[En-Nut-Discussion] Problem on Using AT91SAM7X256 RS485 with Nut/OS

[Mingshu Wang]

Hi there,

I run into some problem when using RS485 on AT91SAM7X256 with Nut/OS. USART0 is connected to RS485 transceiver. I can transmit packets but I can't receive anything. 
I also made a version without Nut/OS which seems working fine.

The code that inializes the USART is as below. 
	FILE 			*rs485;
	unsigned long 	mstpbaudrate = 9600;
	
	//Register our devices.
	NutRegisterDevice(&DEV_UART, 0, 0);
    	rs485 = fopen(DEV_UART0_NAME, "rb+");//open in read/write binary mode    
    	outr(USART0_BASE + US_MR_OFF, AT91C_US_PAR_NONE | AT91C_US_CHMODE_NORMAL | AT91C_US_CHRL_8_BITS | AT91C_US_USMODE_RS485);                                        
    	_ioctl(_fileno(rs485), UART_SETSPEED, &mstpbaudrate);

Later I set the USART port into RS485 mode in the OS (function At91UsartInit() at \nut\arch\arm\dev\usartat91.c) instead of the application. I rebuild the OS but I still can NOT get the receiving work. Do I miss something?
    
/* Set UART mode to 8 data bits, no parity and 1 stop bit. */
outr(USARTn_BASE + US_MR_OFF, US_CHMODE_NORMAL | US_CHRL_8 | US_PAR_NO | US_NBSTOP_1 | 0x1);

Thanks for any help,

Mingshu