Hardware layout and configuration
UM2032
16/40
UM2032 Rev 3
5.3.4
Supplying the 32F412GDISCOVERY through
the ST-LINK/V2-1 USB port
To power the 32F412GDISCOVERY through the ST-LINK/V2-1, the USB host (a PC) gets
connected with the 32F412GDISCOVERY Micro-B USB receptacle CN6, via a USB cable.
This event starts the USB enumeration procedure. In its initial phase, the current supply
capability of the USB port located on the host, is limited to 100 mA. It is enough because
only the ST-LINK/V2-1 part of the 32F412GDISCOVERY Discovery kit draws power at that
time. If the solder bridge SB18 is OFF (default configuration), the U8 ST890 power switch is
set to OFF position, and only the ST-LINK/V2-1 is powered. In the next phase of the
enumeration procedure, the host PC informs the ST-LINK/V2-1 facility of its capability to
supply up to 500 mA of current. If the answer is positive, the ST-LINK/V2-1 sets the U8
switch to ON position to supply power to the remainder of the 32F412GDISCOVERY
Discovery kit. If the PC USB port is not capable of supplying up to 500 mA of current,
another power source should be used like VIN pin of connector CN2.
Should a short-circuit occur on the Discovery kit, the power switch protects the USB port of
the host against current demand exceeding 600 mA. In such an event, the red LED FAULT
LD10 lights on.
The 32F412GDISCOVERY Discovery kit can also be supplied from a USB power source not
supporting enumeration, such as a USB charger. In this particular case, SB18 solder bridge
must be ON. ST-LINK/V2-1 turns the power switch ON regardless of the enumeration
procedure result and passes the power unconditionally to the Discovery kit.
The green LED LD6 turns on whenever the Discovery kit is powered.
