Hi all,
A friend's sister has a birthday in a couple of weeks. She is severely autistic and lives in care. I'd like to make a book for her similar to this type of thing but with sounds and pictures of things she knows and loves.
The back of this book (which I own but can't cut it open!) is about 8mm thick and houses all the electronics and switches. When you press on a page, it just presses through to this part at the back. I can make the physical book by hand no problem.
I've got experience using arduinos (megas, unos, nanos) as well as basic soldering and circuit building, but I consider myself an enthusiastic hacker at best. I tend to get things done, but not always based on a full understanding 
I'm wondering what the best - and cheapest - solution for this would be.
After searching, I see things like the ItsyBitsy M4 is a possibility (built-in DAC and 2MB flash memory). Or a Teensy with the Prop module (ideally the LC version without motion detection).
I have lots of Chinese nano clones in the house already. One option is to use one of those with TMRpcm but for that I'd need an sd card adaptor or similar for the sound.
Not sure about the power usage of the Nano though. What matters most is it works, and I get it to her in time, but a close second is that it lasts a fair bit of time before needing to change the batteries. It will only be waking up on button press, playing an audio file, then going back to sleep
This book is powered by 3 x 1.5v LR1130's - I was originally thinking of a CR2032, but 3 x LR1130's is fine, and should obviously make it easier to power properly.
So I need something small, thin, with a DAC, that is low-powered and able to go into a very low-power sleep mode. Would prefer something cheap too, as going to have to put a lot of work into this quickly to get it done in time and rather not add too much cost to it!
The Paco book has 16 switches, not totally sure I need that many (it has 2 per page - a sound effect, and a snippet of music).
I have a standard 16 switch membrane matrix keypad unused, this type - https://www.amazon.es/Teclado-Interruptor-Membrana-Teclas-Arduino/dp/B018CGKAYY/ref=asc_df_B018CGKAYY/?tag=googshopes-21&linkCode=df0&hvadid=170884034566&hvpos=&hvnetw=g&hvrand=3020778342194840411&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9047063&hvtargid=pla-219554677732&psc=1
I can't use it as it is though, they are too close together and if she pressed in the wrong place sightly and got a different sound, it could really upset her.
Is there anyway to cut these up and move them around? Or is there a good, low-cost, alternative so I can have the buttons spaced out more?
So another nice-to-have would be enough pins to run the matrix - otherwise I can use resistors to run it off one.
Finally, any suggestions on a half-decent thin speaker driver? Again, quality doesn't have to be amazing obviously, just good enough so she can hear it.
Thank in advance for any help you can give!