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xav27
Guest
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| I/O pin management |
 Posted: Fri Apr 09, 2004 2:58 am |
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Hello,
I'm trying to use unused pin of my PIC to do 8 bit DATA bus I/O.
for example, if I have RA0,RA1,RA4,RB2,RB5,RB7,RC0,RC5 pin unused, how can I outpout/inpout a byte using this pin ?
0) is it possible ?
1) how to do correct pin affectation (something like a struct ????)
2) how to correctly set TRIS registers for read and write operation
Hope I'm clear enought ?!
Thanks in advance
Xavier |
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Haplo
Joined: 06 Sep 2003
Posts: 659
Location: Sydney, Australia
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| Posted: Fri Apr 09, 2004 3:43 am |
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| Of course it is possible. The best way to do it would be using structs. Look at the LCD.C file in the \drivers directory for more details. |
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Userrr
Joined: 09 Jul 2004
Posts: 40
Location: Europe
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| Haplo answered me |
| Posted: Fri Oct 15, 2004 1:31 pm |
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answered me:
this LCD.c struct
struct lcd_pin_map { // This structure is overlayed
BOOLEAN enable; // on to an I/O port to gain
BOOLEAN rs; // access to the LCD pins.
BOOLEAN rw; // The bits are allocated from
BOOLEAN unused; // low order up. ENABLE will
int data : 4; // be pin B0.
} lcd;
But how with 2 ports
CAN I Do something as it
struct port_new {
int1 PORTB.0;
int1 PORTB.1;
int1 PORTA.5;
int1 PORTA.6;
int1 PORTB.3;
int1 PORTB.5;
int1 PORTA.1;
int1 PORTA.0;
} ports;
how I must do it |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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Userrr
Joined: 09 Jul 2004
Posts: 40
Location: Europe
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| Thanks PCM Programmer |
| Posted: Fri Oct 15, 2004 3:05 pm |
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| Thanks PCM Programmer |
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Userrr
Joined: 09 Jul 2004
Posts: 40
Location: Europe
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| But |
| Posted: Fri Oct 15, 2004 3:21 pm |
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But here I can't get this:
PORTNEW=0xFF - function
and that is mean that as example
PORTA=0x0F and PORTB=0x0F
PORTNEW { RA0,RA1,RA2,RA3,RB0,RB1,RB2,RB3}
PCM programmer please answ. me |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Oct 15, 2004 5:30 pm |
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There are many ways to do it. It's a question of which way
is the most efficient. It's also a question of how much time
do you (or I) want to spend on it. Here is one way:
| Code: |
#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
// We want to be able to write a byte value to the following spare pins.
// RA0,RA1,RA4,RB2,RB5,RB7,RC0,RC5
// Define the bit addresses of the spare pins.
// The addresses shown below are for the 16F877.
#bit RA0 = 5.0
#bit RA1 = 5.1
#bit RA4 = 5.4
#bit RB2 = 6.2
#bit RB5 = 6.5
#bit RB7 = 6.7
#bit RC0 = 7.0
#bit RC5 = 7.5
// The following macro defines the "set_spare_bits()" function.
// This will be implemented by the compiler as eight sequential
// BSF or BCF instructions.
#define set_spare_bits(x) \
RA0 = x & 1; \
RA1 = (x >> 1) & 1; \
RA4 = (x >> 2) & 1; \
RB2 = (x >> 3) & 1; \
RB5 = (x >> 4) & 1; \
RB7 = (x >> 5) & 1; \
RC0 = (x >> 6) & 1; \
RC5 = (x >> 7) & 1
//==================================
void main()
{
// The TRIS must be set for the spare pins before the function is
// called. The spare pins must be set as outputs.
set_tris_a(0b11101100);
set_tris_b(0b01011011);
set_tris_c(0b11011110);
set_spare_bits(0x55);
while(1);
}
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The program above compiles to the following code:
| Code: |
0000 00309 ..... set_tris_a(0b11101100);
0014 30EC 00310 MOVLW EC
0015 1683 00311 BSF 03.5
0016 0085 00312 MOVWF 05
0000 00313 ..... set_tris_b(0b01011011);
0017 305B 00314 MOVLW 5B
0018 0086 00315 MOVWF 06
0000 00316 ..... set_tris_c(0b11011110);
0012 30FF 00317 MOVLW FF
0013 00A1 00318 MOVWF 21
0019 30DE 00319 MOVLW DE
001A 0087 00320 MOVWF 07
001B 1283 00321 BCF 03.5
001C 00A1 00322 MOVWF 21
0000 00323 .....
0000 00324 ..... set_spare_bits(0x55);
001D 1405 00325 BSF 05.0
001E 1085 00326 BCF 05.1
001F 1605 00327 BSF 05.4
0020 1106 00328 BCF 06.2
0021 1686 00329 BSF 06.5
0022 1386 00330 BCF 06.7
0023 1407 00331 BSF 07.0
0024 1287 00332 BCF 07.5 |
--------------
Edited to fix the mistake in the last line of the set_spare_bits()
macro, as noted in the post below.
Edited to put code in a Code Block.
Last edited by PCM programmer on Thu Apr 07, 2011 10:03 am; edited 3 times in total |
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aaaaamartin
Joined: 17 Apr 2005
Posts: 39
Location: Germany Stuttgart
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| Posted: Thu Dec 14, 2006 1:43 pm |
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Hello,
what if I need input and output ?
Regards Martin |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Dec 14, 2006 5:00 pm |
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| Quote: | | what if I need input and output ? |
The demo program below shows how to read eight spare bits and pack
them into a byte variable.
You don't need to set the TRIS if you're running the compiler in Standard
i/o mode. The compiler will handle it, since I'm using CCS i/o functions
in the macro. ("Standard i/o" mode is the default mode of the compiler).
| Code: | #include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
// This macro reads the value of the following
// pins and packs the result into a single byte.
// RA0,RA1,RA4,RB2,RB5,RB7,RC0,RC5
#define read_spare_bits(x) \
x = 0; \
if(input(PIN_A0)) bit_set(x, 0); \
if(input(PIN_A1)) bit_set(x, 1); \
if(input(PIN_A4)) bit_set(x, 2); \
if(input(PIN_B2)) bit_set(x, 3); \
if(input(PIN_B5)) bit_set(x, 4); \
if(input(PIN_B7)) bit_set(x, 5); \
if(input(PIN_C0)) bit_set(x, 6); \
if(input(PIN_C5)) bit_set(x, 7);
//==================================
void main()
{
int8 result;
while(1)
{
// Read the value of the spare bits and put
// it into the 'result' variable.
read_spare_bits(result);
printf("Result = %X \n\r", result);
delay_ms(500);
}
} |
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Guest
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| Posted: Mon Jan 08, 2007 5:21 am |
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| I've just tried implementing the above macro set_spare_bits() and instead of turning on a static image on the 7-seg it cycles through the segments, one at a time, starting with one segment and then two, three, four, etc. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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