2008-12-11 11:08:39 RS485 style implementation

Gil Richard (CANADA)

Message: 66633

I am adding RS485 support to the bfin_5xx.c module and am grappling with an implementation issue. The application would make a driver call to toggle between RS232 and RS485 operation, but should that driver call be implemented as an ioctl() call or a termios() call? Or perhaps a third option I haven't thought of?

-Gil

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2008-12-11 11:11:20 Re: RS485 style implementation

Mike Frysinger (UNITED STATES)

Message: 66634

off the top of my head, no termios setting is applicable ... so make it a custom ioctl()

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2008-12-11 11:58:12 Re: RS485 style implementation

Ian Jeffray (UNITED KINGDOM)

Message: 66636

I've also had to add RS422/RS485 handling and switching for a project, along with automatic control of the CTS line when requested via CRTSCTS. There may be a way I can merge these options in to the stock driver. Anyway, for RS485 switching, to bfin_serial_pops I added .ioctl = bfin_serial_ioctl. bfin_serial_ioctl() just responds to cmd == TIOCSERSETRS485 and does the toggle:

if ( cmd == TIOCSERSETRS485 )

{

int is485;

if ( get_user(is485, uarg) )

return -EFAULT;

// Prod your hardware here

TIOCSERSETRS485 is the name used for the toggle on other architectures, so I defined it in asm-blackfin\ioctls.h thus:

#define TIOCSERSETRS485 0x5461

Then you can call it from your userland app: int is485=1; ioctl(fd, TIOCSERSETRS485, &is485);

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2008-12-11 13:15:45 Re: RS485 style implementation

Robin Getz (UNITED STATES)