How can I enable/disable the feed button on the SmartSource Pro?

Ranger provides an INI option that you can use to enable and disable the feed button. The option is located in a file called CapiOptions.ini.

Here's the option that you can change:

//-----------------------------------------------------------------------------------
// Feeding Section
//
// NOTE: This is only available on the SmartSource Pro.
//
// UseStartStopButton = false (default)
// true - After your application requesting StartFeeding()
// Feeding can be started and stopped by pressing the
// button on the top of the scanner.
//
//-----------------------------------------------------------------------------------
[Feeding]
UseStartStopButton=false

You can set this value by calling Ranger.SetDriverOption("Feeding", "UseStartStopButton", "true");

Ranger reads this option's value when you call Ranger.EnableOptions().