[squeak-dev] Re: Linux and ttyUSB0

David T. Lewis lewis at mail.msen.com
Wed Jun 18 02:54:09 UTC 2008

On Tue, Jun 17, 2008 at 06:11:53PM -0700, Skadge wrote:
> A better workaround, for us, would to define a new Squeak primitive in
> SerialPlugin to open the serial port which takes the full device string
> ("dev/ttyUSBx") as argument (in this case, the cross-plateform compatibility
> will have to be ensured in the Squeak code).
> Do you think it would be feasible? or do you have any other idea?


Certainly it is feasible. However, it would be difficult to actually get
the changes implemented and released in the "official" VM, simply because
of the time it would take to coordinate. So if you can build and release
the plugin yourself, then it can be done.

> or do you have any other idea?

If you are concerned with Unix/Linux platforms, you can probably just do
a change to these two lines in the sqUnixSerial.c support code:

  #define PORT_NAME_SIZE 11
  static const char serialPortBaseName[] = "/dev/ttyS0";

If you change the serialPortBaseName to the right value for your USB
device names, and modify PORT_NAME_SIZE to match, then the plugin will
probably do what you want without further modification. No, I have not
tested this, and yes it's a hack ;)

A slightly more difficult change would be to add an optional primitive for
Unix/Linux that sets the serialPortBaseName string. That would let you control
it from Squeak, and would not require any changes to the existing primitives.
If you did the changes to implement this for Unix, you would have a reasonable
chance of getting them included in future VM releases, because the changes
would be backward-compatible and would require testing only for Unix
based platforms.

Note, I have no experience programming USB ports, so I'm assuming from
your original question that the SerialPlugin actually works when connected
to a USB device rather than to a traditional serial port.


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