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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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Iīve tried this in the past, but it didnīt 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: | Iīve tried this in the past, but it didnīt 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 iīve been told that in CCS the last #use defines what will your serial port do, so iīve wrote this (stupid) code. I have a very good Modbus library (master and slave) but it canīt change stop bits / parity in real time beacuse of such oddities. Baudrate can be changed, no problems. Iīll try to recode this function using this idea of multiple streams... Iīm just afraid of having to do this:
| Code: |
// Letīs 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 iīve been told that in CCS the last #use defines what will your serial port do, so iīve wrote this (stupid) code. I have a very good Modbus library (master and slave) but it canīt change stop bits / parity in real time beacuse of such oddities. Baudrate can be changed, no problems. Iīll try to recode this function using this idea of multiple streams... Iīm just afraid of having to do this:
| Code: |
// Letīs 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. |
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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