3.2.2.2 Library Overview
The USB Host layer API is grouped functionally, as shown in the following table.
| Library Interface Section | Description |
| System Interface Functions | These functions make the USB Host Layer compatible with MPLAB Harmony. |
| Bus Control Functions | These functions allow the application to enable, disable, suspend and resume the USB. |
| Device Related Functions | These functions allow the application to suspend and resume the USB. Attached devices can be queried and their string descriptors can be obtained. |
| Event Handling | Allows the application to register an event handler. |
| Client Driver Routines | These functions are exclusive to the client drivers and should not be accessed by the application. |