This circuit I am using to drive a speaker is acting strangely.
Case 1: When I connect the 3.3 volts source from the Nucleo board it works fine as expected (in terms of the sound.) When I check the voltage across source it is 3.1 to 3 volts. A drop of only .2 to .3 volts.
Case 2: When I connect the GPIO output pin 3.2 volts as a source to the circuit, the speaker sounds very low. When I check the voltage at the GPIO pin it is 2.1 to 2 volts. It drops nearly 1 volt.
Why is it dropping so much voltage? Due to this speaker does not sound as expected.
What is the issue? Can I resolve this?
Edit: The GPIO is from a BlueNRG-1 chip.
Best Answer
You need to do something like this:
simulate this circuit – Schematic created using CircuitLab
That delivers power to the speaker as needed, but allows you to turn on the BT66 (which seems to be an FM radio receiver) with the signal from your GPIO pin.
As has already been noted, IO pins from microprocessors aren't intended to provide power. They are control or data signals, and cannot provide high current.
The above sketch assumes that the BT66 is powered from something appropriate. You didn't show the power connections for it in your sketches, and I didn't make an effort to find a datasheet or other description of it.