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sindyvirgo
Joined: 15 Jan 2009
Posts: 8
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| How can I use software RS232 get data |
 Posted: Thu Feb 12, 2009 3:12 am |
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I want to use more RS232 to Receive & Conveyance.
I have consulted the example of CCS.
| Code: | #USE RS232(BAUD=4800, XMIT=PIN_B0, RCV=PIN_B1, STREAM=COM_A) //software Port1
#USE RS232(BAUD=4800, XMIT=PIN_B2, RCV=PIN_B3, STREAM=COM_B) //software Port2 & a Hardware RS232 C6 C7 Pin
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Total : *3 RS232 (one Hardware two Software)
Now ~
My Software RS232 can only convey and can't receive.
| Code: | #int_RDA
void RDA_isr()
{
Com1_buf = getc();
printf("%c",Com1_buf);
}
while(TRUE) {
Com3_buf = fgetc(COM_A);
fprintf(COM_A,"%c",Com3_buf);
} |
Software Rs232 NO work ; Hardware 232 can use
Could you tell me how to do ? |
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karthickiw
Joined: 09 Aug 2007
Posts: 82
Location: TN, India
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| software RS232 |
| Posted: Sun Feb 22, 2009 7:59 am |
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hi,
#int_RDA is not working in software UART... |
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Ttelmah
Guest
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| Posted: Sun Feb 22, 2009 10:25 am |
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You don't say 'what PIC'.
It is possible to use a software UART, in a 'semi interrupt' mode, by connecting the incoming serial line to a pin that has a hardware interrupt, and receiving when this triggers.
So, assuming your PIC, has the INT line on B0, if you swapped the xmit/receive definitions on your first serial, then programmed B0 to interrupt on a falling edge, you could perform a software receive in the INT_EXT interrupt handler.
_But_ you have to remember that software serials, are very restrictive. If a receive occurs, while you are transmitting on another software serial, _this transmission will be garbage_. The CCS code, can only ever handle, one software reception, _or_ one software transmission at any time. Also, the software serial, _must_ start to sample incoming data, within one half a bit time of the first falling edge. It takes typically 30+ instructions minimum to actually get 'into' an interrupt handler, and if the PIC was (for example), inside another interrupt handler, at the moment the edge arrived, this could easily increase to 100+ instructions. So the ability to do this, is _very_ dependant on your clock rate, relative to the baud rate.
A search here, will find code examples for using the software serial 'interrupt driven'.
Best Wishes |
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