Matrix Orbital PK202-25 - Manual (Page 17)

Table 8: Connector Pinout
Pin 1 +5.0 VDC (+7 to +15 VDC with wide voltage option)
Pin 2 I 2 C SCL (clock)
Pin 3 I 2 C SDA (data)
Pin 4 Ground
2.2.4 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 bytes transition. They are only capable of
failing to acknowledge the bytes following the byte, which was not 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 that 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 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 (shifted 1 bit to the left). The read
address would be 8Bhex.
For more information on Phillips I 2 C please visit;
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2.2.5 Dallas 1-Wire Bridge
The display offers one Dallas 1-wire bridge. All three headers are connected to one communication line.
A maximum of 32 1-wire devices can be connected to the display at a time.
Matrix Orbital PK202-25 13