My project, briefly explained is a weather station that will send data periodically from an Arduino UNO (later an attiny85) to my PC for processing. I'm using a HC-05 bluetooth module to establish a serial connection to my (Linux Mint) Laptop. That all works with blueman-manager and rfcomm using gui tools manually.

So here comes the twist. Since the bluetooth module draws significant current, I will shut it down when it's not used by simply disconnecting the power to it and the sensors. Then I would like the module to wake up when the power comes on again and send the readings to the PC, automatically.

From what I read a bluetooth module can only initiate a connection in master mode. I have tried setting this with an AT command and that part works, but I don't know how to go about creating the persistent connection to my PC that will connect up again after a power loss so that I can send the next reading.

Another part of this is of course that the Laptop running Linux Mint must be able to create the serial port (or ideally use the same port) when the bluetooth module wants to send data.

I realize this question is a bit broad, but any pointers are welcome and I'm curious first of all if this is the right way of accomplishing this task.

Thank you!

  • I can't answer your question on BL but here's a suggestion: Why not use a Bluetooth Low-Energy module (like the HM-10)? These modules should be well-designed for continious low-power consumption and deepsleep capabilities. You could also use the ESP32 with onboard BLE and put that chip into deepsleep, or any other kind of ultra-low-power BLE beacon. May 13 '18 at 10:27
  • You might also find this interesting: youtube.com/watch?v=1i-6cz4KHXE May 13 '18 at 10:30
  • That is very interesting, thank you! Do you have any experience using the HM-10? I'm a little confused on how to use the AT commands on them that would initiate the sleep mode. On the EC-05 I set it by holding the button and it enters a separate mode. On the EM-10 it seems to be able to accept AT commands in "normal" mode? That would actually be much better since the Arduino could then send that command whenever it wanted without having to set it to AT mode. Can't seem to find any information on that :-/
    – miccet
    May 13 '18 at 19:01

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