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Setting up RS-232 with variables from program

 
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Dutch Guy



Joined: 20 Mar 2018
Posts: 21
Location: University of Antwerp

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Setting up RS-232 with variables from program
PostPosted: Mon Jun 28, 2021 2:22 pm     Reply with quote

PIC18F8722
CCSC 5.074

Greetings,

I need advice on how to setup a rs232 stream using variables from my program.
I have an initial

Code:
#use rs232(baud=MODBUS_SERIAL_BAUD, UART1, bits=8, stop=1, parity=E, stream=MODBUS_SERIAL, errors)


with the needed defines to work.

Now in my program I have a setup struct that can set and hold baudrates and parity by using a button menu.
Redefining baudrate with #use rs232(baud=x) is provided but HOW do I redefine parity with an int?
Nowhere I can find defines for N,E,U or the string like "EVEN". I tried numbers 0,1,2 and ASCII values for N,E,U

Is it even possible?

Where do I find the code generated by #use RS232 where the parity is implemented? Maybe I can shuffle in a extern variable?
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PCM programmer



Joined: 06 Sep 2003
Posts: 21477

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Re: Setting up RS-232 with variables from program
PostPosted: Mon Jun 28, 2021 5:41 pm     Reply with quote

Dutch Guy wrote:

Where do I find the code generated by #use RS232 where the parity is implemented?

Look under the #use rs232() statement in the .LST file. You will see
a loop that does XOR's.
temtronic



Joined: 01 Jul 2010
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PostPosted: Mon Jun 28, 2021 8:16 pm     Reply with quote

I would think a simple 'switch' function for 3 different 'use rs232(....)' should work ?
something like ...

switch (myparity) {
case(0):#use rs232(.....parity=none...);break;
case(1):#use rs232(....parity=odd...);break;
case(2):#use rs232(.....parity=even...);break;
}

...
where '0' means none,'1'=odd,'2'=even parity (easy for an dinosaur like me to remember...

Jay
Ttelmah



Joined: 11 Mar 2010
Posts: 17322

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PostPosted: Mon Jun 28, 2021 11:57 pm     Reply with quote

You cannot use variables for streams.
Key to understand is that a stream actually generates different compiled
code.
However you can (of course), use a variable to select which stream is
actually used.
So for parity:
Code:

#use rs232(baud=MODBUS_SERIAL_BAUD, UART1, bits=8, stop=1, parity=E, stream=MODBUS_EVEN, errors)
#use rs232(baud=MODBUS_SERIAL_BAUD, UART1, bits=8, stop=1, parity=O, stream=MODBUS_ODD, errors)
#use rs232(baud=MODBUS_SERIAL_BAUD, UART1, bits=8, stop=1, parity=N, stream=MODBUS_NONE, errors)

#define NONE 0
#define EVEN 2
#define ODD 1

byte Parity=NONE;

void my_putc(char chr)
{
    switch(Parity)
    {
        case NONE:
            putc(chr, MODBUS_NONE);
            break;
        case EVEN:
            putc(chr, MODBUS_EVEN);
            break;
        case ODD:
            putc(chr, MODBUS_ODD);
            break;
    }
}

char my_getc(void)
{
    switch(Parity)
    {
        case NONE:
            return getc(MODBUS_NONE));
            break;
        case EVEN:
            return getc(MODBUS_EVEN);
            break;
        case ODD:
            return getc(MODBUS_ODD);
            break;
    }
}


Then just use my_putc, and my_getc to put/get the characters, setting
the variable 'Parity' to the value required.

On baud rates, look at the example in the manual entry for
'set_uart_speed', which shows using two bits read from the input
port to change the baud rate.
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