Datasheet

•
Program the appropriate endpoint control register and buffer control register like you would with a normal IN or OUT
transfer. Note that interrupt endpoints are only single buffered so the BUF1 part of the buffer control register is
invalid.
•
Set the address and endpoint of the device in the appropriate ADDR_ENDP register (ADDR_ENDP1 to ADDR_ENDP15).
The preamble bit should be set if the device is Low Speed but attached to a Full Speed hub. The endpoint direction
bit should also be set.
•
Set the interrupt endpoint active bit in INT_EP_CTRL (i.e. set bit 1 to 15 of that register)
Typically an interrupt endpoint will be an IN transfer. For example, a USB hub would be polled to see if the state of any of
its ports have changed. If there is no changed the hub will reply with a NAK to the controller and nothing will happen.
Similarly, a mouse will reply with a NAK unless the mouse has been moved since the last time the interrupt endpoint was
polled.
Interrupt endpoints are polled by the controller once a SOF packet has been sent by the host controller.
The controller loops from 1 to 15 and will attempt to poll any interrupt endpoint with the EP_ACTIVE bit set to 1 in
INT_EP_CTRL. The controller will then read the endpoint control register, and buffer control register to see if there is an
available buffer (i.e. FULL + AVAILABLE if an OUT transfer and NOT FULL + AVAILABLE for an IN transfer). If not, the controller will
move onto the next interrupt endpoint slot.
If there is an available buffer, then the transfer is dealt with the same as a normal IN or OUT transfer and the BUFF_DONE flag
in BUFF_STATUS will be set when the interrupt endpoint has a valid buffer. BUFF_CPU_SHOULD_HANDLE is invalid for
interrupt endpoints as there is only a single buffer that can ever be done (RP2040-E3).
4.1.2.8. VBUS Control
The USB controller can be connected up to GPIO pins (see Section 2.19) for the purpose of VBUS control:
•
VBUS enable, used to enable VBUS in host mode. VBUS enable is set in SIE_CTRL
•
VBUS detect, used to detect that VBUS is present in device mode. VBUS detect is a bit in SIE_STATUS and can also
raise a VBUS_DETECT interrupt (enabled in INTE)
•
VBUS overcurrent, used to detect an overcurrent event. Applicable to both device and host. VBUS overcurrent is a
bit in SIE_STATUS.
It is not necessary to connect up any of these pins to GPIO. The host can permanently supply VBUS and detect a device
being connected when either the DP or DM pin is pulled high. VBUS detect can be forced in USB_PWR.
4.1.3. Programmer’s Model
4.1.3.1. TinyUSB
The RP2040 TinyUSB port should be considered as the reference implementation for this USB controller. This port can
be found in:
https://github.com/hathach/tinyusb/tree/pico/src/portable/raspberrypi/rp2040/dcd_rp2040.c
https://github.com/hathach/tinyusb/tree/pico/src/portable/raspberrypi/rp2040/hcd_rp2040.c
https://github.com/hathach/tinyusb/tree/pico/src/portable/raspberrypi/rp2040/rp2040_usb.h
4.1.3.2. Standalone device example
A standalone USB device example, dev_lowlevel, makes it easier to understand how to interact with the USB controller
without needing to understand the TinyUSB abstractions. In addition to endpoint 0, the standalone device has two bulk
endpoints: EP1 OUT and EP2 IN. The device is designed to send whatever data it receives on EP1 to EP2. The example
comes with a small Python script that writes "Hello World" into EP1 and checks that it is correctly received on EP2.
RP2040 Datasheet
4.1. USB 412