OLIMEX© 2015
STM32-P405 user's manual
3.3 Powering the board
The board can be powered in one of the following ways:
1) Using the JTAG or SWD debugger – the board gets powered via the 20-pin 0.1” step JTAG connector;
note that some tool might hold the board in RESET state – make sure to release the microcontroller from
RESET to be able to see the execution of your code
2) Using USB cable – the board gets powered via the USB connector; the power is provided, typically, by
your computer's USB port
3) Using external power supply – in this case, the board gets powered via the VIN line – p6V DC
to pin (pad) named “VIN”; then connect the power supply's ground line to a pin (pad) named “GND”.
The board has BAT_3V connector which can be used to keep alive the RTC, external clock 32 kHz
oscillator and backup registers (through power switch) when VDD is not present. BAT_3V requires
voltage in the 1.65V – 3.6V range! The BAT_3V connector can not be used to fully power the board.
IMPORTANT: By default you can have either battery or external power supply connected (via the 6V DC
barrel jack). If you connect both you might damage the board or the battery. If you need to keep the
physical connection consider changing the default (closed) position of the BAT_E jumper!
3.4 Programming the board
The programming of the board is also fairly straight forward (unlike the software development for the
board).
3.4.1 Using JTAG debugger
This is the recommended method of changing the software of the board. This is fairly simple from
hardware point of view – simply plug the male 20-pin JTAG connector of your hardware tool to the 20-
pin female JTAG connector of STM32-P405.
Refer to the documentation of your debugger and also to the documentation of the software of choice on
instructions how to set the whole development environment.
3.4.2 Using USB cable and bootloader software
The board can be programmed without a debugger tool. In this case you only need a personal computer
that is able to run Windows software and an USB cable.
STM32-P405 has a built-in USB DFU bootloader that allows such programming.
Programming STM32-P405 via the bootloader is a slow process that requires the re-configuration of
SMD jumper. It is not recommend for initial evaluation, research and development (use any ARM JTAG
debugger instead). Using the bootloader might be good idea only if you need to program the board once
or twice.
How to do it:
1. Change the position of one of the boot SMD jumpers – B0_H/B0_L (the bottom one). By default it is
set to position B0_L – you need to change it to B0_H. This requires soldering.
Page 11 of 31
