Chapter 5 Control Circuity And Hardware Modules; Introduction To The Chapter; Reset; Clocks - OLIMEX STM32-H405 User Manual

OLIMEX© 2016 STM32-H405 user's manual

CHAPTER 5 CONTROL CIRCUITY AND HARDWARE MODULES

5. Introduction to the chapter

Here you can find information about reset circuit and quartz crystals locations, the power supply
circuit is discussed.

5.1 Reset

The reset circuit is connected to pin #7 (NRST) of the STM32F405RG microcontroller. STM32-
H405's reset circuit includes R8 (10 kΩ), C19 (100nF) and a RESET button.
The reset signal is also available on pin #25 of the EXT1 header. It is also available at pin #15 of the
JTAG connector.

5.2 Clocks

There are two quartz crystals available on the board:
8 MHz quartz crystal Q1 is connected to pins 5 and 6 of the ARM microcontroller.
Quartz crystal Q2 is a 32768Hz RTC (real-time clock) and it is connected to microcontroller's pins
3 and 4.

5.3 Power supply circuit

The power supply circuit of STM32-H405 allows the board to be powered by three sources.
The most used interface for powering is the USB type B connector. It works at 5V DC.
The board can also be powered via the on-board JTAG connector. In that case the board receives
3.3V DC from the debugger tool.
Finally, the board can be powered from the EXT headers. The best location to power the board
would be pins #26 (+5V DC) and #26 (GND) from the EXT2 connector. Double check the pin
locations before providing the power.
The board consumes around 0.2W (e.g. 0.04A at 5V) with both LEDs on.
By default, if you have successfully powered the board both LEDs would turn on. In case you you
have modified the software the green LED might not turn on since it is initialized by the code
loaded on-board. The red LED should always turn on upon powering. Note that it is possible to
have the PWR LED on even if there isn't enough power for proper operation of the board and all the
peripherals currently connected.
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