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!

  • 2
    \$\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
  • 2
    \$\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

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.

  • \$\begingroup\$ What do you mean by "output cap"? \$\endgroup\$ – Todd Sewell Oct 25 '16 at 19:55
  • 1
    \$\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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.