Noise from speaker on qwiic MP3 trigger when also using qwiic alphanumeric display

Qwiic System
1

I seem to be having some interference from an alphanumeric display when playing mp3 files with the mp3 trigger.

Setup:

Redboard qwiic (DEV-15123) power via usb connection to computer

Qwiic real time clock module (BOB-16281), INT connected to D2 on redboard

Qwiic Alphanumeric Display (SPX-16427)

Qwiic mp3 trigger (DEV-15165) connected to speaker (COM-09151)

Whenever I play anything on the mp3 trigger (via mp1.playFile()) I hear a buzzing sound coming from the speaker along with the mp3. It I remove the alphanumeric display, I no longer hear the buzzing with playing a mp3.

I tried changing the order the qwiic components were connected, adjusting the brightness on the display, and changing how many segments were lit on the display. None of that seem to affect the amount of noise.

If I remove the speaker and use headphone jack I no not hear the buzzing.

Any idea how to resolve this?

2

  • - Are you physically removing the display or just commenting out the display in code?

  • - Have you tried moving the cables at all so that the wires are in a different orientation to the board? (might be a bit of RFI getting into the amp)
    • 3

    I physically disconnected the display.

    Yes, I had tried moving things around: both physically, and the order the qwiic components were connected. Neither seems to have an affect.

    4

    I’m not really sure what might be causing this unfortunately.

    Software wise there isn’t any reason why activity on the bus would be causing noise on the Qwiic MP3 Trigger. The only thing I can think of to try would be to move the components around or change the order they appear on the I2C bus to see if that helps. Keep the display as far away as possible from the MP3 Trigger and if that still won’t work, you might have to use an external amp connected to the headphone socket.

    5

    The display is a multiplexed display, so it is drawing quite a bit of current, and the current changes as each digit get scanned. This could easily bounce the voltage on the qwiic bus, and since the mp3 trigger is also powered from that bus, it could be affected. Long lengths of 28AWG qwiic wires won’t help.

    Two things I would try:

    • Add some bulk capacitance to the display, say 470uF or so

    • Use PRT-14425 and power it from the Arduino directly; this way the mp3 board should get cleaner power

    /mike