Matrix Orbital VK204-25 Legacy - Manual (Page 20)

ohm meter, try using a different power cable, if this does not help try using a different power supply.
• The last step will be to check the Power / Data Connector on the VK204-25. If the Power / Data
Connector has become loose, or you are unable to resolve the issue, please contact Matrix Orbital,
see 14.5 on page 56 for contact information.
3.2 The display module is not communicating.
• First, check the communication cable for continuity. If you don’t have an ohm meter, try using a
different communication cable. If you are using a PC try using a different Com Port.
• Second, please ensure that the display module is set to communicate on the protocol that you are
using, by checking the Protocol Select Jumpers. To change the protocol used by the display module
see Section 2.3 on page 11.
• Third, ensure that the host system and display module are both communicating on the same baud rate.
The default baud rate for the display module is 19200 bps.
• If you are communicating to the display via I 2 C please ensure that the data is being sent to the correct
address. The default slave address for the display module is 0x50.
NOTE I 2 C communication will always require pull up resistors.
• Finally, you may reset the display to it’s default settings using the Manual Override Jumper, see
Section 2.6 on page 13.
3.3 The display module is communicating, however text cannot
be displayed.
• A common cause may be that the brightness settings have been set to low. The solution to this problem
is to increase the brightness.
4 Communications
4.1 Introduction
The commands listed in this chapter describe how to configure data flow on the VK204-25.
4.1.1 I 2 C Communication Summary
The VK204-25 is capable of communicating at 100 KHz in I 2 C mode, with 127 units addressable on a
single I 2 C communication line. However, in order to communicate via I 2 C you must first ensure that pull up
resistors, with a nominal value of 1K to 10K, are placed on the SCL and SDA communication lines coming
from pins two and three of the Data / Power Connector respectively. Data responses by the module are
automatically output via RS232, in case the host will be querying the module, it is necessary for the host
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