Matrix Orbital PK162-12 - Manual (Page 18)

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 11.
3.3 The display module is communicating, however text cannot
be displayed.
• A common cause may be that the contrast settings have been set to low. The solution to this problem
is to adjust the contrast settings. The default setting that will work in most environments is 128.
NOTES
• Optimal contrast settings may vary according to factors such as temperature, viewing
angle and lighting conditions.
• If you are unable to resolve any issue please contact Matrix Orbital. See 14.5 on
page 55 for contact information.
4 Communications
4.1 Introduction
The commands listed in this chapter describe how to configure data flow on the RS232/TTL and I 2 C
port.
4.1.1 I 2 C Communication
The PK162-12 is capable of communicating at 400 Kbps 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 set the Protocol
Select Jumpers as can be seen in Section 2.3 and ensure that pull up resistors, with a nominal value of 1K to
10K, are placed on the SCL SDA communication lines coming from pins two and three of the Data / Power
Connector respectively. The PK162-12 uses 8-bit addressing, with the 8th bit designated as the read write
bit, a 0 designates a write address and a 1 designates a read address. The default read address of the display
module will be 0x51, whereas the write address is 0x50 by default, to change the I
2 C address see section
8.2.1.
When communicating in I 2 C the PK162-12 will send an ACK on the 9th clock cycle when addressed.
When writing to the display module, the display will respond with a ACK when the write has successfully
been completed. However if the buffer has been filled, or the module is too busy processing data it will
respond with a NAK. When performing a multiple byte read within one I
2 C transaction, each byte read from
the slave should be followed by an ACK to indicate that the master still needs data, and a NAK to indicate
that the transmission is over.
Matrix Orbital PK162-12 14