Wife gave me a new project: create a speech assistant device for our autistic son.
Well, she told me to "get one", and they are around $200 :o
All it has to do is have a series of buttons (matrix keypad expanded, essentially), and play an audio file when he pushes the button relating to a small picture on a pad.
Going to use an "art case" as the case for this, just to get it big enough, so PLENTY of room for stuff, unless somebody has a great idea for an similar sized case for under $20. I could 3D print one, but it would actually be smaller than the art case (albeit I could make it stronger).
Now, how best to run this device?
My first thought was a DFPlayer and bare 328 controller (I keep both in stock), just run both on 3.3v.
The biggest challenge with that setup is how to keep the standby current EXTREMELY low, but wake instantly on a button push on the matrix button scheme (is that even possible?).
From what I've found, in "sleep" mode, the DFPlayer draws some 20ma. Kind of a lot. Thought of using the 328's sleep mode, setup an interrupt on the matrix keypad (if possible...), and then have the 328 turn on the DFPlayer via MOSFET, then play the corresponding mp3 file. But those DFPlayers take about 3-5 seconds to boot up, way too slow.
Then I stumbled across this guide to play wav files: linky
I've never played with the SD card reader OR that audio amp, any experience with how long it would take to get everything going after the matrix button interrupt?
I need the time from button press to audio playing under a second to make something my son might use.
I plan to run this all off of a battery, and I need the battery to last as long as possible. I may rig up an 18650 battery and integrate a charge controller so I can just plug it in at night with a regular USB-C connector, like his other stuff. I'd love to get at least 2-3 days battery life, but if I had to plug in nightly, I could deal with that.
Any thoughts are much appreciated.