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

[Volker]

On 12/23/-58 20:59, Rohit Grover wrote:
> Hi,
> 
> 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