1st: sorry for the initial empty post, I hit enter all too soon :-)
I am about to add an amp100 based subwoofer to my beocreate 4 (bc4) based speakers. In order to keep the females in our hosehold cool, I'd like to avoid the famous infamous pos at powerup. For the bc4's I added a dsp project file and a timer relais. Works like a charm - for all bc4 based stuff.
On to the amp100: I read the docs, namely in "https://www.hifiberry.com/docs/hardware/gpio-usage-of-hifiberry-boards/", section on amp100:
GPIO4 is used to control the MUTE function of the power stage. Pulling it to high will mute the output
"GPIO4": Raspis GPIO4 or what else?
Further: "Pulling it to high...":
- What level? 3.3V, 5V or VIN?
- I guess there should be a pullup resistor to keep currents low, correct?
- What value?
- If muting occurs on "high" level, what happens at power up:
popping noise will occur?
- On the bc4 I hat to simple add a normally close timer to the mute jumper. That looked to me to an easy, well pre-thought solution. Is this really the same on the amp100?
This pinwas never designed to be used fromoutside. Yes, it's GPIO4 from the Pi and you have to pull it to 3.3V. Otherwise you will damage your Pi.
I would use something like 50-100kOhm.
The state of the Pi's GPIOs on boot depends on all kinds of configurations. Usually GPIOs are configured as an input which makes the state undefined.