I am using the DY-HV20T MP3 player in its simple MP3 mode. I do not use serial communication with it, only the IO-0 and IO-1 inputs to control the volume and play the previous/next file. This has worked fine by using a small reed relay to ground those inputs when needed. But now I'd like to do away with the relays and use logic outputs from a Pro Micro board. My question: Is it ok to apply 5V on IO-0 and IO-1 of the DY-HV20T, then apply 0V to ground those inputs?
No.
The buttons in the drawings are grounding the pins. The pins are probably "held high" with nearby components.
Yes, you are right. There appear to be internal pull-up resistors on those inputs on the MP3 player.
To confirm that, I measured 3.3V on them.
I think I found a solution. A website called Digital Town (UK) suggests using a voltage divider between the Pro Micro 5V output and the MP3 3.3V input.
I wired this up and it works perfectly. To go one step better, I will order some Bi-directional Logic Level Converters (5V to 3.3V)
Thanks for leading me in the right direction.
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