# App usage
# Start/Stop the Study
The smartphone app consists of configuration screens that are controlled by the study supervisor and the study screens that are controlled by the participant. The access to the configuration screen is locked by a pin code that is configured in your Study running block in the sampling of your study.
To start the study the following steps should be done:
- movisensXS will appear in your application drawer. Select it to launch the application.
- Select Couple Device and take a photo of the QR-code of a participant that is shown in the participant tab of your study.
- After coupling is finished you can start the sampling by pressing Start Study.
- The default home screen should appear.
- Now you can put your device on standby and wait until your sampling scheme notifies you.
To stop the study the following steps should be done:
- On the home screen press the "menu" button on your phone. Press the option Configure Study. You have to enter the pin code that is configured in your Study running block in the sampling of your study.
- You can stop the study or upload the results when you have an internet connection.
# Fetch study changes on your participants' devices
As movisensXS is a tool designed to work offline and only the couple and result uploading processes need internet the changes you make to your study aren't propagated automatically on the devices. Participants need to actively synchronize the study in order to receive all the changes, else they run with an older version of your study.
To synchronize the changes the following steps should be done:
- On the home screen press the "menu" button on your phone. Press the option Configure Study. You have to enter the pin code that is configured in your Study running block in the sampling of your study.
- You can synchronize the study when you have an internet connection. You can start the synchronization by pressing Synchronize.
- After synchronizing the study you can restart the sampling by pressing Start Study.