Matrix Orbital GLK12232-25-WBL - Manual (Page 11)

Table 3: Connector Pinout
Pin 4 Ground
Pin 3 SDA (I 2 C data)
Pin 2 SCL (I 2 C clock)
Pin 1 Vdc
2.1.4 ACK
The idea of ACK is to indicate when the data has been received correctly. ACK does not indicate data
incorrectly received. ACK simply fails to indicate when data is correctly received. Clearly, this is of limited
usefulness and even less so with Matrix Orbital modules. Matrix orbital modules are not capable of failing
to acknowledge an incorrectly received byte in response to that byte’s transition. They are only capable of
failing to acknowledge the bytes following the byte, which weren’t received. To fully understand the reasons
for this one needs to understand something about how a Matrix Orbital module processes data. Basically the
reason why a Matrix Orbital module might fail to receive a byte correctly is that it was unable to process the
byte previous before the failed byte was transmitted. Because the module cannot possibly know that it would
be unable to store the byte before the next byte was received it cannot know to not ACK. The reason for this
situation in deference to situations one might be familiar with (i.e., memory chips, etc) is that the Matrix
Orbital module employs a micro-processor to perform these data storage functions. A memory chip takes
care of these things entirely within hardware subsystems which operate at the same speed as the transmission
themselves.
The display uses a standard Phillips 7bit address as defined by Phillips. However, Matrix Orbital specifies
I 2 C address in 8bits. The 8th bit, least significant bit (LSB or Low Order Bit) of the 8bit address is a read
/ write bit. If we take a standard Phillips 7bit address of 45hex this would be in binary; 1000101. This is
7bits. Matrix Orbital would describe the Phillips I
2 C address of 45hex as 8Ahex. The read address would
be 8Bhex.
For more information on Phillips I 2 C please visit;
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2.2 General Purpose Outputs
The display has two general purpose outputs, G1 and G2. These are provided to conthttp://www.atmel.com/dyn/resources/prod_do
relays or other electronic devices. This allows external devices to be turned on or off using the PC or con-
troller and software commands.
The two outputs differ slightly in specification;
• G1 provides an output which is switched LOW when ON. When G1 is OFF it is pulled up to +5V
through 150 kohms, in other words it can only be used to ’ground’ an external device. Maximum
current is 20 mA.
• G2 provides an output which is switched LOW when ON. When G2 is OFF it is pulled up to +5V,
supplied by the module. Maximum current is 20 mA.
Both outputs are referenced to ground.
Typical use of these outputs is shown in the Figure below.
Matrix Orbital GLK12232-25-WBL 7