I need a voltage source for an external peripheral on my STM32 dev kit. (Reference manual available here.) I see from looking at the extension pins that there are two types of power pins: APP and EMU. (E.g. EMU_3V3 page 22, APP_3V3 page 23.)

What does EMU and APP mean? What is the difference between the pins? Which one should I use to power an external temperature sensor?

  • \$\begingroup\$ The pins seem to belong to the connector for daughter boards, and I think are regulated voltage outputs. What kind of temperature sensor are you going to use? \$\endgroup\$
    – clabacchio
    May 16, 2012 at 9:03

1 Answer 1


APP_3V3 is connected to the eval board's 3.3V rail.

EMU_3V3 does not actually seem to be connected anywhere, from what I can glean from the schematic (well, the two connectors are connected together, but that's it).

You can get the answers you're asking about from looking at the (frankly pretty horrible) schematic of the eval-board.
Fortunately, the schematic is saved as a vector-file, rather then images, so you can search for net-labels in the PDF. The only place EMU_3V3 crops up at all is on CN1 and CN3.

Note that this is a pretty freaking terrible schematic. There are multiple power nets, that are connected together. As such, D5V and EMU_5V are really the same net. The same is true for APP_VCC, +3V3, and APP_3V3, which are also all tied together.


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