RS485 problems

[DMH]

I'm having problems implementing the RS485.c code that's available with the complier. I'm using this code in conjunction with the ex_RS232_485.c that's also available with the complier.

I have 1 card configured as a master and another card configured as a slave, and the master card will transmit 1 character at a time over the RS485 bus. The slave card is receiving the character from the bus and then converted from 485 to 232 using a MAX1487 TXRX. The PIC18F6620 that I'm using receives the character from the MAX1487 as it should. I have 8 LEDs connected to Port E on the PIC, and I am trying to output the character on the LEDs with no success.

Can anyone help me with this?

The code I'm using is basically the same as the code in examples\ex_RS232_485.c

void main()
{
int8 i, msg[32];

enable_interrupts(INT_RDA);
enable_interrupts(INT_RDA2);
enable_interrupts(GLOBAL);
rs485_init();

for(;;)
{

if(rs485_get_message(msg, FALSE))
{
for(i=0; i<msg[1]; ++i)
{
fputc(msg[i+2], RS485_CD);
msg[i] = bgetc();
output_e(msg[3]);
}
for(i=0; bkbhit && i<sizeof(msg); ++i)
msg[i] = bgetc();

if(i > 0)
{
rs485_wait_for_bus(FALSE);
while(!rs485_send_message(RS485_DEST_ID, i, msg))
{
delay_ms(RS485_ID);
}
}
}
}

[Mark]

[DMH]

Mark

The code you suggested works perfectly!

I'm using Hyperterminal on my laptop which connnects to a 232-485 converter, which connects to RDA on the PIC. RDA2 connects to the MAX1487. When I measure RO on the MAX1487 with a scope and type 'U' in Hyperterminal, I see 1010101. I've also got an RS485 sniffer card connected across the bus from the master to slave cards, which is connected to a desktop PC running Hyperterminal. When the 'U' character is typed on my laptop, I see 5 characters displayed on the Desktop PC which represent source, destination, data-length, data, and checksum, as the 485.C code defines The 4th character displayed is 'U'.

Can you suggest any other way of displaying the character on port e?

The master card displays the incoming character from my laptop on port e perfectly.

Darren

[funmix]

Hi DMH,

Can you share your working code here? I wish to study the 485 communiction with PICs

Thanks!