[uClinux-dev] Controlling DTR

Mark McChrystal mark_mcchrystal at yahoo.com
Wed Nov 28 17:28:10 EST 2001

Does the uCdimm hardware support DTR?  Most embedded
hardware designers save CPU GPIO pins by having a
minimal serial port--sometimes only rx and tx.  From
the serial code from the 2.4 tree:

/* Sets or clears DTR/RTS on the requested line */
static inline void m68k_rtsdtr(struct m68k_serial *ss,
int set)
        if (set) {
                /* set the RTS/CTS line */
        } else {
                /* clear it */

I would guess that there's no hardware there to
support DTR (like the ucsimm) so you will need to use
a gpio pin hooked up to a RS232 driver and modify

--- Rob Norman <rjnorman at pacbell.net> wrote:
> Hi.
> I'm talking to a wireless modem that requires DTR
> and I'm  feeling a bit stuck being new to Linux and
> not familiar with serial control protocols.  I've
> got code that talks to the serial ports of my uCdimm
> but cannot figure out how to control the DTR  which
> is sitting at ground.  I've looked at code examples
> in minicom but can't decipher  what options are
> appropriate to my module.  I'm on a tight schedule
> and would appreciate some help here.
> I'm using system IO to talk to the modem --- open,
> read write.  Is there a better way to access my
> modem?
> Thanks in advance
> Robert Norman
>  www.acpropulsion.com

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