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treitmey
Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA
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| questtion on a software RS232 and unused pin |
 Posted: Tue Jan 04, 2005 5:39 pm |
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Using a 16F877 @ 16 MhZ and CCS 3.214
Why would adding an unused pin to this program make it work.
| Code: | #use rs232(baud=9600,xmit=PIN_A2,errors,invert,stream=DEBUG)
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when changed to this
| Code: | #use rs232(baud=9600,xmit=PIN_A2,rcv=PIN_A3,errors,invert,stream=DEBUG)
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makes it work, ... but I don't use the rcv pin??
stream U13 is rcv serial data from another PIC (B0 tied to B0) without a pull up or anything.
| Code: |
#include <16f877.h>
#device *=16
#case
#use delay(clock=16000000,RESTART_WDT)
#fuses hs,nowdt,noprotect,nolvp
#define VER_MAJOR 1
#define VER_MINOR 00
#use rs232(baud=9600,xmit=PIN_A2,rcv=PIN_A3,errors,invert,stream=DEBUG)
#use rs232(baud=9600,rcv=PIN_B0,errors,stream=U13)
#zero_ram
char getaddress(void);
void main(void)
{
int8 myaddr;
setup_adc_ports(NO_ANALOGS);
disable_interrupts(GLOBAL);
set_tris_a(0xFF);
set_tris_b(0xFF);
set_tris_c(0xFF);
set_tris_d(0xFF);
set_tris_e(0xFF);
//--------- START -------//
fprintf(DEBUG,"STARTING U11\n\r");
fprintf(DEBUG,"FIRMWARE VERSION %u.%02u\n\r",VER_MAJOR,VER_MINOR);
myaddr=getaddress();
fprintf(DEBUG,"MyAddr=%U or 0x%X\r\n",myaddr,myaddr);
while(TRUE)
{
;
}
}
char getaddress(void)
{
int8 addr[4];
do
{
if (kbhit()) addr[0]=fgetc(U13);//new value read into 0
if (kbhit()) addr[1]=fgetc(U13);//new value read into 1
if (kbhit()) addr[2]=fgetc(U13);//new value read into 2
if (kbhit()) addr[3]=fgetc(U13);//new value read into 3
fprintf(DEBUG,"%U %U %U %U\r\n",addr[0],addr[1],addr[2],addr[3]);
}while(addr[0]!=addr[1] ||
addr[0]!=addr[2] ||
addr[0]!=addr[3]);//look for 4 addr that are the same
return(addr[0]);
} |
with the extra RCV pin define my code works and a 0x131 is seen on stream U13. Without it I get a 17. ???/
The change is just in my debug code.
And somehow changes the data I see on stream U13.
This just doesn't make sense. |
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treitmey
Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA
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| Posted: Tue Jan 04, 2005 5:59 pm |
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--
Last edited by treitmey on Wed Jan 05, 2005 9:32 am; edited 1 time in total |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Wed Jan 05, 2005 2:31 am |
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Your change making the code work is just coincidence, both versions are wrong.
Error 1: You are calling kbhit() without specifying which stream to use. From the manual: | Quote: | | If the stream parameter is not included, the function uses the primary stream used by getc(). |
In your first version no I/O-pin is defined for your primary stream, resulting in undefined behaviour. The second version has the rx-pin defined, but for the wrong stream. Both versions shouldn't work....
Error 2: The kbhit() function is non-blocking, addr[0], 1, 2 and 3 are not synchronized and will (potentially) read garbage data.
Solution: Remove all kbhit() calls.
| Code: | char getaddress(void)
{
int8 addr[4];
do
{
addr[0]=fgetc(U13);//new value read into 0
addr[1]=fgetc(U13);//new value read into 1
addr[2]=fgetc(U13);//new value read into 2
addr[3]=fgetc(U13);//new value read into 3
fprintf(DEBUG,"%U %U %U %U\r\n",addr[0],addr[1],addr[2],addr[3]);
}while(addr[0]!=addr[1] ||
addr[0]!=addr[2] ||
addr[0]!=addr[3]);//look for 4 addr that are the same
return(addr[0]);
} |
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treitmey
Joined: 23 Jan 2004
Posts: 1094
Location: Appleton,WI USA
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| Posted: Wed Jan 05, 2005 8:41 am |
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Thanks for finding the error.
I don't use kbhit often. Should have know that would be the problem.
That was pretty obvious, I just needed to get away from the problem for a while. |
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