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bmete
Joined: 13 Jul 2023
Posts: 33
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| PIC18F452 RS232 Receive Problem |
 Posted: Sat Aug 12, 2023 5:16 am |
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Hello everyone.
I am trying to provide RS232 communication with Pic18f452 chip. With the code I shared below, I can send data to the serial port via Putty, but unfortunately, when I try to receive data from the putty terminal to the PIC, the code stops for some reason. | Code: |
#use delay(clock=20000000)
#fuses HS, NOWDT, PUT, BROWNOUT, NOLVP
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, parity=N, stop=1, bits=8, RECEIVE_BUFFER=128, ERRORS/*, TXISR*/)
void main()
{
while (1) {
printf("Enter: \n");
putc(54);
output_low(PIN_D4);
delay_ms(5);
c = getc();
if (c == 'a')
{
output_high(PIN_C2);
delay_ms(5);
printf(" yes ");
}
else
printf(" no ");
delay_ms(1000);
}
}
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In the code above, no matter what value I send from the terminal, the code stops, so it's like it can't call the getc function.
I used to communicate with the PIC18f2520 with a very similar configuration and without any problems, but for some reason I cannot receive data with this chip.
I would be very grateful if you could help me with this. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19231
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| Posted: Sat Aug 12, 2023 5:35 am |
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| Code: |
void main()
{
enable_interruptsGLOBAL);
while (1) {
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Note the single extra line.
You are not enabling the global interrupt, so with the receive buffer, the
receive cannot work.
Last edited by Ttelmah on Sat Aug 12, 2023 5:35 am; edited 1 time in total |
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temtronic
Joined: 01 Jul 2010
Posts: 9117
Location: Greensville,Ontario
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| Posted: Sat Aug 12, 2023 5:35 am |
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I don't like the ...ERRORS/*...... )
Maybe the compiler can properly decode and not complain BUT just delete instead,compile and test run. see if that helps ??? |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19231
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| Posted: Sat Aug 12, 2023 5:38 am |
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He isn't enabling the TX buffer, so TXISR doesn't do anything.
He is though enabling the receive interrupt, but not enabling the global
interrupt, so it won't work.... |
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bmete
Joined: 13 Jul 2023
Posts: 33
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| Posted: Sat Aug 12, 2023 6:12 am |
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Hello Ttelmah, temtronic. Thanks for quick replies.
| Code: |
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, parity=N, stop=1, bits=8, RECEIVE_BUFFER=128, ERRORS)
enable_interrupts(GLOBAL);
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I enabled global interrupts and edited fuses as you said. However, I still cannot use the getc function in the same way.
Previously, when working with the 18F2520, I had to switch the enable pin before each transmit or receive operation. So I did the same, thinking that this will be the case with this chip as well. Could there be a problem with it? |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19231
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| Posted: Sat Aug 12, 2023 11:12 am |
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Enable pin????.
What enable pin?.
Is this RS485, not RS232.
How is it wired?. |
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bmete
Joined: 13 Jul 2023
Posts: 33
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| Posted: Sat Aug 12, 2023 5:59 pm |
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Yes this is RS485 I am using SN75176.
As far as I know, when I configure RS232 to the PIC and use it with an IC like SN75176, I create a proper RS485 communication. Please correct me if I'm wrong.
It looks like I'm currently communicating properly with the following settings.
| Code: |
#use delay(crystal=20MHz)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, parity=N, stop=1, bits=8, RECEIVE_BUFFER=128, ERRORS, TXISR)
#define USE_TX_ISR
#define RS232ENABLE PIN_D4
void main()
{
enable_interrupts(GLOBAL);
while(TRUE)
{
output_low(RS232ENABLE);
delay_ms(5);
if (kbhit()) {
c = getc();
if (c == '1')
{
output_high(OUT1);
printf("\r\n#OUT1 ");
delay_ms(5);
}
}
}
}
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Ttelmah
Joined: 11 Mar 2010
Posts: 19231
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| Posted: Sun Aug 13, 2023 1:27 am |
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No, you don't......
You have to tell the #USE RS232 to operate the direction control pin.
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, parity=N, stop=1, bits=8, RECEIVE_BUFFER=32, ERRORS, ENABLE=PIN_D4)
I'm assuming what you are calling 'enable' is actually the direction
control line.
You only need to enable TXISR, if you enable a transmit buffer. Seriously,
128, is a huge receive buffer. I have turned this down. If you want to
use interrupt driven transmit, then setup a transmit buffer, and enable
this. |
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