Why can't I use an external switch with inverse scanning or automatic step scanning?

To support any access method where the app needs to know when the user both presses and releases the switch, the app needs to get two signals from the switch: the first when the switch is pressed, and the second when the switch is released. It is possible to get both of these signals from the touch screen of the device. For external switches connected via a Bluetooth switch interface, the app only receives the first signal: when the switch is pressed. There is no way for the app to know when the switch is released, so there is no way to support any access method that needs to know how long the switch is held for. If switch interfaces are developed that send both the press and release signals to the app, then AssistiveWare will have the ability to support Inverse and Automatic Step Scanning modes with external switches. At the moment we are not aware of any such switch interfaces, so these scanning modes require the user to use the screen as a switch.

If you have any questions, please email us at support@assistiveware.com for further assistance.

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