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I'm trying to connect a XS3868 Bluetooth module to an Arduino. This is what the module looks like, the picture includes the pin names. the pin names I also found the following diagram online that explains how to wire it: the circuit diagram

There a couple of symbols in that diagram that I don't understand though:

  • What does the symbol indicated in red and the 47u or 220u next to it mean?
  • What is the part of the circuit indicated in blue trying to do? Why is there a capacitor?

Thanks for your help!

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    \$\begingroup\$ Help I've gone colour blind - I see no red or blue symbols. \$\endgroup\$ – JIm Dearden Oct 25 '16 at 19:48
  • \$\begingroup\$ @Jim It must contagious.. \$\endgroup\$ – m.Alin Oct 25 '16 at 19:50
  • \$\begingroup\$ @JImDearden That was dumb... I have edited my post to include the correct picture. \$\endgroup\$ – Todd Sewell Oct 25 '16 at 19:52
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    \$\begingroup\$ Red : electrolytic capacitors. Connect them right way round. Blue : hold the Reset pin low to reset the CPU on power-up \$\endgroup\$ – Brian Drummond Oct 25 '16 at 19:52
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Red = polarized capacitor. The 47u = 47 microfarads. Blue = poorly drawn, but the 220uF cap is likely the output cap for the internal 1.8V regulator. The 10K + 100nF cap are an RC to keep the device in reset until the 1.8V output is stable.

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  • \$\begingroup\$ What do you mean by "output cap"? \$\endgroup\$ – Todd Sewell Oct 25 '16 at 19:55
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    \$\begingroup\$ @ToddSewell, Your board has "input" from a battery, Vbat. Low left corner has a LDO voltage regulator, which apparently produces 1.8V "output". That's why the 220uF cap is called "output cap". And please don't ask what "LDO" means. \$\endgroup\$ – Ale..chenski Oct 25 '16 at 20:00

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