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Guest
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| Strange I/O Behaviour..... |
 Posted: Tue Dec 19, 2006 5:09 pm |
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Hi,
I have a project that uses a couple of pushbuttons connected to individual I/O pins. I recently changed from a 16F628 to a 16F819 because I needed an A/D channel, but now one of my buttons is not working properly. I have reduced the problem to a simple test program shown below:
| Code: |
#include <16f628.h>
#fuses XT, NOWDT, NOPROTECT, NOLVP, BROWNOUT
//-----< Compiler use statements >-----
// Tell compiler clock speed is 4.00 MHZ Crystal
#use delay(clock=4000000)
//-----< General Program Defines >-----
#define Tx_Out PIN_B3 // serial data transmit pin to PC
#define Inc_Btn PIN_A3 // Increment button
#define Dec_Btn PIN_B5 // Decrement button
//-----< Serial Port Definition >-----
#use rs232(baud=9600, xmit=Tx_Out)
void main(void)
{
printf("At the top... \n\r");
while(1)
{
if (!input(Inc_Btn))
{
delay_ms(150);
printf("Incrementing\n\r");
while (!input(Inc_Btn));
}
if (!input(Dec_Btn))
{
delay_ms(150);
printf("Decrementing\n\r");
while (!input(Dec_Btn));
}
} // while
} // end Main
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When I run this code using a 16F628 it works as expected, and I see the following on HyperTerminal:
At the top...
Incrementing <---- Increment Button Pushed
Decrementing <---- Decrement Button Pushed
When I run this code using a 16F819 it does not work as expected, and I see the following on HyperTerminal:
At the top...
At the top...
Incrementing <---- Increment Button Pushed
Decrementing <---- Decrement Button Pushed
Notice that when the Increment button is pushed, the code seems to restart from the top, but this does not happen with the Decrement button.
Is something associated with input pin A3 causing this to happen on the 16F819? If so, I can't figure it out!
Compiler is 3.249
Thanks,
Charlie |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Dec 19, 2006 5:48 pm |
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The 16F819 has a lot of flaky erratas on the i/o pins.
A4 silicon errata:
http://ww1.microchip.com/downloads/en/DeviceDoc/80159f.pdf
B0 silicon errata:
http://ww1.microchip.com/downloads/en/DeviceDoc/80212c.pdf
I looked at the .LST file code, and it's setting up Port A as all digital.
That part is correct.
On the A4 errata, where the chip resets if you do almost anything
to the PGM pin (pin B3) -- this could be the problem.
Try using a different pin for your RS232 output. Configure pin RB3
to be a high-level output pin. Make sure the NOLVP fuse is enabled.
| Code: | | output_high(PIN_B3); |
This would help to tell if the problem is due to the pin B3 errata.
The ports on this PIC are still so flaky, even with the B0 errata, that
I would just go use another chip. |
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Guest
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| Posted: Wed Dec 20, 2006 7:26 pm |
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Hi PCM,
Thanks for the reply! I moved the Tx to another pin and set B3 high as you suggested, but no luck on solving the problem  I then moved my 'Increment' pushbutton to a different pin, and that solved the problem  !
I'll probably change chips for the final version of my project, but at least these changes will allow me to continue coding until I can do that!
Thanks again!
Charlie |
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