![](templates/subSilver/images/CCSLogo.jpg) |
![CCS C Software and Maintenance Offers](templates/subSilver/images/forumAd6.jpg) |
View previous topic :: View next topic |
Author |
Message |
jet_pack234
Joined: 11 Feb 2005 Posts: 11
|
inputs on 16F628 |
Posted: Mon Feb 21, 2005 8:17 pm |
|
|
Hi,
I am able to send a string via RS232, but when I try and read portA inputs and send the corresponding value I get garbage. I had a look at the data sheet and the inputs are designated as schmitt trigger inputs. What does this mean exactly. I have been using an 8 way dip switch which puts the supply voltage onto each of the Porta input pins. Perhaps this is wrong???
#include <16f628.h>
#fuses INTRC_IO,NOWDT,NOPROTECT,NOLVP,NOBROWNOUT,NOMCLR
#use delay(clock=4000000) //clock rate in Hz
#use rs232(baud=9600, xmit=PIN_B2,rcv=PIN_B1)
int8 data;
void main() {
setup_uart (TRUE);
SET_TRIS_A( 0b11111111);
puts("Go");
while (TRUE) {
output_high(PIN_B4);
delay_ms(100);
output_low(PIN_B4);
delay_ms(500);
data = input_A();
putc(data);
delay_ms(100);
}
While(TRUE);
} |
|
![](templates/subSilver/images/spacer.gif) |
PCM programmer
Joined: 06 Sep 2003 Posts: 21708
|
|
Posted: Mon Feb 21, 2005 8:43 pm |
|
|
Quote: | I have been using an 8 way dip switch which puts the supply
voltage onto each of the Porta input pins. Perhaps this is wrong??? |
The standard method is to put pull-up resistors on the PIC input pins,
and then connect each pin to a DIP switch section. The other side
of the DIP switches all go to ground.
Look at this schematic. He has 1K pullup resistors on RA0-RA2.
Each pin also goes to a switch, and the other side of the switches
go to ground. You don't need to use 1K. I would have used 4.7K
or 10K resistors.
http://www.vermontficks.org/pellets.gif
If you want extra safety, you can put a series resistor between
the PIC pin and the pullup and DIP switch. This prevents you
from accidently shorting the output driver of the PIC to ground,
in case you configure the pin as an output instead of an input,
as you intended. The 470 ohm series resistor limits the current
so the output driver won't be damaged. This is a good idea in
a board designed for students.
Look at the schematic on page 19 of the PicDem2-Plus manual
at the "40-pin Device", at pin RA4 to see this:
http://ww1.microchip.com/downloads/en/DeviceDoc/51275b.pdf |
|
![](templates/subSilver/images/spacer.gif) |
|
|
You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|