topic LPC1769 as RS485 slave device in LPC Microcontrollers

LPC1769 as RS485 slave device

kalpeshbalar — Sun, 26 Mar 2017 10:26:21 GMT

Hi, I am trying to use LPC1769 as RS485 slave device. And LPC11C14 used as master device.

Attached are master and slave program files.

If I enabble RECEIVER_ALWAYS_EN = 1 in slave then I am able to recive data on slave from the master.

But when I enable AUTO_SLVADDR_DETECT=1 in slave, I am not geting any data from master to slave.

What clould be wrong in attached master slave programs?

Thanks,

KBalar

Original Attachment has been moved to: master.c.zip

Original Attachment has been moved to: slave.c.zip

Re: LPC1769 as RS485 slave device

Carlos_Mendoza — Mon, 03 Apr 2017 21:20:24 GMT

Hi KBalar,

When in Auto Address Detection (AAD) mode the receiver will compare any address byte received (parity = ‘1’) to the 8-bit value programmed into the RS485ADRMATCH register so please make sure the UART master transmitter is correctly identifying the address character by setting the parity (9th) bit to ‘1’ and that the parity bit is set to ‘0’ for data characters.

Hope it helps!

Best Regards,
Carlos Mendoza
Technical Support Engineer

Re: LPC1769 as RS485 slave device

kalpeshbalar — Sat, 22 Apr 2017 07:28:32 GMT

Hi Carlos,

The master is already setting parity to 1 while sending the address. Please refer below code to send address from master. (Please refer attached code in main post.)

uint8_t tmp, save;
save = tmp = LPC_USART->LCR & UART_LCR_BITMASK;
tmp &= ~(UART_LCR_PARITY_EVEN);
LPC_USART->LCR = tmp;
if (addr_toggle){
Chip_UART_SendBlocking(LPC_USART, (void*)SLAVE_ADDR_A, 1);
} else {
Chip_UART_SendBlocking(LPC_USART, (void*)SLAVE_ADDR_B, 1);
}
while (!(LPC_USART->LSR & UART_LSR_TEMT));
LPC_USART->LCR = save;

What could be the problem?

Thanks,

KBalar