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masterchief
Guest
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| getc problem |
 Posted: Sat Jan 08, 2005 1:34 pm |
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I did a little test program.
| Code: | | #use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8) |
| Code: | void main()
{
int flag;
int ch;
flag = 1;
while(1) {
ch = getc();
if (flag) {
output_high(PIN_A1);
flag = 0;
} else {
output_low(PIN_A1);
flag = 1;
}
printf("You pressed ");
putc ( ch );
printf(" ");
}
} |
before I press any key, the LED is off as it should be. When I press a key, the LED is on, but the problem is that it stays on all the time, even when I press keys.
This means that the program is stuck at the line
Why is it??? |
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Darren Rook
Joined: 06 Sep 2003
Posts: 287
Location: Milwaukee, WI
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| Posted: Sat Jan 08, 2005 2:17 pm |
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Try adding
| Code: | | setup_adc_ports( NO_ANALOGS ); |
At the beginning of your code.
Or use a port that isn't an analog port for the LED. |
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Guest
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| Posted: Sat Jan 08, 2005 3:27 pm |
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| This does not solve anything. even by changing the port, the program still seems to be stuck at the line ch = getc() |
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rwyoung
Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA
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| Posted: Sat Jan 08, 2005 4:22 pm |
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Tested with V3.215 on PIC16F877A and it seems to be working just fine. Pin A1 goes up and down (per DMM, didn't hook up LED) and RS232 port is echoing typed character.
Note that I added 4 lines to what you had in your post:
#include <pic16f877a.h>, #case, #use delay and the #fuse statement.
Below is a copy of the LST file.
What version of the compiler are you using? What chip are you using?
| Code: | CCS PCM C Compiler, Version 3.215, 26886 08-Jan-05 16:15
Filename: C:\Program Files\PICC\Projects\crapola\crapola.LST
ROM used: 90 words (1%)
Largest free fragment is 2048
RAM used: 8 (5%) at main() level
8 (5%) worst case
Stack: 1 locations
*
0000: MOVLW 00
0001: MOVWF 0A
0002: GOTO 015
0003: NOP
.................... #include <16F877A.h>
.................... //////// Standard Header file for the PIC16F877A device ////////////////
.................... #device PIC16F877A
.................... #list
....................
.................... #case
.................... #use delay(clock=20000000)
.................... #fuses NOWDT,HS, PUT, NOPROTECT, NODEBUG, BROWNOUT, NOLVP, NOCPD, NOWRT
.................... #use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8)
....................
.................... void main()
.................... {
0015: CLRF 04
0016: MOVLW 1F
0017: ANDWF 03,F
0018: BSF 03.5
0019: BSF 1F.0
001A: BSF 1F.1
001B: BSF 1F.2
001C: BCF 1F.3
001D: MOVLW 07
001E: MOVWF 1C
001F: MOVF 1C,W
0020: BCF 03.5
0021: BCF 0D.6
0022: MOVLW 81
0023: BSF 03.5
0024: MOVWF 19
0025: MOVLW 26
0026: MOVWF 18
0027: MOVLW 90
0028: BCF 03.5
0029: MOVWF 18
.................... int flag;
.................... int ch;
.................... flag = 1;
002A: MOVLW 01
002B: MOVWF 21
....................
.................... while(1) {
....................
.................... ch = getc();
002C: BTFSS 0C.5
002D: GOTO 02C
002E: MOVF 1A,W
002F: MOVWF 22
....................
.................... if (flag) {
0030: MOVF 21,F
0031: BTFSC 03.2
0032: GOTO 039
.................... output_high(PIN_A1);
0033: BSF 03.5
0034: BCF 05.1
0035: BCF 03.5
0036: BSF 05.1
.................... flag = 0;
0037: CLRF 21
.................... } else {
0038: GOTO 03F
.................... output_low(PIN_A1);
0039: BSF 03.5
003A: BCF 05.1
003B: BCF 03.5
003C: BCF 05.1
.................... flag = 1;
003D: MOVLW 01
003E: MOVWF 21
.................... }
....................
.................... printf("You pressed ");
003F: CLRF 23
0040: MOVF 23,W
0041: CALL 004
0042: INCF 23,F
0043: MOVWF 77
0044: MOVF 77,W
0045: BTFSS 0C.4
0046: GOTO 045
0047: MOVWF 19
0048: MOVLW 0C
0049: SUBWF 23,W
004A: BTFSS 03.2
004B: GOTO 040
.................... putc ( ch );
004C: MOVF 22,W
004D: BTFSS 0C.4
004E: GOTO 04D
004F: MOVWF 19
.................... printf(" ");
0050: MOVLW 20
0051: BTFSS 0C.4
0052: GOTO 051
0053: MOVWF 19
0054: MOVLW 20
0055: BTFSS 0C.4
0056: GOTO 055
0057: MOVWF 19
.................... }
0058: GOTO 02C
.................... }
....................
0059: SLEEP
Configuration Fuses:
Word 1: 3F72 HS NOWDT PUT NODEBUG NOPROTECT BROWNOUT NOLVP NOCPD NOWRT
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_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month! |
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Guest
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| Posted: Sat Jan 08, 2005 4:29 pm |
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I realized that the problem is my circuit. when I send data from the PIC, everything works fine. When the PC sends data, the PIC seems not to receive the data. (The pic gets 0x00 for any character)
I also realized that when I power down my circuit, as the voltage is decreasing, If I keep pressing keys, the PIC echoes the characters that I press for about half a second before completely powering down.
The problem might be with the capacitors that I am using.
Here is how my MAX232 is hooked up:
PIN 1 and 3 are connected through a 10uF cap
PIN 4 and 5 are connected through a 10uF cap
PIN 6 is connected to ground through a 20uF cap
PIN 2 is connected to 5V through a 20uF cap
other tx and rx pins are correctly connected.
What do you think? |
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drh
Joined: 12 Jul 2004
Posts: 192
Location: Hemet, California USA
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| Posted: Sat Jan 08, 2005 6:37 pm |
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Double check the polarity of the capacitors.
_________________
David |
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Guest
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| masterchief |
| Posted: Sat Jan 08, 2005 6:56 pm |
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| I am using ceramic disc capacitors, they don't have polarity. So, the problem is probably somewhere else... |
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Guest
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| masterchief |
| Posted: Sat Jan 08, 2005 10:03 pm |
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Before I press anything, the pin R2out (TTL) of the MAX232 chip that goes to the rx pin on the chip is high (5V).
When I press a key, the pin goes and stays to zero. Besides, the terminal shows me "You pressed ". there is no key code, The PIC just receives a 0x00 iinstead of the keycode.
Is this behavior normal, I dont think so.
Any suggestions? Thanks in advance |
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dyeatman
Joined: 06 Sep 2003
Posts: 1933
Location: Norman, OK
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| Sounds like a MAX232 problem |
| Posted: Sat Jan 08, 2005 10:18 pm |
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The MAX232 (R2out) output should return to the original high state after the character(s) come in.
What does the input pin on the MAX232 do? Does it return to low when the incoming char(s) are complete?
Since there is no enable on this chip the input and output states MUST ALWAYS be opposite (i.e if input R2in high then the output R2out must be low). If they are ever the same something is definitely wrong and I would suspect a wiring error since it seems to start out properly.
Check all the connections making sure all the caps, especially the ones to pins 2 and 6, are wired properly. |
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Guest
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| masterchief |
| Posted: Sat Jan 08, 2005 11:03 pm |
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the voltage on pin R2IN is about -10.5V
while the voltage on pin R2OUT is 0 |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat Jan 08, 2005 11:18 pm |
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| Quote: | I am using ceramic disc capacitors
PIN 1 and 3 are connected through a 10uF cap
PIN 4 and 5 are connected through a 10uF cap
PIN 6 is connected to ground through a 20uF cap
PIN 2 is connected to 5V through a 20uF cap |
To my knowledge, ceramic disk capacitors are not
available in the uF range. They are only available
in the pf or nF range. Are you certain that your
capacitors are 10uF, etc. ? |
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kender
Joined: 09 Aug 2004
Posts: 768
Location: Silicon Valley
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| Posted: Sat Jan 08, 2005 11:28 pm |
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MAX232 datasheet suggest to use 0.1uF to 1.0uF (page 17). I always use 0.1uF caps with MAX232 myself.
Oh, by the way, in your test circuit do you sink or source current from/to the LED?
Nick |
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Guest
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| Posted: Sat Jan 08, 2005 11:29 pm |
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That was my problem. I was dealing with picofarads instead of micro farads.
Thank you very much. I lack experience, but I am gaining it with people like you.
Thank you to all the people who helped |
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