Issue with HC05 Bluetooth Module Communication When Using External Battery

[Minaihab]

I have a problem in my project involving the STM32L010RB MCU and the HC05 Bluetooth module.

Currently, the system operates smoothly when connected to the USB port. The HC05 Bluetooth module successfully performs its data transmission and reception tasks without any hitches. However, upon introducing an external battery and jumpering pins 2 and 3 on JP5 to provide the Bluetooth module with a 5-volt supply, the module appears to power up correctly, as indicated by the LED, but fails to transmit or receive any data.

I have thoroughly reviewed the connections and power supply, but I have been unable to identify the root cause of this issue.

[Mike_ST]

Hello

What board is it ?

Is it a custom board or a Nucleo ?

[Minaihab]

Hello,

Board Nucleo-L010RB 

[Andrew Neil]

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@Minaihab wrote:

 STM32L010RB MCU and the HC05 Bluetooth module.

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How are they connected - UART?

Have you looked at what's happening on the (UART?) connecting lines in both the "working" and the "non-working" cases?

What battery are you using?

Show some good, clear photos of your setup; radio transmitters inherently draw large current peaks, so any issues in the power wiring are likely to disrupt things.

Try putting a scope on the module's supply pin - is it good and steady? Again, compare  "working" and the "non-working" cases.

EDIT:

On debugging serial comms:

https://www.avrfreaks.net/s/topic/a5C3l000000UaFXEA0/t153137?comment=P-1212903

[Minaihab]

We used LPUART in our project.
Also we used 2 lithium batteries connected in series each 3.7 volts.

[Andrew Neil]

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@Minaihab wrote:

Also we used 2 lithium batteries connected in series each 3.7 volts.

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What capacity are those batteries?

Again:

• Have you looked at what's happening on the UART connecting lines in both the "working" and the "non-working" cases?
• Show some good, clear photos of your setup;
• Try putting a scope on the module's supply pin - is it good and steady? 

[Minaihab]

Rechargeable Li-ion Battery18650 (3.7v 1200mAh)
I measured the voltage across the module's supply pin, and it was 4.7 volts.

Should I change any other jumper for the data transmitting and receiving using the battery ?
 

[Andrew Neil]

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@Minaihab wrote:

I measured the voltage across the module's supply pin, and it was 4.7 volts.

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That's not what I asked.

You need to look at it with an oscilloscope to see if it is steady.

Your photo shows only the Nucleo board - we need to see how the battery and the HC05 are connected.

Again:

• Have you looked at what's happening on the UART connecting lines in both the "working" and the "non-working" cases?

[Minaihab · Accepted solution]

Hello,

I found the solution to my problem: to start data transmission to or from the Bluetooth module, we should press the reset button on the microcontroller.

However, I have another problem with ADC 2 and ADC 3. One sensor always gives the maximum reading, and the other has no response, while all the other ADCs work. I am using Tim2 and LPUART.

[Andrew Neil]

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@Minaihab wrote:

I found the solution to my problem: 

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Excellent - please mark that as the Solution.

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@Minaihab wrote:

I have another problem 

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Please start a new thread for that. You'll need to include a lot more detail!