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charles
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| RS485 Connection - #use rs232 |
 Posted: Thu May 11, 2006 6:42 pm |
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Hi,
I am quite a 4 days old beginner in microcontroller programming...
I am trying to setting up a RS485 connection between two PICs.
I have a first problem, it is that if I set the communication to be at a certain speed the sender receive the data 2 times slower, if I set the sender to send at twice as many baud it works fine (at leat for the early test, one receive the caracters the other send).
Then, if I try to define 2 stream to deal with the asymetry, one to send and one to receive :
| Code: | #use rs232(baud=SPEED_RX, xmit=RS485_TX_PIN, rcv=RS485_RX_PIN, enable=RS485_ENABLE_PIN, bits=9, /*long_data,*/ errors, stream=RS485RX)
#use rs232(baud=SPEED_TX, xmit=RS485_TX_PIN, rcv=RS485_RX_PIN, enable=RS485_ENABLE_PIN, bits=9, /*long_data,*/ errors, stream=RS485TX)
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apparently the second declaration overwrite the first one, I can use both stream but both have the settings of the second one.
Any help or documentation would be greatly appreciated,
Thanks,
Charles. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu May 11, 2006 7:53 pm |
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I assume you're using the hardware UART pins. If so, you can use
the setup_uart_speed() function to change the baudrate. Example:
| Code: |
#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#define SPEED_RX 4800
#define SPEED_TX 9600
#use rs232(baud=SPEED_RX, xmit=PIN_C6, rcv=PIN_C7, enable=PIN_C2, bits=9, /*long_data,*/ errors, stream=RS485RX)
#use rs232(baud=SPEED_TX, xmit=PIN_C6, rcv=PIN_C7, enable=PIN_C2, bits=9, /*long_data,*/ errors, stream=RS485TX)
//======================================
void main()
{
char c;
set_uart_speed(SPEED_TX, RS485TX);
fputc(0x55, RS485TX);
set_uart_speed(SPEED_RX, RS485RX);
c = fgetc(RS485RX);
while(1);
} |
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Guest
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| Posted: Fri May 12, 2006 5:14 pm |
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Hi, thanks for you help.
apparently the speed issue was due to the microcontrollers clock settings...
Thanks.
Charles. |
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