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News: Glomation introduced new wireless ready low cost GESBC-9260S

[gurtlerc]

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Hi,

Does anyone have some sample code for using the RS485 port?

[slonko]

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Hi,

Does anyone have some sample code for using the RS485 port?

Hi gurtlerc,
Do you mean the one on the J16 I/O Expansion?
I have just noticed it too and it would be useful if I can use it on my board that doesn't have any RS485 driver chip on, will do some research..

[admin]

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The RS-485 on GESBC-9260 is connected to USART3 of the AT91SAM9260 processor.  The 9260 processor has a hardware RS-485 mode.  It can be set by one of the serial port control registers.  Once it is set to RS-485 mode, the serial port can be used directly like any other Linux serial devices.

The kernel should have USART3 enabled with RTS pin included,

/arch/arm/mach-at91/board-sam9260ek.c

static void __init ek_map_io(void)

        /* USART3 on ttyS4. (Rx, Tx, RTS) */
        at91_register_uart(AT91SAM9260_ID_US3, 4, ATMEL_UART_RTS);


The USART mode register can be set with the devmem2 utility in user space,

devmem2 0xfffd0004 w 0xc00008c1


The Linux standard serial device control can be used to set baudrate etc.

[slonko]

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The RS-485 on GESBC-9260 is connected to USART3 of the AT91SAM9260 processor.  The 9260 processor has a hardware RS-485 mode.  It can be set by one of the serial port control registers.  Once it is set to RS-485 mode, the serial port can be used directly like any other Linux serial devices.

The kernel should have USART3 enabled with RTS pin included,

/arch/arm/mach-at91/board-sam9260ek.c

static void __init ek_map_io(void)

        /* USART3 on ttyS4. (Rx, Tx, RTS) */
        at91_register_uart(AT91SAM9260_ID_US3, 4, ATMEL_UART_RTS);


The USART mode register can be set with the devmem2 utility in user space,

devmem2 0xfffd0004 w 0xc00008c1


The Linux standard serial device control can be used to set baudrate etc.

Hi,
I do not have a RS485 driver chip, is it possible to use the lines marked "RS485" on the J16 I/O Expansion as TTL level lines to talk to a PIC?
Thanks for any info

[admin]

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The signals on J16 can be used for TTL level signals only if the RS-485 driver chip is not installed.

[slonko]

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Thanks, it works 

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The Linux kernel 2.6.37 and up now includes RS-485 mode in the serial driver for the Atmel ARM processor based systems.  The user space application should use standard ioctrl function call to set the RS-485 mode.  In fact the devmem2 method to set RS-485 mode described in previous posts no longer works for Linux kernel version 2.6.33 and up.   See http://retis.sssup.it/~scordino/code/rs485.html for more information on how to use kernel built-in RS-485 mode.