Is HM-10 RX pin receiving data to be transmitted?

[Pommie]

I've managed to get myself very confused. The HM-10 (BLE module) has a RX and a TX pin that get connected to an Arduino as follows (I think),

The TX pin of the Arduino sends out the serial data and connects to the RX pin of the module - blue wire.
So, is the RX pin of the module accepting data to be transmitted?
In other words, is the above diagram correct?

Thanks,

Mike.

 

[Papabravo]

Unfortunately, a fritzing diagram is about as useful as a screen door on a submarine. If I were to make book I would swap the connections, you are showing.

 

[sagor1]

Not sure of your model, but many of the HM-10 are 3.3V devices, not 5V. Now, your board may have level converters on it, can't tell by your pictorial. Check the datasheet for your device. Otherwise, the TX/RX connections should be correct if labelled properly on the HM-10 board.

 

[Pommie]

My module is indeed 3.3V but I'm using a resistive divider from the Pic TX pin to the modules RX pin. I believe the Pic's RX pin "should" work fine on 3.3V. I'll meter the model when I get it to ensure the RX pin etc. is correctly labeled. Not really got room on my PCB to add level converters.

Mike.

 

[Pommie]

just found this image. It is of the bare module rather than one mounted on a PCB so it depends how the PCB is connected. Looks like metering it might be the only way.

I'll post my findings when I have them.

Mike.

 

[For The Popcorn]

Normally Rx --> Tx and Tx --> Rx, but some devices, trying to be helpful, label the pins as what they should connect to rather than what they are. So NOT helpful!

Transmit pins should output a high signal when idle; receive pins will be low at idle. Check with a meter to verify which is which.

 

[For The Popcorn]

I used to have a book on serial interfacing. The most useful thing in that book was: "ignore the documentation Chances are, it's wrong."

 

[rjenkinsgb]

The TX pin of the Arduino sends out the serial data and connects to the RX pin of the module - blue wire.
So, is the RX pin of the module accepting data to be transmitted?
In other words, is the above diagram correct?

Correct in principle, TX and RX are relative to each module they are on, in that case.

However, remember that the HM-10 operates at 3.3V internally, you need a resistive divider if the MCU TX signal is 5V.

 

[Pommie]

It seems especially confusing with a Bluetooth module when data into the RX pin might cause the data to be transmitter over Bluetooth, hence both directions. Think a meter is the only answer.

Thanks all,

Mike.

 

[Papabravo]

A schematic diagram of EITHER board would be most helpful. It amazes me that they are so rare.

 

[Les Jones]

Here is a link to the datasheet for the HM-10. It indicates that TX should be connected to TX and RX to RX.

Les

 

[For The Popcorn]

So helpful when they try to make it easy by avoiding convention!

There's something to be said for labeling like this:

Tx>

Rx<

 

[rjenkinsgb]

Here is a link to the datasheet for the HM-10. It indicates that TX should be connected to TX and RX to RX.

That's an adapter I believe; the signal names are the same, just extended.

This one explicitly shows the interconnection is TX>RX and RX<TX - page 6.

https://engineering.fresnostate.edu/research/bulldogmote/documents/11.%20HM10%20BLE_FTDI.pdf

 

[Pommie]

If they had a description of what the pin does it would be helpful.
I "think" the RX pin is,
"Recieves data from the attached device for transmission over bluetooth"
So the RX pin may be the transmit data pin!!!
No wonder I'm confused.
As stated, I'll check which pin is held low when I receive the modules.

This one explicitly shows the interconnection is TX>RX and RX<TX - page 6.

As I showed above (#1 & #5) both are shown on the internet. It's just that noone seems to know which is correct.
I suspect that if it's a module (on PCB) it's RX>TX etc.
But if just a chip (none mounted module) it's RX>RX etc.

I'll post a definitive answer here in a few days.

Mike.

 

[Nigel Goodwin]

If they had a description of what the pin does it would be helpful.
I "think" the RX pin is,
"Recieves data from the attached device for transmission over bluetooth"
So the RX pin may be the transmit data pin!!!
No wonder I'm confused.
As stated, I'll check which pin is held low when I receive the modules.

It's seems fairly random on the Chinese modules, it's something you always need to check and make sure - I'm sure pretty well all of us have fallen foul of it at various times