8.4 Clock source
Three clock sources are available on the STM32H7B3I-DK board:
• 32.768 kHz crystal X1, for the STM32H7B3LIH6QU embedded RTC
• 24 MHz crystal X4, for the STM32H7B3LIH6QU system clock
• 25 MHz oscillator X2 for the STLINK-V3E
Note: By default, 24MHz clock of Camera and USB PHY is provided by the MCO1 clock signal.
8.5 Reset sources
The general reset of the STM32H7B3I-DK Discovery kit is active LOW. Sources of reset are:
• RESET button B1
• Embedded STLINK-V3E
• ARDUINO
®
Uno shield board through CN19 connector, pin 3
• MIPI10 and TAG connectors (Reset from debug tool)
The general reset is connected to the following peripheral reset functions:
• STM32H7B3LIH6QU MCU reset
• Octo-SPI Flash reset
• Camera reset
• LCD reset
•
Wi‑Fi
®
module reset (optional)
8.6 Board functions
8.6.1 TFT color LCD 480x272 pixels
The STM32H7B3I-DK board includes a 4.3-inch LCD touchscreen board which is connected to the RGB interface
of the STM32H7B3LIH6QU through the CN1 50-pin connector. The MB1315 LCD board uses the RK043FN48H-
CT672B TFT LCD from Rocktech with a driving system, a white LED backlight, and a capacitive touch panel. The
touchscreen controller interfaces with the STM32H7B3LIH6QU via the bidirectional I2C4 bus, since the reset of
the TFT LCD is controlled by the NRST general reset. A U14 external SDRAM is also used to store display data.
8.6.2 USB OTG HS
The STM32H7B3I-DK board supports USB OTG high-speed communication via a CN15 USB Micro-AB connector
and a U20 Hi-Speed USB 2.0 external PHY. A U25 USB power switch is also connected on V
BUS
and provides
power to CN15. The green LED LD6 is lit in one of these cases:
• The power switch is ON and the STM32H7B3I-DK board works as a USB host
• V
BUS
is powered by another USB host when the STM32H7B3I-DK board works as a USB device.
The red LED LD8 is lit when an overcurrent occurs (Higher than 500 mA).
Note: The STM32H7B3I-DK board can be powered by the CN15 USB connector at 5 V DC with 500 mA current
limitation.
8.6.3 EXT_I2C
An EXT_I2C connector socket is available on the STM32H7B3I-DK board and offers the possibility to connect
external modules via the I2C4 bus. The EXT_RESET is managed by an I/O signal from the STM32H7B3LIH6QU
MCU.
8.6.4 microSD™ card
A CN4 slot for microSD
™
card (SD 2.0 compliant) is available on STM32H7B3I-DK board and is connected to
SDOI1 interface of the STM32H7B3LIH6QU. The microSD
™
card detection is managed by the uSD_Detect
signal. When a microSD
™
card is inserted in the slot, the uSD_Detect signal level is LOW, otherwise, it is HIGH.
UM2569
Clock source
UM2569 - Rev 1
page 20/54
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