Re: Looking for Help with RS232 - USB Conversion

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Király

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Nov 14, 2010, 10:46:21 AM11/14/10
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In comp.sys.mac.apps Nelson <nel...@nowhere.com> wrote:
> I am also interested in writing my own native Mac software to access
> the meter directly.

You might find this page helpful:
http://developer.apple.com/hardwaredrivers/customusbdrivers.html

--
K.

Lang may your lum reek.

nospam

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Nov 14, 2010, 10:54:32 AM11/14/10
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In article <0001HW.C90525B1...@news.astraweb.com>, Nelson
<nel...@nowhere.com> wrote:

> I have a MacBook Pro running OS X 10.6.4 and would like to interface to
> a Craftsman Model 82325 Multimeter. �The meter has an RS 232C plug and
> the software runs under Windows. I plan to use an emulator such as
> Crossover or VMWare Fusion on the Mac to run the software and a RS232 -
> USB conversion cable to physically connect the meter. I am also

> interested in writing my own native Mac software to access the meter
> directly.
>

> I'd be interested in hearing any advice/experiences from anyone who has
> attempted a similar project. I'm not sure how the various emulators
> handle "com" ports.

iogear or keyspan. i prefer the former since it has a larger buffer and
the device is physically smaller. whatever you get be absolutely sure
there are os x drivers. i've used it to talk to gps devices and other
things that require serial ports.

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isw

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Nov 15, 2010, 1:47:25 AM11/15/10
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> I have a MacBook Pro running OS X 10.6.4 and would like to interface to
> a Craftsman Model 82325 Multimeter. �The meter has an RS 232C plug and
> the software runs under Windows. I plan to use an emulator such as
> Crossover or VMWare Fusion on the Mac to run the software and a RS232 -
> USB conversion cable to physically connect the meter. I am also
> interested in writing my own native Mac software to access the meter
> directly.
>
> I'd be interested in hearing any advice/experiences from anyone who has
> attempted a similar project. I'm not sure how the various emulators
> handle "com" ports.

I've seen two "flavors" of serial-USB adapters -- one is full-tilt
RS-232 compatible, and tends to be more expensive; the other is less
expensive and actually works just as well, but does not have actual
RS-232 line drivers and receivers built in -- and they don't bother to
mention this little detail in the accompanying literature.)

The problem is that RS-232 line drives and receivers are logical
inverters, so if they're not there, the signals will be "upside down"
and things won't work -- unless both ends happen to have the same number
of inverters (usually none, or two); in that case, things will work fine.

For almost all purposes, a non-driver type can be adapted simply by
adding CMOS inverters to the appropriate lines.

The non-inverting-no-RS-232-driver type is likely what you will get off
eBay for $2 or so (and don't ask me how I know all this).

> I'm not sure how the various emulators handle "com" ports.

I'm using a Mac "native" and the adapter shows up in /dev *only when it
is plugged in*, and the name will be assigned to it by the driver. You
may have to look in /dev to find the name so you'll know what to tell
the emulator.

Isaac

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