Innovate Motorsports OT-2 SDK - Manual (Page 15)

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It has room for 13 bits of data, but all Innovate Devices only use 10 bits. The reason is
legacy/historical. Notice that there is no indication of data size in the one word (two byte)
payload. The first MTS devices sent 10 bit data, and sent it in bits D0 through D9. If a
device now used the upper bits, the host would have no easy way of knowing which
channels require which scale. So, for an Aux Channel, 0 (0x000) is always the minimum,
1023 (0x3FF) is always the maximum.
Note that, unlike the header word, the MSB in both bytes of this word are 0. This is to
facilitate sync/packet parsing, but it does require that the fixed 0 bit has to be removed
and the 10 bit value properly combined for use.
‘New’ Lambda/AFR Channels
A ‘new’ lambda/AFR Channel is a bit more complicated:
Word Bit
15 Bit
14 Bit
13 Bit
12 Bit
11 Bit
10 Bit
9 Bit
8 Bit
7 Bit
6 Bit
5 Bit
4 Bit
3 Bit
3 Bit
1 Bit
0
0 0 1 0 F2 F1 F0 1 AF
7 0 AF
6 AF
5 AF
4 AF
3 AF
2 AF
1 AF
0
1 0 0 L12 L11 L10 L9 L8 L7 0 L6 L5 L4 L3 L2 L1 L0
The first thing to note is bit 14 of the first word. Unlike an Aux Channel, which is always
0, in this channel type, it is always 1. This signals that the channel requires an additional
word. Like the Aux Channel, the high bits are 0 in every byte, to help distinguish it from
the header word.
Again, the idea is to facilitate parsing, high bits, think header, counting off channels, bit
14 set, grab another word for this channel… But, again, this also requires that values
sometimes be recombined. Ultimately, the channel contains three basic pieces of
information. First, a value:
Word Bit
15 Bit
14 Bit
13 Bit
12 Bit
11 Bit
10 Bit
9 Bit
8 Bit
7 Bit
6 Bit
5 Bit
4 Bit
3 Bit
3 Bit
1 Bit
0
0 0 1 0 F2 F1 F0 1 AF
7 0 AF
6 AF
5 AF
4 AF
3 AF
2 AF
1 AF
0
1 0 0 L12 L11 L10 L9 L8 L7 0 L6 L5 L4 L3 L2 L1 L0
Although our software often clips this value to 10 bits, the devices themselves do, in fact,
send a full 12 bits of information. However, depending on the circumstances, the value
represents different things (lambda, percentage of O2, and error code, etc.). So the packet
contains information about what type of information is being sent:
Word Bit
15 Bit
14 Bit
13 Bit
12 Bit
11 Bit
10 Bit
9 Bit
8 Bit
7 Bit
6 Bit
5 Bit
4 Bit
3 Bit
3 Bit
1 Bit
0
0 0 1 0 F2 F1 F0 1 AF
7 0 AF
6 AF
5 AF
4 AF
3 AF
2 AF
1 AF
0
1 0 0 L12 L11 L10 L9 L8 L7 0 L6 L5 L4 L3 L2 L1 L0
These three bits allow for seven different ‘functions’, or data meanings: