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Questions regarding implementing/retro fit of I-button IMMO
Have an ECU that was not built with the 1-wire interface. I'm assuming that the ECU needs the 1-wire interface, but am unsure.
Does one just need to add the 1-wire load IC? - at minimum, yes. But ...
- In the extremely unlikely case if the analog input protection on EC18/pin16 is solved with 5V1 zener towards ground, then remove the zener or the resistor (or use a higher value, min 47k resistor instead). Otherwise the 5V1 zener might load the trace too much and disturb the 1-wire bus (no damage, just might not operate properly).
- than solder the DS2480B 1-wire chip.
- check DS2480B pin1 and surrounding components on GenBoard/VerThree/Schematic
- Finally enable ButtonImmobilizer
- preferrably also install (and enable) the "HW mod - "1-wire keepalive" function (1 Mohm * 1 uF RC circuit)
- with this mod if the ECU reboots during operation (eg. overtaking) than it will continue to run without requiring touching on I-button. As always, understand the risks (and decide accordingly).
- test and learn how to use it.
- After a firmware upgrade don't touch on button until the config is uploaded (VemsTune does this automatically unless interrupted by the user), preferrably also press "Validate" and review config.