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Hans Wedemeyer
Joined: 15 Sep 2003
Posts: 226
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| How to change parity for RS232 hardware UART |
 Posted: Thu Mar 30, 2006 1:32 pm |
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SETUP_UART( ) allows Baud rate changes but how to change the parity.
As my code is using interrupts for RS232 reception the normal #use statement and ISR can't be duplicated.
I suspect the answer is to do it in assembly !
If anyone know a a CCS function to change Parity on the fly please let me know !
Thanks
hansw
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS)
#int_RDA
RDA_isr()
{
stuff received here will use parity=None
}
#use rs232(baud=9600,parity=O,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS)
#int_RDA
RDA_isr()
{
stuff received here will use parity=Odd
} |
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dmendesf
Joined: 31 Dec 2005
Posts: 32
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| Posted: Thu Mar 30, 2006 1:47 pm |
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I�ve tried this in the past, but it didn�t worked (or at least no with all compiler versions). Maybe you can try it again:
| Code: |
signed int set_mod_uart(unsigned long int baud, par_type parity, int stopbits)
{
disable_modbus();
g_parity = parity;
g_baud = baud;
switch(parity)
{
case O:
if(stopbits == 1)
{
#use rs232(baud=9600,parity=O,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
}
else return -1;
break;
case E:
if(stopbits == 1)
{
#use rs232(baud=9600,parity=E,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
}
else return -1;
break;
case N:
if(stopbits == 1)
{
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
}
else if(stopbits == 2)
{
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
TXSTA |= 0x41;
}
else return -1;
break;
}
switch(baud)
{
#if CCLOCK < 9497000
case 1200:
set_uart_speed(1200);
break;
#endif
case 2400:
set_uart_speed(2400);
break;
case 4800:
set_uart_speed(4800);
break;
case 9600:
set_uart_speed(9600);
break;
case 19200:
set_uart_speed(19200);
break;
case 38400:
set_uart_speed(38400);
break;
case 57600:
set_uart_speed(57600);
break;
case 115200:
set_uart_speed(115200);
break;
default:
return -1;
}
return 0;
} |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Mar 30, 2006 1:49 pm |
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I haven't tested this in hardware, but it looks like it should work.
You would set the "odd_parity_flag" at runtime, and then inside
the isr, the appropriate stream's code would be selected to receive
the character.
| Code: |
#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS, stream=No_Parity)
#use rs232(baud=9600,parity=O,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS, stream=Odd_Parity)
int8 odd_parity_flag = FALSE;
#int_RDA
RDA_isr()
{
char c;
if(odd_parity_flag == TRUE)
c = fgetc(Odd_Parity);
else
c = fgetc(No_Parity);
}
//============================
void main()
{
while(1);
} |
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Hans Wedemeyer
Joined: 15 Sep 2003
Posts: 226
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| possible solution |
| Posted: Thu Mar 30, 2006 1:51 pm |
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After reading the data sheet, Hardware uarts do not support parity. It has to be done in software.
I called CCS support and the suggestion is:
Use a second #use RS232 statement associated with a stream for the ODD parity, and then use fgetc() and fputc() for that stream. The compiler will figure out how to do the odd parity.
The ISR for the original #use RS232 will still get interrupted for each character received, however it's up to me to decide where in the code odd parity is needed.
If someone has a better suggestion please let me know...
Arrrrrrgh ! why does Trimble default to Odd parity ! |
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Hans Wedemeyer
Joined: 15 Sep 2003
Posts: 226
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| Thanks |
| Posted: Thu Mar 30, 2006 1:54 pm |
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PCM programmer:
Thanks it's similar to the CCS support suggestion, I'll give it a try...
hansw |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Mar 30, 2006 1:54 pm |
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| Well I answered that before CCS support did and I gave you sample code. |
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Hans Wedemeyer
Joined: 15 Sep 2003
Posts: 226
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| Not sure about this: |
| Posted: Thu Mar 30, 2006 1:56 pm |
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| dmendesf wrote: | I�ve tried this in the past, but it didn�t worked (or at least no with all compiler versions). Maybe you can try it again:
| Code: |
signed int set_mod_uart(unsigned long int baud, par_type parity, int stopbits)
{
disable_modbus();
g_parity = parity;
g_baud = baud;
switch(parity)
{
case O:
if(stopbits == 1)
{
#use rs232(baud=9600,parity=O,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
}
else return -1;
break;
case E:
if(stopbits == 1)
{
#use rs232(baud=9600,parity=E,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
}
else return -1;
break;
case N:
if(stopbits == 1)
{
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
}
else if(stopbits == 2)
{
#use rs232(baud=9600,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=MODBUS)
TXSTA |= 0x41;
}
else return -1;
break;
}
switch(baud)
{
#if CCLOCK < 9497000
case 1200:
set_uart_speed(1200);
break;
#endif
case 2400:
set_uart_speed(2400);
break;
case 4800:
set_uart_speed(4800);
break;
case 9600:
set_uart_speed(9600);
break;
case 19200:
set_uart_speed(19200);
break;
case 38400:
set_uart_speed(38400);
break;
case 57600:
set_uart_speed(57600);
break;
case 115200:
set_uart_speed(115200);
break;
default:
return -1;
}
return 0;
} |
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I think the #use RS232 statemnent is a compile time statement and can't be used at run time !
Thanks for the input.
hansw |
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dmendesf
Joined: 31 Dec 2005
Posts: 32
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| Posted: Thu Mar 30, 2006 2:30 pm |
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Well, i know that #defines are compile time statements but i�ve been told that in CCS the last #use defines what will your serial port do, so i�ve wrote this (stupid) code. I have a very good Modbus library (master and slave) but it can�t change stop bits / parity in real time beacuse of such oddities. Baudrate can be changed, no problems. I�ll try to recode this function using this idea of multiple streams... I�m just afraid of having to do this:
| Code: |
// Let�s transmit x to the serial port
switch(parity)
{
case N:
putc(x,NOPAR);
break;
case O:
putc(x,ODDPAR);
break;
case E:
putc(x,EVENPAR);
break;
}
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This would be silly. |
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Hans Wedemeyer
Joined: 15 Sep 2003
Posts: 226
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| Yes you did ! |
| Posted: Thu Mar 30, 2006 2:35 pm |
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| PCM programmer wrote: | | Well I answered that before CCS support did and I gave you sample code. |
Yes you did, and I appreciate the response, I'm sorry if you interpreted any other way.
Your replies are much respected, and valued my myself, and many other people.
I was just pointing out that is almost what CCS suggested !
Your reply came in while I was talking to CCS. |
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Hans Wedemeyer
Joined: 15 Sep 2003
Posts: 226
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| Posted: Thu Mar 30, 2006 2:38 pm |
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| dmendesf wrote: | Well, i know that #defines are compile time statements but i�ve been told that in CCS the last #use defines what will your serial port do, so i�ve wrote this (stupid) code. I have a very good Modbus library (master and slave) but it can�t change stop bits / parity in real time beacuse of such oddities. Baudrate can be changed, no problems. I�ll try to recode this function using this idea of multiple streams... I�m just afraid of having to do this:
| Code: |
// Let�s transmit x to the serial port
switch(parity)
{
case N:
putc(x,NOPAR);
break;
case O:
putc(x,ODDPAR);
break;
case E:
putc(x,EVENPAR);
break;
}
|
This would be silly. |
Thanks for the suggestion.
The issue is as you say it is.
The compiler will use the last #use statement which is a compile time statement.
Thanks. |
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