedVal--;
> PORTD = 0;
> }
>
> if(dipVal == 2)
> {
> PORTD = 1;
> while(speedVal < 24000) speedVal++;
> while(speedVal > 3) speedVal--;
> PORTD = 0;
> while(speedVal < 24000) speedVal++;
> while(speedVal > 3) speedVal--;
> PORTD = 1;
> while(speedVal < 24000) speedVal++;
> while(speedVal > 3) speedVal--;
> PORTD = 0;
> }
>
> if(dipVal == 3)
> {
>
=== message truncated === =====
My software has no bugs, only undocumented features.
__________________________________



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