Difference between revisions of "IbmPosDisplay"

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== Interface ==
 
== Interface ==
The electrical interface to the display consists of 4 wires, probably an RS485 interface, possibly:
+
The electrical interface to the display consists of 4 wires, possibly:
 
* ground
 
* ground
 
* data A (inverting), D-
 
* data A (inverting), D-
 
* data B (non-inverting), D+
 
* data B (non-inverting), D+
 
* power (12V) - red
 
* power (12V) - red
 +
 +
This is most likely an RS485 interface, because there is a 75176 (differential bus transceiver) inside the display.
  
 
A very simple RS232-to-RS485 conversion can be done by simply biasing the inverting data pin (data A) to half the supply voltage, and connecting the RS232 data line directly to the non-inverting data pin (data B).
 
A very simple RS232-to-RS485 conversion can be done by simply biasing the inverting data pin (data A) to half the supply voltage, and connecting the RS232 data line directly to the non-inverting data pin (data B).
  
 
== TODO ==
 
== TODO ==
* Are we really sure this it has an RS485 interface? (where did that idea come from?)
 
 
* Figure out baud rate
 
* Figure out baud rate
 
* Write software to control the display
 
* Write software to control the display

Revision as of 21:01, 20 March 2014

Project IbmPosDisplay
Status Initializing
Contact bertrik
Last Update 2014-03-20

In this project, an old IBM point-of-sale (POS) display is reverse engineered to display arbitrary text. The goal of this project is not entirely clear.

The display in question contains two rows of 20 characters each. The characters on the display are of the VFD type, in blue/cyan.

Interface

The electrical interface to the display consists of 4 wires, possibly:

  • ground
  • data A (inverting), D-
  • data B (non-inverting), D+
  • power (12V) - red

This is most likely an RS485 interface, because there is a 75176 (differential bus transceiver) inside the display.

A very simple RS232-to-RS485 conversion can be done by simply biasing the inverting data pin (data A) to half the supply voltage, and connecting the RS232 data line directly to the non-inverting data pin (data B).

TODO

  • Figure out baud rate
  • Write software to control the display

External links

Possible protocol descriptions: