 Hello, and welcome to this presentation of the STM32L4 USB 2.0 full-speed interface. It covers the features of this interface, which is widely used to interface with a PC. This slide explains the scope of this chapter within the STM32L4 product lines. As can be seen in this table, this presentation describes the USB 2.0 full-speed device interface, supported in STM32L452-462 and STM32L432-442-433 for 43 devices. This figure shows the connections between an STM32L4 microcontroller and a USB connector. The STM32L4 features a USB 2.0 full-speed communication interface, allowing the microcontroller to communicate typically with a PC. The simplest implementation is a USB peripheral device. It provides a 16-end point capability, which can be configured, for example, as eight bi-directional end points. It also supports the battery charging detection specification, version 1.2. Application benefits include crystal-less operation, a low-power implementation, and faster charging, thanks to the charger detection function. Let's look at some of the key features of this USB full-speed interface, which is a USB 2.0 compliant interface that operates at a 12 megabit per second bit rate. A USB FS device can be implemented. Crystal-less operation is supported. A total of 16 end points, eight bi-directional, can be supported. Full support for isochronous end points. Bulk end points are able to use a double-buffering mode offering higher performance. Inbuilt support for link power management adds enhanced power modes on top of the USB 2.0 specification. Battery charger detection allows for increased current to be drawn from BCI 1.2 compliant chargers, allowing up to 1.5 amp charging. The block diagram of the USB full-speed device controller shows the various building blocks inside, along with its analog transceiver, which manages the physical layer shown above. The physical layer, or FI, handles the analog signal levels, including specific level detections as well as battery charger detection functions. The USB interrupt goes to the Cortex processor to signal various USB events. The AHB peripheral bus, or APB, enables read-write access of the controller. Other key elements are the packet buffer memory and the suspend driver, allowing low power operation. Several related peripherals work in conjunction with the USB device controller to link the USB activity to the system power mode and the requirements of the software. The clock recovery system allows operation without an external crystal using the integrated HSI oscillator as the main clock source. The interrupt events are sent to the non-vectored interrupt controller via a single line. The system events can cause the system to wake up from stop mode, for example, at the moment we resume from USB suspend mode. The USB device controller generates interrupts in different circumstances, which generally require handling by software. The first two listed interrupts cover various error and warning conditions. The remaining interrupts correspond to normal USB protocol events. The USB peripheral is fully active in run mode. After a suspend event, sleep mode and also stop zero and one modes are available. Stop two and standby mode should not be used. Some debug help is available using a single status bit which corresponds to an interrupt event. Within the USB device controller, the dedicated ERR status bit provides some debug functionality in a USB application in relation to various events. The events that can trigger this debug bit are listed in this table. There is also a way to directly read the states of the D plus and D minus lines. Here is an application example of a low power peripheral device. Power is drawn directly from the USB Vbus signal. No crystal is required. For complete USB specification documents, please refer to usb.org. The USB 2.0 document home page has a zip file containing the USB 2.0 and OTG 2.0 specifications and an engineering change notice or ECN for link power management or LPM. The USB device class documents page has the battery charger specification. Additional information can be found in these application notes.