
Introduction

The driver for the BAUM Vario was made on a machine that also runs Windows98
and Jaws for Windows. Since Jaws driver for Vario uses "Emulation Mode 2" we
choose to do the same, the fact that the emulation was horribly simple to
implement was an added benefit :-) This makes it simple to use both Windows
and Linux without having to change the settings of the Vario.

If you have a need for this driver to operate in native Baum-mode, feel free
to contact the authors and we'll see what we can do.


Setting up the Vario

In order to use this driver you need to set your Vario to "Emulation Mode 2"
as follows:

1. Shut down any running software for the Vario, or the entire computer if
   you feel that's easiest.
2. Power off the Vario.
3. Power up the Vario. It should now print some status information, starting
   with the text "BAUM". Last in the display there should be information on
   which emulation-mode is in use, memorize this so you'll be able to change
   it back if necessary.
4. Change the emulation using the upper and lower buttons beside the display.
   Depending on the firmware-version the Vario can have 2-5 modes. The end
   of the display should read "Emul. 2". For some reason the dot-patterns
   doesn't seem to match real braille, so ignore the lower right dot in the
   number.
5. Save the setting by pressing the upper and lower button right or left
   beside the display simultaneously about 3 seconds. The display will then
   show "Saved".

Upon receiving data the Vario will stop displaying the status-text and display
the recieved information instead.

The Vario speaks 19200/8/O/1 in this emulation mode, so it should work with
virtually any serial-port found in a PC.

About the implementation
We managed to get hold of the protocol specifications for the Vario (Vario40
03/19/98 from Baum Products GmbH). This documentation specifies a number of
different protocols, we decided to use the "HT-Protocol", this seemed to have
the desired functionality as well as beeing straightforward to implement.

Since we lacked any real documentation of the brltty internal communication and
structures we used the existing source as a rolemodel. If something is
ill-working do tell us. 

The implementation only resends data to the display when something actually
changes in the data. This since the brltty main engine loop´s at a rapid rate
and resending the same data has no effect but to wear out the machinera it
seemed as a waste of serial signals to do so. 

One feature we ignored in the implementation of the protocol is the usage of
ACK/NAK´s for parity anity etc. This partly since we have no control of the main
application loop. If this causes you any problem, let me know and i will fix it.


Since the brltty package missed a swedish translationtable we created one. 

Authors

This driver is written mainly by Per Lejontand <pele@acc.umu.se> with some
assistance from Niklas Edmundsson <nikke@acc.umu.se>. Testing was/is done by
the owner of the Baum Vario used during development, Sabina Lundgren
<mina@acc.umu.se>.
