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Message |
redd501
Joined: 04 Nov 2003
Posts: 1
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| rs232 [and other] problems |
 Posted: Wed Jan 28, 2004 6:07 am |
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Hello all,
Ive got problems.
Im working on a little device that converts a (nearly) continuous input data stream through the rs232 port at 9600bps, and outputs a transformed version of the data at 500bps.
I am using the built in rs232 controller on the PIC to handle the incoming data, and i have written a function to output data on a particular pin in an rs232 format.
| Code: |
void soft232(int k)
{
int i;
int a[10];
a[0] = 0; // start bit
a[9] = 1; // stop bit
// fill packet with data
a[1] = k & 0b00000001;
a[2] = (k & 0b00000010) >> 1;
a[3] = (k & 0b00000100) >> 2;
a[4] = (k & 0b00001000) >> 3;
a[5] = (k & 0b00010000) >> 4;
a[6] = (k & 0b00100000) >> 5;
a[7] = (k & 0b01000000) >> 6;
a[8] = (k & 0b10000000) >> 7;
// output rs232 packet.
for(i=0;i<9;++i){
output_bit(soft232_Xmit, a[i]);
************************************************
delay_us(2000); // this delay sets the output pulse width.
************************************************
}
}
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The PIC I am using is a 16F877.
Now the problem i have is that you cannot transmit AND receive data at any one time. In its current state if I try to make my program work it accepts about 3 input characters and then crashes, which i assume would be the input rs232s' hardware buffer overflowing. If i reduce the delay
in the software232 then the program works just fine, so the delay must be holding up the processor in some way such that it is causing the input buffer to overflow.
So how on earth do i get around this????
BTW I dont have the luxuary of data streams as i have an old compiler.
_________________
there are only 10 types of people. those who understand binary and those who dont. |
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Jos
Joined: 15 Sep 2003
Posts: 4
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| Posted: Wed Jan 28, 2004 6:44 am |
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Try to use a software receive buffer. I use the example below. The isr will overwrite the last byte of rs232buffer[] if the sofware buffer is full. You should do the buffer reading in your "main" code! You will get hardware buffer overruns if your isr is to long.
#int_rda
void rda_isr(void)
{
byte tmpByte;
rs232buffer[nextByteIn] = getc();
tmpByte = nextByteIn;
nextByteIn = (nextByteIn + 1) % RS232_BUFFER_SIZE;
if(nextByteIn == nextByteOut)
{
nextByteIn = tmpByte; //Buffer full!
}
}
Greetz |
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Justy
Joined: 28 Jan 2004
Posts: 6
Location: Montréal
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| Posted: Wed Jan 28, 2004 1:45 pm |
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I'm programing right now throught rs232 and i've notice that you might be missing an instruction. I'm programing with Mplab system. So try this thing.
put on the top on your program
#use rs232 (baud=9600, xmit=pin_(pic pin out number), rcv=pin_(pic pin in number) ) |
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Justy
Joined: 28 Jan 2004
Posts: 6
Location: Montréal
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| Posted: Wed Jan 28, 2004 1:48 pm |
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sorry i've just notice that you are using the same pic as I do
so like i've said in your declaration ...not in your program right that
#include "16F877.h"
#use rs232 (baud=9600, xmit=pin_c6, rcv=pin_c7)
that should work |
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