How can I switch between two RS232 baud rates?

[jackie]

Hi, I am trying to collect serial data at 1200 baud and pass it out at 9600.

Switching between two different bauds (with #use rs232) does not work

Do i need two seperate RS232 controllers?
Do i have to use different pins?

What am i doing wrong?

Please HELP!

[Ttelmah]

[hillcraft]

This statement is not perfectly true.
//===========================
The #use RS232 system can be used, but requires very careful layout and programming to make it work. Basically, the 'last encountered' #use statement, must be the one you require.
//===========================
You can use streams to specify different speeds i.e.

#use rs232(baud=1200 ,parity=N,xmit=PIN_K_TX,rcv=PIN_K_RX,bits=8,ERRORS, stream=PORT_K_1200,RESTART_WDT)
#use rs232(baud=2400 ,parity=N,xmit=PIN_K_TX,rcv=PIN_K_RX,bits=8,ERRORS, stream=PORT_K_2400,RESTART_WDT)
#use rs232(baud=4800 ,parity=N,xmit=PIN_K_TX,rcv=PIN_K_RX,bits=8,ERRORS, stream=PORT_K_4800,RESTART_WDT)

You can then case on the desired speed i.e.

byte fgetcK2Speed_K() {
byte result;

switch (Protocol_Speed) {
case PS_1200:
result = fgetc(PORT_K_1200);
break;
case PS_2400:
result = fgetc(PORT_K_2400);
break;
case PS_4800:
result = fgetc(PORT_K_4800);
break;
case PS_9600:
result = fgetc(PORT_K_9600);
break;
}

return(result);
}

CCS will create appropriate code for ach stream

[rwyoung]

Will the stream trick work if the hardware UART is used? I would imagine it does work for the software UART code generated by the compiler.

Quick check of the July2003 manual says SET_UART_SPEED(baud,[stream]) is only good for the HARDWARE UART.
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!

[hillcraft]

You can use a hardware UART and a software UART. A software UART is just a bit of code that emulates a serial port. The CCS compiler generates the code automatically if it does not recognize the pins specified in your code to be the hardware UART pins.

The way I propose would be to use the hardware UART at 1200 BAUD. Then to use the receive interrupt to trigger the posting of the 9600 baud character.

// hardware uart
#use rs232(baud=19200,parity=N,xmit=PIN_C6,rcv=PIN_C7,bits=8,ERRORS,stream=PORT_PC,RESTART_WDT) // PC Comm speed

// software uart
#use rs232(baud=1200 ,parity=N,xmit=PIN_K_TX,rcv=PIN_K_RX,bits=8,ERRORS, stream=PORT_K_1200,RESTART_WDT)


PS. I don't know if the stream trick will work for the hardware UART but I suppose that I you specify the stream, then the compiler is obliged to generate the appropriate code. I think that the last #USE RS232 applies only to the default (unspecified) stream.

[jackie]

thanx guys!

[Ttelmah]

[treitmey]

Has anyone tried just setting up the standard stream, as a default, then on the 9600 transmit just change the spbrg/brgh value with #byte. TRANSMIT, then change the spbrg/brgh back for 1200? Or is this also too slow? This may be just what set_uart_speed does.

[karth]

set_uart_speed(115200);
delay_ms(10);
printf("baud rate set to 115200");
set_uart_speed(4800);
delay_ms(10);
printf("baud rate set to 4800");


good luck

[rwyoung]

[jackie]

OK, I got the speed to switch, but it will not allow change of parity!

which method should i be using to do this?

Thanx again!

[Neutone]

[Guest]

I would like to use streams as described in this topic. I'm curious if fputc() will block when writing to the software UART, and if not how much latency there might be. For example, if I want to echo bytes coming in on the hardware UART, can I just put fputc(c,SOFTUART) in the interrupt handler for the hardware UART receive?

[Guest]

Also... how does kbhit() know which UART to check? Right now, my code uses the hardware UART and recieve is done via #INT_RDA and a while ( kbhit() ) {inByte = getc();} kind of thing. The manual says kbhit() must be called 10x the bit rate for software UARTs. It's not clear to me how both of these would work when using both software and hardware UARTs.

[rwyoung]

Use the stream name as the argument in kbhit().
_________________
Rob Young
The Screw-Up Fairy may just visit you but he has crashed on my couch for the last month!