FOCBOX + HM-10 Bluetooth do I need resistors?

Having looked through a few threads I noticed a couple of posts recommending using resistors on the RX pin of the HC-05 :

Do I need to use these resistors on the HM-10 I have? The RX/TX is marked as being 3.3V

or can I just connect like this?:

You don’t need the resistor, but you need two cross the RX and TX as @Ackmaniac explain.


thanks for the info :slight_smile:

Thank you for this!

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Umm, not sure about this. Two resistors act as a voltage divider to bring the 5V VESC/FOCBOX TX (transmit) pin down to 3.3V Bluetooth module RX (receive) pin. And you basically said that you have module marked as being 3.3V TTL. I think you do need resistors. It will (probably) work as is but it might also burnout (sooner or later).

Also, both diagrams are wrong. First one is using voltage divider for TX->RX and yet it connects to 5V VCC which makes no sense. There is nothing basically incorrect with second diagram but it is wrong for your usage (with voltage divider resistors). If you are going to use resistors, you do not connect last 5V pin but second to last 3.3V one. Keep in mind that image is showing VESC and not FOCBOX that has this plug rotated 180 degrees. Pinout is the same but rotated.

I went with what @JohnnyMeduse said and connected without the resistor(s).

It’s been working flawlessly since I connected it.

As I said, it will probably work but for how long.

TLDR, if I had Bluetooth module rated for 3.3V, I would use 3.3V to power and send data to it and not 5V. Makes sense, no? :slight_smile:

If you prefer there is a 3,3v pin on the vesc

I know, see post above.

Sorry my bad … :sweat_smile:

I’ve just got 10 pairs of JST 2.0mm 7-Pin PH Housing Female Connector with Wire and Male Connectors if anybody in the uk needs one and willing to cover postage.

I’m just about to solder my HM-10 cable up.
There still doesn’t appear to be a consensus on to use the resistors or not. My HM-10 looks to be a cheap Chinese knock off without the crystal. Does this make a difference.
I’m also using the Hobby King Turnigy SK8-ESC.
Also my VESC enclosure is aluminium will I have to make a slot and expose the PCB antenna to get reception. Thanks.

been using mine for about a year without the resistor and no issues

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I have Firmware 3.52 and I connected a hc-05 I can connect to Bluetooth on the app but no values are showing.

I also added the resistors on Bluetooth rx

Update: I can connect using Windows laptop to Bluetooth com and configure using vesc tool. Works well and also shows real-time data.

Just the app cannot read values…

Did you approve read/write or what it’s called in english. App permission might be a better word

I just have storage permission option. If I check permission details I see also permissions about Bluetooth but this ones there is no option to enable or disable.

I am running android 9 p20 pro