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AkinKonak
Joined: 04 Oct 2012
Posts: 1
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| Serial Communication |
 Posted: Thu Oct 04, 2012 3:09 am |
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Hello Guys,
We are trying to setup a serial communication via other ports which are not RX/TX (hardware communication ports) and we are facing with the problem that the program is waiting until the serial data arrives. This means that if the data never arrives then the program gets stuck there.
We want the program to return back to the loop if the serial data does not arrive within 5 ms (eg.)
Can you please let us know how we can achieve this and provide us the sample code ?
Thanks in advance for your time and assistance.
Best Regards,
Akin |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19399
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| Posted: Thu Oct 04, 2012 4:29 am |
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Roughly:
| Code: |
int16 wait_for;
waitfor=1000;
do {
if (kbhit()) {
//here get your data and exit
break;
}
delay_us(5);
} while (--waitfor>0);
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kbhit, returns immediately, but tells you if the incoming serial line has dropped (signalling the start of a character). So this will loop 1000*, testing kbhit, and waiting 5uSec between tests -> so slightly over 5mSec, and getting the data if it arrives.
Best Wishes |
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John P
Joined: 17 Sep 2003
Posts: 331
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| Posted: Thu Oct 04, 2012 12:47 pm |
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You shouldn't "wait until serial data arrives". But if you have a processor with a single UART, using other pins for software UARTs is quite challenging. You might do better to buy a few cheap PICs and use them just for the UART function, and get them to talk to your processor via some other interface.
If you just want one extra UART, and if it doesn't have to be full duplex, you can do it easily enough using an interrupt, first on a low-going edge (the start bit) and then again with a timer, once on each data bit. That way the processor never has to "wait" for communication at all. |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Thu Oct 04, 2012 4:15 pm |
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if your problem is requiring more than 1 RS-232 i/o pair then have you considered parts like the very cost effective 18F4xK22 and the 18F2xk22
with DUAL hardware serial ports ???
( and a raft of other useful hardware functions , downright CHEAP tool) |
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bkamen
Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA
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| Posted: Thu Oct 04, 2012 6:54 pm |
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| asmboy wrote: | if your problem is requiring more than 1 RS-232 i/o pair then have you considered parts like the very cost effective 18F4xK22 and the 18F2xk22
with DUAL hardware serial ports ???
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Agreed -- for all the hassles of dealing with 2 serial ports, get a PIC with > 1 hardware EUSARTs.
All the hassle goes away.
-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D |
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John P
Joined: 17 Sep 2003
Posts: 331
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| Posted: Fri Oct 05, 2012 9:41 am |
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| OK, but what if the requirement is 3 or 4 or more UARTs? The guy never said how many he wants, and everyone is talking as if 1 extra will do the job. |
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asmboy
Joined: 20 Nov 2007
Posts: 2128
Location: albany ny
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| Posted: Fri Oct 05, 2012 10:12 am |
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| Quote: |
3 or 4 or more UARTs?
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external 16* family 4 or 8 uarts with FIFO awkward but can work
hardware is the only way to go .......
IMHO ONE or more software USARTS is at least ONE too many.
it is a wholly unreliable way to code a commercial work - 4 sure, since
sooner or later the RX function will return junk bytes , and
software Rs232 transmit will fail if there are interrupts are enabled. |
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bkamen
Joined: 07 Jan 2004
Posts: 1611
Location: Central Illinois, USA
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| Posted: Fri Oct 05, 2012 11:39 am |
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| John P wrote: | | OK, but what if the requirement is 3 or 4 or more UARTs? The guy never said how many he wants, and everyone is talking as if 1 extra will do the job. |
If the poster wants more than 2, then look to the PIC24 and PIC32 series of microcontrollers *IF HE wants them built in*.
I did a PIC project with an external Octal UART connected to a pic18F97J60 and that worked as well - with known limitations.
-Ben
_________________
Dazed and confused? I don't think so. Just "plain lost" will do. :D |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19399
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| Posted: Fri Oct 05, 2012 1:27 pm |
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Or of course quite a few I2C UART's, or just a second PIC.
Best Wishes |
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