 |
 |
| View previous topic :: View next topic |
| Author |
Message |
bmete
Joined: 13 Jul 2023
Posts: 37
|
| PIC18F452 RS232 Receive Problem |
 Posted: Sat Aug 12, 2023 5:16 am |
 |
|
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);
}
}
|
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. |
|
 |
Ttelmah
Joined: 11 Mar 2010
Posts: 19540
|
|
| Posted: Sat Aug 12, 2023 5:35 am |
|
|
| Code: |
void main()
{
enable_interruptsGLOBAL);
while (1) {
|
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 |
|
|
temtronic
Joined: 01 Jul 2010
Posts: 9244
Location: Greensville,Ontario
|
|
| Posted: Sat Aug 12, 2023 5:35 am |
|
|
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 ??? |
|
|
Ttelmah
Joined: 11 Mar 2010
Posts: 19540
|
|
| Posted: Sat Aug 12, 2023 5:38 am |
|
|
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.... |
|
|
bmete
Joined: 13 Jul 2023
Posts: 37
|
|
| Posted: Sat Aug 12, 2023 6:12 am |
|
|
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);
|
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? |
|
|
Ttelmah
Joined: 11 Mar 2010
Posts: 19540
|
|
| Posted: Sat Aug 12, 2023 11:12 am |
|
|
Enable pin????.
What enable pin?.
Is this RS485, not RS232.
How is it wired?. |
|
|
bmete
Joined: 13 Jul 2023
Posts: 37
|
|
| Posted: Sat Aug 12, 2023 5:59 pm |
|
|
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);
}
}
}
}
|
|
|
|
Ttelmah
Joined: 11 Mar 2010
Posts: 19540
|
|
| Posted: Sun Aug 13, 2023 1:27 am |
|
|
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. |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
FAQ 
Search
Register
Profile 
Log in to check your private messages 
Log in
