I was able to connect my HC-05, pair it with my phone, and I can see data in the Serial Bluetooth Terminal Android App. But when I try to connect it to a certain application it says it cannot find it. Can the application force a certain version of Bluetooth? Am I missing something? Thanks.

  • What to you mean by a "certain application"? Does the app (Android side) say it can't see the HC? Does the HC say it can't send data? More details please :)
    – Peter
    Feb 22, 2019 at 11:19

1 Answer 1


The HC-05 modules use bluetooth 2.0. Certain apps would only be compatible with bluetooth 4.0 devices (BLE - Bluetooth Low Energy), such as an HM10 or AT09.

It could be that your app requires the device to use v4.0+. Are you able to find, and pair with the device using your android's default bluetooth device scanning/pairing features?

Assuming that your app does not require v4.0+, have you removed the connection from 'en'/'ch_pd' to 3.3v? If that was still connected (which is a required connection to enter AT command mode), then your bt module would not be able to accept incoming pair requests etc.

hope this has helped. :)

  • Thank you for your reply. I think the app may be 4.0. My understanding is the app is supposed to automatically connect. You are not to manually pair it. I can connect to it through my Android Bluetooth settings and also through the Bluetooth Terminal app. So if the app requires 4.0 would which module would you recommend? Thanks again. Feb 22, 2019 at 14:27
  • HM10 would be my recommendation, but there are loads of what look like AT09 (also v4.0) claiming to be HM10's on ebay/amazon. I havent had issues with my AT09 (as of yet, not done much with it, and i ordered more hc05's as the antenna on the AT09 seemed very thin) I'm sure there are android apps that allow you to scan for bluetooth devices using either 'classic' or v4+. haven't tried any of those out myself though.
    – Dekita RPG
    Feb 22, 2019 at 14:36
  • Thank you. I will get an HM10 and try it. Feb 22, 2019 at 14:57

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