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ds
Joined: 01 Nov 2009
Posts: 15
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| Serial Port Funny Business |
 Posted: Fri Mar 26, 2010 9:20 pm |
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Hi all,
So I got my PIC16F688 talking to my computer via serial port! Yay!! For a test I have made a simple program to turn a led on and off at 500ms intervals. Depending on where I put the printf statements, the programs works and blinks the led at the correct timing...or it flickers the led but sends the LED on / off statement to the computer with the correct timing.
Here is the first version that doesn't work:
| Code: |
#include <16F887.h>
#fuses INTRC_IO,NOWDT,PUT,NOMCLR,NOPROTECT,NOCPD,NOBROWNOUT,NOIESO,NOFCMEN
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C4, rcv=PIN_C5,ERRORS,PARITY=N,)
void main()
{
while(1){
delay_ms(500);
output_high(PIN_C0);
printf("\r\nLED On\r\n");
delay_ms(500);
output_low(PIN_C0);
printf("\r\nLED Off\r\n");
}
}
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and the second version which does work:
| Code: |
#include <16F887.h>
#fuses INTRC_IO,NOWDT,PUT,NOMCLR,NOPROTECT,NOCPD,NOBROWNOUT,NOIESO,NOFCMEN
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C4, rcv=PIN_C5,ERRORS,PARITY=N,)
void main()
{
while(1){
delay_ms(500);
printf("\r\nLED On\r\n");
output_high(PIN_C0);
delay_ms(500);
printf("\r\nLED Off\r\n");
output_low(PIN_C0);
}
}
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As you can see... all that I have done is put the printf before the pin output statement as opposed to after the output statement.
Can anyone tell me what is going on here?
Thanks!
DS. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Mar 26, 2010 9:46 pm |
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Post your compiler version.
| Quote: |
So I got my PIC16F688 talking to my computer via serial port
#include <16F887.h>
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Confirm which PIC you are using. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19552
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| Posted: Sat Mar 27, 2010 4:08 pm |
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It actually sounds like RMW.
It appears that he is using a software serial port, and as such, this will need to read/write portC. I'd suspect that the LED circuit, is slightly overloading the PIC pin, and when the serial I/O takes place, the LED output, is read as low, and therefore turned off.
Do a search here on the term 'RMW', and try a larger series resistor feeding the LED.
Best Wishes |
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