In my last log entry I mentioned about the need to mute the amplifier while the unit switched on as you need to give the amp chip about 1/4 second to boot. This meant that the amp would play anything on the input at near full volume until the controller could turn the volume down. The controller doesn't have any IO left to control the mute pin on the amplifier so I needed another way to hold the mute pin low for at least 1/4 second.
I wanted it to be as simple as possible so started with the idea of a simple RC timer to hold the pin low. While this worked, the issue came from the inability to quickly discharge the capacitor once power was removed. This would have meant that if the power was applied before the capacitor has discharged it would start again at full volume. The capacitor does discharge, just painfully slowly!
After a lot of investigation I came to the conclusion that I would have to go a bit more complicated. On that post user Ken Yap said about using a small basic microcontroller to hold the pin low, but that felt a bit of a misuse of a microcontroller, although I did appreciate the suggestion :D
That though made me think, there is a chip that is A) Cheap and B) designed for this exact purpose. The venerable 555 timer!