Re: Serial port


"John Fields" <jfields@xxxxxxxxxxxxxxxxxxxxx> wrote in message
news:e5if71ho936s527tv5knog655ffr0i7tpu@xxxxxxxxxx
> On 3 May 2005 09:43:42 -0700, frb78@xxxxxxxxx (Fred) wrote:
>
>>After my question on the parallel port, I must ask you something about
>>the serial port. Why I cannot see on my scope the data signal if I put
>>my scope directly to the pins. To see it, I must connect the serial
>>port on an other device and then, put the scope on the line.
>
> ---
> Connect your scope ground to SIGNAL GROUND in the serial port
> connector and then connect the probe input to either RX DATA or TX
> DATA. Center your trace and set the vertical sensitivity to something
> like 5 volts per box. Set your sweep speed for a convenient display
> of the data rate you're expecting and set the sync to auto.
>
> That should get you started, and then you can fiddle with the settings
> all you want. Be aware that you'll be looking at data constantly
> changing in time, so unless you're sending (or receiving) a repeating
> pattern and you can get the sweep speed and sync set up just right you
> won't see a stable display.
Key thing missing here, is to go into device manager, select the port,
select the setup options, and 'advanced', and set 'flow control', to
'none'. If this is not done, the port will usually default to using
hardware flow control, and data won't be sent, unless the right flow
control lines are 'made'. With this done, you should be able to type data
in a terminal program, and see the serial data on the scope.

Best Wishes


.

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