[oopic] Re: Serial IO with ooPIC-R

--- In oopic@yahoogroups.com, "rtstofer" <rstofer@...> wrote:
>
> --- In oopic@yahoogroups.com, "design.wonk" <design.wonk@> wrote:
> >
> > Greetings,
> >
> > I have an ooPIC-R that I am planning to use to control an audio
> > installation. The ooPIC will be used to drive a Daisy MP3 player
> (kit
> > from Make magazine). I am familiar with RS232C types of serial
> > connections, but this type of serial IO is new to me. The Daisy
> has a
> > serial control interface with TX and RX pins. I will be providing
> > power to the Daisy using one of the regulated connections on the
> ooPIC.
> >
> > This is the diagram of the serial pins on the target device.
> > <http://tangentview.com/images/schem.png>
> >
> > My question is how do I wire these two boards together. The
> grounds
> > should be linked by the power configuration, but how many other
> wires
> > are needed? Which ooPIC objects should I be using? I am just not
> sure
> > about timing and flow control.
> >
> > thanks
> >
> > -Ray
>
> From the schematic, the device doesn't offer flow control. If the
> OOPic has to RECEIVE information from the device and the messages are
> more than about 4 chars at almost any slow baud rate, this project
> ain't happening. We've been talking about this almost continuously
> for the last two weeks.
>
> Unfortunately, the OOPic R has an RS232 level shifter built in.
> Also, unfortunately, it isn't real RS232. Probably the easiest thing
> to do is shift the levels of your device and plug it into the OOPic
> DB-9 connector. Use a level shifter like
> http://www.pololu.com/catalog/product/126

Connect the device Rx line
> to the level shifter Tx and vice versa. You can ignore the other
> signals but you do need to provide power and common ground.
>
> Now, since the OOPic has a female connector and the level shifter
> also has a female connector, you need a male-by-male null modem to
> make the connection. See http://www.cablesforless.com/index.asp?
> PageAction=VIEWCATS&Category=428 Use oSerialPort
>
> If the OOPic really doesn't need to receive anything, you can use
> oSerialL and just connect the OOPic output pin (pick one) to the
> device Rx line.
>
> Richard
>

Richard,

Thanks for the information. The ooPIC does not need to receive
any information from the mp3 device and will be sending 2 char
commands, so it looks like I am OK with the oSerialL. Regarding
linking the grounds - if I am providing power to the mp3 device from
the ooPIC-R do I need to do anything else to have a common ground?

thanks

-Ray

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