uart speed problem

[mulab]

I'm using UART at 250KBaud for DMX512 application.

The transmit is done changing Uart Speed but the first
change has no effect, the output is always at 250Kb.


#include <18C452.h)

#use rs232(baud=250000, parity=N, xmit=PIN_C6, rcv=PIN_C7, bits=9, BRGH1OK)


main
{
....
set_uart_speed(96150);
putc(0); ////this is done at 250Kb!!!
////the assembler done correctly

set_uart_speed(250000);
for(i=0; i<512; i++)
{
putc(channel[i]);

}

}
___________________________
This message was ported from CCS's old forum
Original Post ID: 4073

[Mark]

I did an application a while back using a 16F876 as a DMX receiver to I2C transmiter to interface our product line to DMX. For testing the performance of the product I wrote some code to generate a DMX stream. I believe that you are trying to generate the break signal or "Mark" (I think that is the proper term). The following is some of the code that I used. I usually try not to use the CCS functions but I think you should be able to see how I accomplished this. CCS changed their compiler so if you use the notation *REG you will have to cast it like (int)*REG = Somevalue. If you have any questions please ask.

Mark

void main(void)
{
UINT8 index = 0; /* index */

/* initialize variables first, since initializing pic
will allow interrupts to begin occurring */
Initialize_Variables();

Init_PIC();

/* read the shift registers */
Read_Inputs();


/* set levels */
memset(levels,0,sizeof(levels));

/* Start sending the DMX stream */
Send_Break = TRUE;
Send_Start_Code = FALSE;

/* This is the main loop code */
while (TRUE)
{
restart_wdt();

/************************************************************************
* Dynamic Options *
************************************************************************/

if (Send_Break && bit_test(*TXSTA, 1))
{
DATA_LED_ON();
RS485_TRANSMIT_ENABLE();
/* serial port disable */
bit_clear(*RCSTA,SPEN);
setup_timer_1(T1_DISABLED);
bit_clear(*PIR1, TMR1IF);
bit_clear(*PIE1, TXIE);
/* Setup Timer1 for 88us break signal
Timer1 increments every .2us the 47 is the interrupt lag */
set_timer1(0xFFFF-(440 - 47));
bit_clear(*PORTC, 0x06);
setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
bit_set(*PIE1, TMR1IE);
Send_Break = FALSE;
}

else if (Send_Start_Code)
{
Send_Start_Code = FALSE;
delay_us(3);

/* Send start code */
*TXREG = 0;

/* serial port enable */
bit_set(*RCSTA,SPEN);

/* Start transmission */
bit_set(*TXSTA,TXEN);
bit_set(*TXSTA,6);
bit_set(*TXSTA,0);
bit_set(*PIE1, TXIE);
}

/* See if it is time to read the switch inputs */
else if (!Switch_Timeout)
{
Read_Inputs();
/* Read the switch inputs every 2 secs */
Switch_Timeout = 20;
}
else if (!JUMPER_LK2_BOTTOM_OFF())
{
memset(levels,255,sizeof(levels));
}
else if (!JUMPER_LK2_TOP_OFF())
{
memset(levels,0,sizeof(levels));
}
else if (!Delay_Timeout && (Max_Dimmers > 0))
{
switch (Shift_Reg_Inputs.data.i2c)
{
case 0:
memset(levels,0,sizeof(levels));
levels[index] = 255;
++index;
if (index >= Max_Dimmers)
index = 0;
break;
case 1:
memset(levels,0,sizeof(levels));
levels[index] = 255;
if (!index)
index = Max_Dimmers;
--index;
break;
case 2:
if (index >= Max_Dimmers)
{
memset(levels,0,sizeof(levels));
index = 0;
}
else
{
levels[index] = 255;
++index;
}
break;
default:
memset(levels,0,sizeof(levels));
levels[index] = 255;
++index;
if (index >= Max_Dimmers)
index = 0;
break;
}
Delay_Timeout = Delay_Time;
}

} /* end of forever loop */

}



/****************************************************************************
* NAME: Tx_Data
* DESCRIPTION: Transmits a byte using the UART to a DMX universe
* PARAMETERS: none
* GLOBALS: UINT8 Tx_Index (IO) transmit buffer pointer
* UINT8 Tx_Buffer (IO) transmit buffer
* RETURN: none
* ALGORITHM: none
* NOTES: none
*****************************************************************************/
#INT_TBE
void Tx_Data(void)
{
static UINT8 tx_index = 0;

while (bit_test(*INTCON,0x07))
bit_clear(*INTCON,0x07);

DATA_LED_OFF();
if (!Max_Dimmers)
{
bit_clear(*PIE1, TXIE);
tx_index = 0;
Send_Break = TRUE;

}
else
{
*TXREG = levels[tx_index];
bit_set(*TXSTA,TXEN);
/* Transmit nine data bits, one is used for the stop bit */
bit_set(*TXSTA,6);
bit_set(*TXSTA,0);
++tx_index;
if (tx_index >= Max_Dimmers)
{
/* Disable the interrupt if we are done transmitting */
bit_clear(*PIE1, TXIE);
tx_index = 0;
Send_Break = TRUE;
}
}
}

/****************************************************************************
* NAME: Timer1_ISR
* DESCRIPTION:
* PARAMETERS: none
* GLOBALS: none
* RETURN: none
* ALGORITHM: none
* NOTES: none
*****************************************************************************/
#INT_TIMER1
void Timer1_ISR(void)
{
while (bit_test(*INTCON, 0x07)) /* make sure interrupts were */
bit_clear(*INTCON, 0x07); /* disabled. */

/* Disable Timer1 int */
setup_timer_1(T1_DISABLED);

bit_set(*PORTC, 0x06);
Send_Start_Code = TRUE;

}

:=I'm using UART at 250KBaud for DMX512 application.
:=
:=The transmit is done changing Uart Speed but the first
:=change has no effect, the output is always at 250Kb.
:=
:=
:=#include <18C452.h)
:=
:=#use rs232(baud=250000, parity=N, xmit=PIN_C6, rcv=PIN_C7, bits=9, BRGH1OK)
:=
:=
:=main
:={
:= ....
:= set_uart_speed(96150);
:= putc(0); ////this is done at 250Kb!!!
:= ////the assembler done correctly
:=
:= set_uart_speed(250000);
:= for(i=0; i<512; i++)
:= {
:= putc(channel[i]);
:=
:= }
:=
:=}
___________________________
This message was ported from CCS's old forum
Original Post ID: 4077

[mulab]

Thank you fo reply,

Really I'm tryng to C solution to replace my old assembler
based code.
While waiting for a message reply I have found this solution:

set_uart_speed(96150);
putc(0); //this is done at 96.15Kb!!!
putc(0); //I thing this byte and following
//flushes tx buffer
putc(0); //this is done at 250Kb, but is ok
//(dmx stream start code)

set_uart_speed(250000);
for(i=0; i<512; i++)
{
putc(channel[i]);
}

This generate a dmx stream with break time over 88 us and
mab time over 8 us.
I'm not understand if this is done ok due to hardware serial
buffer flushing.

:=I did an application a while back using a 16F876 as a DMX receiver to I2C transmiter to interface our product line to DMX. For testing the performance of the product I wrote some code to generate a DMX stream. I believe that you are trying to generate the break signal or "Mark" (I think that is the proper term). The following is some of the code that I used. I usually try not to use the CCS functions but I think you should be able to see how I accomplished this. CCS changed their compiler so if you use the notation *REG you will have to cast it like (int)*REG = Somevalue. If you have any questions please ask.
:=
:=Mark
:=
:=void main(void)
:={
:= UINT8 index = 0; /* index */
:=
:= /* initialize variables first, since initializing pic
:= will allow interrupts to begin occurring */
:= Initialize_Variables();
:=
:= Init_PIC();
:=
:= /* read the shift registers */
:= Read_Inputs();
:=
:=
:= /* set levels */
:= memset(levels,0,sizeof(levels));
:=
:= /* Start sending the DMX stream */
:= Send_Break = TRUE;
:= Send_Start_Code = FALSE;
:=
:= /* This is the main loop code */
:= while (TRUE)
:= {
:= restart_wdt();
:=
:= /************************************************************************
:= * Dynamic Options *
:= ************************************************************************/
:=
:= if (Send_Break && bit_test(*TXSTA, 1))
:= {
:= DATA_LED_ON();
:= RS485_TRANSMIT_ENABLE();
:= /* serial port disable */
:= bit_clear(*RCSTA,SPEN);
:= setup_timer_1(T1_DISABLED);
:= bit_clear(*PIR1, TMR1IF);
:= bit_clear(*PIE1, TXIE);
:= /* Setup Timer1 for 88us break signal
:= Timer1 increments every .2us the 47 is the interrupt lag */
:= set_timer1(0xFFFF-(440 - 47));
:= bit_clear(*PORTC, 0x06);
:= setup_timer_1(T1_INTERNAL|T1_DIV_BY_1);
:= bit_set(*PIE1, TMR1IE);
:= Send_Break = FALSE;
:= }
:=
:= else if (Send_Start_Code)
:= {
:= Send_Start_Code = FALSE;
:= delay_us(3);
:=
:= /* Send start code */
:= *TXREG = 0;
:=
:= /* serial port enable */
:= bit_set(*RCSTA,SPEN);
:=
:= /* Start transmission */
:= bit_set(*TXSTA,TXEN);
:= bit_set(*TXSTA,6);
:= bit_set(*TXSTA,0);
:= bit_set(*PIE1, TXIE);
:= }
:=
:= /* See if it is time to read the switch inputs */
:= else if (!Switch_Timeout)
:= {
:= Read_Inputs();
:= /* Read the switch inputs every 2 secs */
:= Switch_Timeout = 20;
:= }
:= else if (!JUMPER_LK2_BOTTOM_OFF())
:= {
:= memset(levels,255,sizeof(levels));
:= }
:= else if (!JUMPER_LK2_TOP_OFF())
:= {
:= memset(levels,0,sizeof(levels));
:= }
:= else if (!Delay_Timeout && (Max_Dimmers > 0))
:= {
:= switch (Shift_Reg_Inputs.data.i2c)
:= {
:= case 0:
:= memset(levels,0,sizeof(levels));
:= levels[index] = 255;
:= ++index;
:= if (index >= Max_Dimmers)
:= index = 0;
:= break;
:= case 1:
:= memset(levels,0,sizeof(levels));
:= levels[index] = 255;
:= if (!index)
:= index = Max_Dimmers;
:= --index;
:= break;
:= case 2:
:= if (index >= Max_Dimmers)
:= {
:= memset(levels,0,sizeof(levels));
:= index = 0;
:= }
:= else
:= {
:= levels[index] = 255;
:= ++index;
:= }
:= break;
:= default:
:= memset(levels,0,sizeof(levels));
:= levels[index] = 255;
:= ++index;
:= if (index >= Max_Dimmers)
:= index = 0;
:= break;
:= }
:= Delay_Timeout = Delay_Time;
:= }
:=
:= } /* end of forever loop */
:=
:=}
:=
:=
:=
:=/****************************************************************************
:=* NAME: Tx_Data
:=* DESCRIPTION: Transmits a byte using the UART to a DMX universe
:=* PARAMETERS: none
:=* GLOBALS: UINT8 Tx_Index (IO) transmit buffer pointer
:=* UINT8 Tx_Buffer (IO) transmit buffer
:=* RETURN: none
:=* ALGORITHM: none
:=* NOTES: none
:=*****************************************************************************/
:=#INT_TBE
:=void Tx_Data(void)
:={
:= static UINT8 tx_index = 0;
:=
:= while (bit_test(*INTCON,0x07))
:= bit_clear(*INTCON,0x07);
:=
:= DATA_LED_OFF();
:= if (!Max_Dimmers)
:= {
:= bit_clear(*PIE1, TXIE);
:= tx_index = 0;
:= Send_Break = TRUE;
:=
:= }
:= else
:= {
:= *TXREG = levels[tx_index];
:= bit_set(*TXSTA,TXEN);
:= /* Transmit nine data bits, one is used for the stop bit */
:= bit_set(*TXSTA,6);
:= bit_set(*TXSTA,0);
:= ++tx_index;
:= if (tx_index >= Max_Dimmers)
:= {
:= /* Disable the interrupt if we are done transmitting */
:= bit_clear(*PIE1, TXIE);
:= tx_index = 0;
:= Send_Break = TRUE;
:= }
:= }
:=}
:=
:=/****************************************************************************
:=* NAME: Timer1_ISR
:=* DESCRIPTION:
:=* PARAMETERS: none
:=* GLOBALS: none
:=* RETURN: none
:=* ALGORITHM: none
:=* NOTES: none
:=*****************************************************************************/
:=#INT_TIMER1
:=void Timer1_ISR(void)
:={
:= while (bit_test(*INTCON, 0x07)) /* make sure interrupts were */
:= bit_clear(*INTCON, 0x07); /* disabled. */
:=
:= /* Disable Timer1 int */
:= setup_timer_1(T1_DISABLED);
:=
:= bit_set(*PORTC, 0x06);
:= Send_Start_Code = TRUE;
:=
:=}
:=
:=:=I'm using UART at 250KBaud for DMX512 application.
:=:=
:=:=The transmit is done changing Uart Speed but the first
:=:=change has no effect, the output is always at 250Kb.
:=:=
:=:=
:=:=#include <18C452.h)
:=:=
:=:=#use rs232(baud=250000, parity=N, xmit=PIN_C6, rcv=PIN_C7, bits=9, BRGH1OK)
:=:=
:=:=
:=:=main
:=:={
:=:= ....
:=:= set_uart_speed(96150);
:=:= putc(0); ////this is done at 250Kb!!!
:=:= ////the assembler done correctly
:=:=
:=:= set_uart_speed(250000);
:=:= for(i=0; i<512; i++)
:=:= {
:=:= putc(channel[i]);
:=:=
:=:= }
:=:=
:=:=}
___________________________
This message was ported from CCS's old forum
Original Post ID: 4107