As a rule DSMC1 cameras employs the Schmitt trigger and DSMC2 employs Momentary Ground (same as Arri).
This circuitry is now located in DSMC2 modules - not the brain. Note that the Base Expander uses the old technique (3v3 Schmitt Trigger), whereas all other DSCM2 modules use the 'newer' Momentary Ground trigger.
Red have released a new version of their base expander recently. It doesn't say 'base expander' on the module and it triggers on the Arri style.
All RTMotion kits should be able to trigger both methods. Latitude uses the same camera cable for both DSMC and DSMC2 cameras.
MK3.1 receiver you will need to order a specific DSMC2 cable that we now have shipping. https://teradek.com/collections/teradek-rt-carte#accessories Part no;11-1396
In addition to this please make sure;
1. You have the correct camera selected in the menu of the MK3.1 Controller.
2. You have changed your serial communications setting on the camera to RCP (Redlink Command Protocol) You can do this via;
SETTINGS - SETUP - COMMS - SERIAL - RCP (DSMC)
SETTINGS - COMMS - SERIAL - RCP (DSMC2)
3. You have the correct GP/IO settings in camera.
Schmitt trigger - High - Start, Low - Stop
Arri style (Momentary Ground) trigger - High - Key disabled, Low - Record toggle.