Innovate Motorsports OT-2 SDK - Manual (Page 36)

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Expert Modes
As mentioned earlier, Expert Modes are entered using the ‘e’ command from Setup
Mode. They are specialized ‘sub modes’, each dedicated to one of the main three physical
transports for OBD-II. Mode 1 is for CAN protocols, Mode 2 is for J1850 protocols, and
Mode 3 is for ISO (K line based) protocols.
Note: If you plan on using the Expert Modes, you really should know more than me
about OBD-II protocols and standards. Frankly, that is not all that hard a bar to clear, but
it is high enough that there is no reason to mess around with tutorials and online articles,
you really need to go to the standards themselves. The two primary sources are the
Society of Automotive Engineers (SAE):
http://www.sae.org
The International Organization for Standardization (ISO), and the International
Electrotechnical Commission (IEC). Standards from the later two can normally be
obtained through the American National Standards Institute (ANSI):
http://www.ansi.org/
Overview
Assuming you are already an OBD master, we can go over some basics that all three
Expert Modes share. First, like the Setup Mode, there is a watchdog timer running. 10
seconds without activity and you get the boot. Like Setup Mode, you can prolong the
agony by periodically sending a null command (0xFF). However, unlike Setup Mode,
you will get a one byte response (also 0xFF). The reason for this is that the Expert Modes
often return variable length results, so you want to be careful to stay in perfect sync.
Another significant difference between the Expert Modes and Setup Mode is that, if
additional MTS compatible devices are attached to the OT-1b/2 Serial IN, MTS packets
will flow to the OT-1b/2 Serial OUT. However, the channels associated with the OT-1b/2
will be ‘0’ (since the unit is not polling OBD-II):