Matrix Orbital GLK24064-25 Legacy - Manual (Page 18)

3.4 There is a problem uploading fonts or bitmaps.
• First, ensure that you can communicate to the display. A good test is to use a PC, with MOGD# in-
stalled, to connect to the display. See Section 1.4 on page 3 for setting up a PC to test the GLK24064-
25.
• Second, unsure that the File System Lock Jumper has not been set. See Section 2.4 on page 9.
• Third, please ensure that the display module’s memory is not full. The GLK24064-25 has 16 Kb of
memory for fonts and bitmaps.
NOTE If you are unable to resolve any issue please contact Matrix Orbital. See 15.6 on
page 63 for contact information.
4 Communications
4.1 Introduction
The commands listed in this chapter describe how to configure data flow on the .
4.1.1 I 2 C Communication Summary
The 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 to inform the
module that its responses are to be output via I
2 C. This can be done by sending command 254 /160 / 0 to
turn off auto transmission of data in RS232. This will keep the data in the buffer until the master clocks
a read of the slave. The I
2 C data lines operate at 5V normally or 3.3V for -1U style units. The uses 8-bit
addressing, with the 8th or Least Significant Bit (LSB) 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. This address may be changed by using cmd 254 / 51 /
2 C master wishes to write
to the display, the effective address is $50 (0101 0000) , since the LSB has to be 0 for an I 2 C master write.
When the I 2 C master wishes to read the , the effective address is $51 (0101 0001), since the LSB has to be
1 for an I 2 C master read.
If we take a standard Phillips 7 bit address of $45 (100 0101), Matrix Orbital’s would describe this
Phillips I 2 C address as $8A (1000 1010). The read address would be $8B (1000 1011).
The unit does not respond to general call address ($00).
When communicating in I
2 C the 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
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