How simple is too simple for elderly users? One button or a few?

Built one of these for my mother-in-law two years ago, and I started out on the dead-simple side. One big arcade button, a Pi Zero 2 W, a small speaker in a photo frame I gutted. Photos came thru a Telegram bot, and pressing the button played whatever voice note was attached to the newest picture. No menus, nothing else. I was proud of it and she hated the button, because pressing it felt like a commitment. She wanted to hear a message twice sometimes, or skip past her cousin's ten-minute ramble, and one button could not do either. So the walk-back was adding two more buttons. Replay and skip. That was it, and it fixed nearly everything. The volume I handled differently: I set it once at a level she liked and left it alone. Turning it down for her was a mistake I made early on, she leans close to the speaker and quiet audio just reads as broken to her.

On your cassette point, I think that is the right instinct but the wrong comparison. A cassette recorder had three controls and she could see the tape moving. What confuses people her age is not controls, it is screens that change when you touch them. Physical buttons that each do one visible thing are fine. Give him rewind and volume if they are real switches, but keep every control tied to one action and never let the display show anything but the photo.

One practical thing: mount the buttons slightly off-centre so a knuckle resting on the frame cannot accidentally trigger one. I learned that after she skipped a birthday message and nobody could work out why.

My aunt is 82 and grew up with a hi-fi stack in the lounge, and when I built her something similar on a Pi 3 I deliberately gave her three real controls: a rotary volume knob off an old radio, a big round button for the newest message, and a smaller one that goes back through older photos. She uses all three. The knob gets the most use because her hearing is better on the left ear and she angles it toward her good side, which no software setting would have guessed.

The cassette recorder comparison in the original post is the right instinct. Familiar physical controls are not a burden to that generation, they are a comfort. What actually confused her was anything on a screen. Touchscreens are the enemy, not buttons. My first version had a tiny on-screen prompt and she never once touched it.

The mistake I made was hiding the older messages. For the first month she only ever heard the latest one, and it turned out she had been going back to the kitchen to ask my cousin to resend things she liked. Once the back button existed she spent whole afternoons listening through the archive. So I would say give the rewind and the volume, keep the big button as the obvious default, and skip every menu entirely.

One practical note from the build: mount the speaker facing out of the frame rather than through the back, the difference in volume through a wooden front panel was bigger than I expected.

The hardware side of mine went fine, it was the SD card that nearly sank it. Built a similar frame for my mum and after about eight months the card corrupted and she was staring at a frozen screen for two weeks untill I could get over there. Now I keep a spare card at my house with the exact same image on it, and when anything breaks I post the spare down and she pops the dud back to me. If you are building this for someone 400 miles away, make the spare part of the plan from day one rather than learning it the slow way like I did.

Did mine with a blinking light nicked from an old answering machine, and honestly that little red light did more work than any button. My uncle could ignore the frame all week, but when that light flashed he knew something new had turned up, same as the message light on the phone he'd had since the 90s. No screen needed, just a GPIO pin and a ten-cent LED. Question for the OP: what happens when nobody in the family sends anything for a fortnight? Dead frames kill the whole thing. My fix was scheduling a message from me every Sunday wheather I had anything worth saying or not, keeps the light blinking and keeps him checking.

I'm following this because I want to do the same for my nan, only I keep getting stuck on the boring part, the getting-pictures-in side. My family group chat is full of blurry rubbish and videos of the dog, so someone would have to pick the good ones before they reach the frame. Do you plan to sort them yourself first, or just let everything through and let grandad skip the duds? Also wondering how the little computer inside actually grabs new photos, does it need the wifi password typed in once and then it just keeps checking on its own? I've only ever used one of those boards to blink an LED so the sending part is the bit my head can't picture yet.

Not sold on the set-the-volume-once idea from the first reply. I tried that with my nan and it fell over within a month. Her hearing is not the same every day, some mornings the telly is on in the next room, some days she's tired. What reads as fine on Tuesday is inaudible on Friday, and she never told me, she just stopped pressing the button because she assumed the thing was broken. A knob you can nudge without thinking beats a perfect level nobody can change. Mine is a cheap potentiometer wired inline with the speaker, took ten minutes and saved the whole project.