[oopic] Re: Serial Port....Power...OOPIC-R

--- In oopic@yahoogroups.com, "aravind_2917" <aravind_2917@...> wrote:
>
>
> hello,
>
> Am planning to buy a serial bluetooth adapter(FireFly,www.sparkfun.com)
> to connect it to the serial port of an oopic-R board.
>
> The specifications of serial bluetooth adapter says that the adapter
> accepts power from PIN 9 OF THE DB serial port if available,or it should
> be powered externally.It requires 5 V DC.
>
> Will this work with oopic?...Does OOPIC supply power on pin 9 of the
> serial port?..Its a problem to power the serial adapter externally..
>
> so,should i go ahead and buy it?
>
> thank you.
>

From the schematics (www.oopic.com -> Manual -> Connectors and
Mechanical -> click on R-board -> Schematics) you can see that pin 9
is jumpered to pin 8. Kind of strange...

This jumper could cause you a lot of trouble even if you use an
external power supply to plug in to the adapter. You will be
back-feeding pin 8 with a high voltage and the adapter might not like it.

If you wish, you could make a short adapter cable that didn't carry
pin 9 to the female of the cable adpater. This would allow you to use
a power supply at the bluetooth gadget or connect it to the female of
the cable adapter. Carry only pins 2,3 and 5 from the OOPic (more
below...).

You are also going to have to deal with RTS/CTS. The OOPic doesn't
provide these signals. In the adapter cable you build, jump pins 7 &
8 at the end where the dongle plugs in (female). See the last
paragraph of Page 7 (PDF page 2).

The OOPic doesn't handle serial IO very well. You could try to
implement flow control with the IOLineF property of oSerialPort. You
would need to level shift the IOLine (MAYBE a transistor and resistor)
connecting to pin 8 (remove jumper from pin 7) of the female end.

Then there is the issue of level shifters in general: the OOPic R
doesn't provide true RS-232 levels. There is a remote possibility
that the dongle won't like 0V and 5V levels. I don't think it will be
a problem but it might.

All of this leads to my conclusion that the S-board is a better way to
go. I can easily add a level shifter that produces ALL of the signals
and all at the proper voltages
http://www.pololu.com/products/pololu/0126/

It's also true that I
MUST add a level shifter, nothing is included.

Richard

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