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ljbeng
Joined: 10 Feb 2004
Posts: 205
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| Sending a Break Sequence |
 Posted: Wed Oct 05, 2011 8:45 am |
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I have a PIC16F1825 with hardware uart.
My Trimble GPS board will send me its hardware serial setup and other information such as model no. if I send it a 250ms min. duration break sequence. Once I do this, then the board will always respond at 9600 baud with the current setup information.
I want to do this at power up once. What is the best way to do this?
Here is a snippet of what I tried so far, but get no response. Should I force the TX pin low for 300ms at power up then setup the hardware uart to 9600? I will eventually use RDA interrupt but just want a working test for now.
| Code: |
output_high(pin_c4);
delay_ms(1000);
output_low(pin_c4);
delay_ms(300);
output_high(pin_c4);
#use rs232(baud=9600,parity=N,xmit=PIN_C4,rcv=PIN_C5,bits=8,stream=uar1,errors)
while (1){
if (kbhit(uar1)){
chr = fgetc(uar1);
buffer[pnt] = chr;
if (chr == 3) goto dn;//ETX (end of text)
if (pnt < 100) pnt++;
}
}
dn:
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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ljbeng
Joined: 10 Feb 2004
Posts: 205
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| Posted: Fri Oct 07, 2011 8:33 am |
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Thanks, I looked at that thread.
It must be because the chip is a 16F1825 but I am getting a Undefined Identifier when I try to use setup_uart(false) with V4.124 |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19253
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| Posted: Fri Oct 07, 2011 9:23 am |
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Reason for that, is that the compiler doesn't know you want to use the hardware UART. You need to use:
| Code: |
#use rs232(baud=0,parity=N,UART1,bits=8,stream=PORT1)
//Note baud=0, and selected UART1, not pins
void main() {
setup_comparator(NC_NC_NC_NC);
output_low(PIN_C4);
delay_ms(100); //100mSec break
output_high(PIN_C4);
setup_uart(9600); //Enable UART
fprintf(PORT1,"Test message \n\r");
setup_uart(FALSE);
output_low(PIN_C4);
delay_ms(100); //100mSec break
output_high(PIN_C4);
setup_uart(9600); //Enable UART
fprintf(PORT1,"Test message #2 \n\r");
do {
} while(TRUE);
}
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Using 'BAUD=0', leaves the UART unconfigured on boot, and it is turned on, when you set a baud rate. Using 'UART1', tells the compiler to use the hardware UART, not implement a software UART. Though C4, and C5, are the default pins for RX/TX, the compiler doesn't 'know' that the UART is on these pins, so implements a software UART.....
This should send two breaks, with the two test messages.
Best Wishes |
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