This shield is one of the special shields. Special shields allows your Arduino board to use some capabilities your smartphone can do, like playing music, taking a picture, getting notifications, accessing the clock data and using the touch screen for various functions. Learn more from the special shields tutorial.
Clock library allows your Arduino board to get the time from the smartphone and take actions within certain time set in the sketch.
Adding #define CUSTOM_SETTINGS along with #define INCLUDE_CLOCK_SHIELD is a key that will let you unlock the Clock shield only amongst all shields and prevent 1Sheeld library from eating your memory specially for UNO board.
Sends a request to 1Sheeld application to get date and time information. (Mandatory)
There are three different ways to get time and date from the application:
1) Stating”queryDateAndTime” in the setup function and when you upload the sketch to your board the request is sent but you have the UART switch opened “uploading mode” which then all the data in the setup function will not reach to the application to do the process.
Solution: After you successfully upload the sketch close the UART switch “operating mode” then press the UNO’s reset button again.
2) Stating”queryDateAndTime” in the loop .. it will work like charm ….! But if you are working on an application that requires high data transfer between the application and your UNO so it’s not preferable as there will be a lot of unwanted requests by the function which the application already got informed of.
3) Not stating “queryDateAndTime” but after you already uploaded the sketch close the UART switch “operating mode” then choose the clock shield from the application which by that it will send the updated data to your UNO so that your board can save them into your sketch and do some actions.