having trouble receiving serial data using my USB->serial adaptor

[Rohit Grover]

Hi,

Thanks for the response. I stumbled upon the solution quite by chance.

My USB->serial adaptor has a NULL modem built into it, so attaching an
external NULL modem was un-necessary and incorrect. It is a wonder that the
devices survived this treatment.

thanks again.

regards,


>
> > I am having trouble getting my BAFO 810 USB->serial adaptor to
> > work. I have built the uplcom and ucom drivers into the kernel,
> > and my USB->serial adaptor is recognized at boot, as can be
> > inferred from the following lines from /var/run/dmesg.boot:
> >
> > ucom0: <Prolific Technology Inc. USB-Serial Controller, class
> > 0/0, rev 1.10/3.\ 00, addr 2> on uhub3
> >
> > I am using minicom to drive /dev/cuaU0 at 115200 8N1.
> >
> > If I connect the Tx and Rx lines (pins 2 and 3) of the DB9
> > connector, I can get echoes of my keystrokes on the minicom
> > terminal.
> >
> > Unfortunately, I am unable to connect to an embedded device which
> > supports serial connections at 115200 8N1. When I plug the serial
> > output connector of my adaptor to a NULL modem and then to the
> > target embedded system, I don't see any serial output from the
> > device on my minicom terminal. This same device communicates
> > correctly with the serial port of my linux desktop with minicom
> > and 115200 8N1.
> >
> > As a further experiment, I manually connected pins 2,3, and 5 of
> > the serial end of my adaptor to pins 3,2, and 5 respectively of
> > the embedded device, but still no luck.
> >
> > What am I missing?
> >
> > regards,
> >
>
>
> Rohit,
>
> hard to tell on the distance but if you're able to receive (using a
> loopback adapter), it sounds like either side is most likely requiring
> hardware handshake (DSR/DTR, RTS/CTS).
>
> Sometimes it helps to short cut the DCD line (to RTS/DSR), as some
> device refuse to send if DCD is not set. If you're owning a break out
> box, it should be snap to figure that out. At least you should check
> using a serial line tester (those little tools signaling line status
> using LEDs or use a Voltmeter to check for correct line status).
>
> Volker
>