Well that's because for the Pi you have GPIO. If you just want to run homelabs or software only stuff, why not go for ITX motherboard with just in time components

ITX motherboards also have GPIOs on them by the way, but they're not brought out to header pins like on the Pi.

Thats a great read. I explored similar things with my rooted phone. Samsung galaxy m30s. Wrote something on it as well on what I did, may be you will also like this type of experimentation?

https://nimitbhardwaj.github.io/posts/hermes-agent-rooted-an...

I guess in general, the development experience on a Pi is much better, because it’s made to be tinkered with, right? In the other hand, Android phones are also nicely hackable. I’d just guess that for beginners, it’s much easier to install the Raspberry IDE and plug in the Pi (as opposed to learning how to connect and develop for an Android phone). But yeah, for pros or vibe coders, an Android phone might be the right or even better choice. And it’s great that Android phones can therefore be used a little longer before landing in a landfill.

This is the main issue:

> The open question is supply. Finding two good used phones is easy; finding a few hundred matching ones, with healthy batteries and predictable camera behaviour, would take more work. I feel increasingly confident that it’s possible.

RaspberryPies and such are commodity hardware. You can buy one, two, ten, twenty, a hundred, and it just scales along. All of those devices will, barring perhaps a few dead-on-arrival ones covered under warranty, just work out of the box.

A used smartphone will have issues which can vary from device to device, so scaling that would take a very dedicated refurbishing setup where the quirks are ironed out (and the unsalvageable ones discarded).

I would also expect that you are starting out at the other end of the bathtub curve: with new devices you will have a few that fail soon after unboxing and using them a bit, and then they will run fine for years until you start hitting the other end of the curve and wear-related faults pop up. With old cheap phones you would start out at that side of the curve, so if you buy one hundred of those, a bunch will fail at various points soon after deploying them.

The cost of that unpredictable behaviour seems high to me. So much so that I wonder if it wouldn't be cheaper to buy a lot of unsold stock of a certain type of budget smartphone from two or three years back. Those devices could run fine as long as they aren't connected to the internet directly.

for applications like that your should remove the battery and put small cheap circuit that emulates it. then you can run such server very very safe, unlike with 100x batteries always harging.

Bot farms works that way.

Phones are pretty robust though, meant to handle everyday use and abuse. In terms of failure, the battery is really the only thing to be concerned about. Most phones have some battery limiting option, and bypass the battery when the charger is connected. And if you're determined enough you can run without a battery.

Just plug all the battery slots in parallel to a 4.1V power source (that's a nearly full battery voltage). You probably have to solder them to make a reliable connection.

I'm pretty sure the third/fourth pins are used for communication to the battery. I doubt the phone would be happy it wasn't responding. I vaguely remember some phones can just use a resistor for that pin? Either way it's not quite that simple.

The main issue with old phones are NAND Flash degradation and battery problems. As long as you fix those two issues everything else is simple. These days with AI it's almost trivial to build and flags your own ROM and even the most hardcore of binary blob drivers can be reversed so long you have enough GPUs.

Hobbyist don't usually need to scale beyond one device. Warranty is not that a big issue, if you buy a used hardware you know what are getting into, that's why they are cheaper than new devices.

> RaspberryPies and such are commodity hardware. You can buy one, two, ten, twenty, a hundred, and it just scales along.

Not my experience at all. Pies are hard to find, get more expensive each week. Some are impossible to find (Pi zero).

The most fragile part of a phone is the screen. If you don't care about breaking it, then access to the battery becomes pretty easy, and therefore easy to replace.

You could go a step further and just buy low-end new phones. They are available at sub-$50, which is near the price of Raspberries.

I too have a bunch of cheap android phones of diverse vintage lying around.

Some are bought with US carrier locks - never activated or unlocked. Any chance they can be unlocked with today's tools and not dumped into ewaste.

There are a few simple projects for home automation i have in mind but the rooting felt like a daunting task.

For home automation, just build an app that does what your need. No big reason to root it.

> Why get an expensive Pi when I have an old phone?

Because the pi has a maintained kernel and a userspace I don't have to fight.

Yeah like its a weird article idea where the pi is expensive compared to an old phone which you have for free. But that doesn't make the used phone cheaper. You can just as well say why use an expensive PI when I have an old computer with a 1680ti and 12 gigs of ram. Like yeah okay but what does that have to do with Pi? Entirely different device classes imo

Or what about an old Pi?

Why get an expensive Pi when I have an old free Pi? My issue is with the expensive qualifier. Anything is expensive compared to something you have lying around for free.

If you want to compare the expensive factor, at least use some kind of cost to compare like the price of a used phone etc or the cost of a basic server to see how they differ.

As someone who's tinkered with flashing linux into tablets I can 100% vouch for this. Fun to tinker with. A nightmare to use for real

Is there a peripheral you can plug into the USB port that exposes gpio pins?

Any dev board like Arduino can work. E.g. by flashing firmware that controls GPIO via Serial.

Yes, USB to GPIO adapters are available. Note that you won't be able to implement anything that has timing requirements - you'll need a microcontroller for that.

I think in practice the timing jitter and the low cost difference to something like an Arduino Nano or Pi Pico means people use one of those even if they could technically use a GPIO adapter.

Look at the FT232H. Does SPI, I²C, UART, JTAG, and GPIO. It’s just a chip but there are hobbyist breakout boards for it.

Because big tech decides what you are allowed to run on your phones

A Pi is the Apple of small compute. It's the in thing, flashy, with loads of just as capable competitors.

No one cares if you have overpriced white earbuds or not for Pi tasks.

Everything including compete is priced sky high these days.

And some higher than that, like the Pi, which has been overpriced for years.

Rooting or flashing a modern phone is pain in the ass. Ideally the battery needs to be replaced with a 3.7V PSU (and BMS must be salvaged without cutting the battery accidentally). And for old phones it either old linux kernel, partially unsupported hardware or fork maintained by handful of hackers for free.

I guess laptops are way easier: more upgradeable and repairable, don't require unlocking mostly, battery can just be thrown away and it works with its native PSU. Just need to make sure power won't go out. And it is bulkier, though maybe less susceptible to overheating.

Locked bootloaders mostly

Reasons to get a Pi: GPIO support, software support, OS updates, free root & bootloader, more flexibility and customizability, extensive documentation and support, consistency, simplicity, more ports, battery optional.

Used phones are good for tinkering, especially for "display with sensors and battery attached" usecases, but there are still plenty of downsides. And unfortunately Linux on phones is just not ready for primetime, last I checked.

Your phone has GPIOs inside it, but you can't access them without at least root.

Cool, didn't know that. But like are they physically accessible? I don't think you can use the USB port as GPIO. Maybe some unused pins on the SOC itself, but that means opening up the phone and probably removing the shielding/heatsink...

You can attach some photodiodes to your screen to control things. And use the camera/mic for input.

Now that's a funny idea. But it's true!

I've never used one but android phones can use utilize USB GPIO devices which are very cheap

PI was a thing when it was much cheaper than X86. You can buy a much better speced mini PC nowadays

For the cost of a Pico or a Zero? Even some of the SBCs cost about £30. Where can I get a mini PC for that?

ebay :-)

https://www.ebay.com/itm/147663241534

I'll bite. Wyse 3040. $20-40 on the used market, similarly crappy specs to a Zero.

https://www.parkytowers.me.uk/thin/wyse/3040/

The main reason is that they are one of the few ARM computers sold with a pre-installed officially supported GNU/Linux distribution, at affordable prices.

Even with the prices increases that the PI has suffered, there no systems of vendors like Tuxedo, or System 76, at similar price point, with ARM support.

As long as it's not an iPhone. Once Apple has bricked your old iPhone, you can't even run your own software on it anymore. Despite all their lip service to being environmentally friendly, that thing is nothing but an expensive paperweight and e-waste now.

I also keep using old android phone but the battery dies every few months if you keep plug-in power cable.

You could consider getting an older flagship phone perhaps 2022-2023 and have a strong portable device with a decent amount of compute power and not to mention ram. I'm starting to believe that these devices are under utilised and we will see some interesting applications using either with AI or without.

I particuarly think the economics of this are interesting, if you take the one plus 11 you can get one for around £200-250. The CPU is very capable and the alternatives are a PI 5 or N100. You get 16b of ram, a screen, gps, bluetooth a camera... the list goes on.

These devices could really shine as edge computing devices and I believe they are overlooked.

It does have the same problem as using a laptop as a server: the battery will fail. But it's a nice UPS until then.

A lot more mobile devices will require removable batteries after 2027 due to EU regs.

There are exceptions, so not all phones will, but more will. I hope there'll be more time/effort put into hacking removable battery phones to accept hardwiring a PSU onto the battery terminals over the next 5 years.

The problem with modern smartphones is that they run on battery, even when plugged into external power. You cannot use it without the batteries without some more hardware hacks. As the batteries aren't designed to be always in a fully charged state, if you decide to use the phone with the battery you have to carefully monitor the batteries too if you keep it powered 24x7. Old batteries can also bulge or, worst case, even explode. Another thing you need to consider is cooling - Smartphones are designed with the idea that their CPUs won't run at 100% always. A smartphones CPU, Camera, battery etc. tends to get hot on prolonged use, so if you are, for example, planning to use it as a mini webserver or as a 24x7 streaming cam, you need ensure it remains adequately cool. And ofcourse, the best smartphones for these kind of projects is one capable of running Linux.

Some OnePlus devices have a "bypass charging" system. My OP8 Pro is running since 2y now as a Kubernetes node, and nothing bad has happened to its battery (yet).

I'm honestly curious to see if bypass charging is on, but it's been a while since I touched the device itself and it has been fine do far. YMMV

See: https://blog.denv.it/posts/pmos-k3s-cluster/

Wouldn't setting the charge limit to a really low ceiling suffice?

>>The problem with modern smartphones is that they run on battery, even when plugged into external power.

That's not universally true - a lot of android phones have a "bypass charging" mode where you run directly from the power supply, and indeed you can run them with the battery removed.

Why get an expensive Pi when you can get a cheap 1L PC / tini-mini-micro or SFF pc? Especially if you don't need GPIO pins?

My blog article about this: https://louwrentius.com/the-raspberry-pi-5-is-no-match-for-a...

On a similar note, old smartphones (depending how old of course) are way more powerful than a Raspberry Pi. You can turn them into a Kubernetes cluster [1].

[1]: https://blog.denv.it/posts/pmos-k3s-cluster/

I recently used Termux on a 7 year old low-end android to run a WordPress site with sqlite db and a golang sse pubsub service at a conference, via cloudflare tunnel, with dozens of people connected and doing some realtime collaborative stuff. Worked perfectly.

It was vastly more powerful than the old RPi 3 that i have, and significantly easier to work with given the screen, keyboard, wifi etc...

For me if I don't have a need for the GPIO pins, it's "why get an expensive pi when I can get a used ex-corporate small form factor quad core, intel core i7-something desktop PC with 16GB of RAM and a real SSD"... For like 150 bucks on eBay. RAM apocalypse and price of equipment has affected this a lot (these used to be like 90 bucks depending on era of core i7), but they're vastly more useful when a general purpose x86-64 linux is installed on them. Or even just put proxmox on it and then various things inside that.

What about GPIO support and Raspberry Pi OS updates?

>Why get an expensive Pi when I have an old phone?

>I’ve unlocked and rooted the Redmi

Herein lies the issue. I don't know fuck all about phones. I don't want to. They are engineered to keep me out, and that is a pain in the ass I don't want to deal with when doing hardware work. I want to own something that works the second I get it and doesn't fight me the entire way. Sure, I could let an LLM guide me through it or even do it for me, but why bother when the whole point of the hardware is for me to fuck off and use it as a subscriber to the OEM and carrier? This is tedium, removed by further spending. Not to mention documentation - what bullshit is the OEM hiding in their board or firmware thats going to ruin my day? I'm sure that some of these devices are great for reuse as a self contained server with media and modem, but _is my old phone going to do this?_

I'm not gonna spend $50 on ewaste to _try_ to do something unless I _want_ to use _that_ ewaste (old keyboards, old toys? :3). Old phones are a non-sequitur because, again, they're engineered to keep me out.

>>Herein lies the issue. I don't know fuck all about phones. I don't want to. They are engineered to keep me out, and that is a pain in the ass I don't want to deal with when doing hardware work.

I mean, you do know we're on a forum called hacker news, right?

In most cases it's not some magic voodoo process that you need an LLM for, it's the first result on Google and one command to run or in some cases you just hold two buttons together when booting up and click the unlock button.

Like, I completely understand your perspective and desire to have things which "just work"(I'm in the same boat a lot of the time lately) but like, let's be realistic - rooting an old phone and running some software on it is really not a big deal, I'd hope especially for people on here.

I have recently taken to gathering old phones and putting Nerves on them (Nerves packages up the Erlang VM into a mainline kernel to run on a variety of devices). I got inspired by a talk by Marc Lainez at Goatmire who had put it on a variety of exotic devices (e.g., a Wii).

I am by no means an expert at this, but starting of with a device on the Postmarket OS list and Claude, you can get a lot of these old devices working with mainline Linux and nearly all drivers. The newer devices are a bit harder, but if you go back nearly a decade, they're very easy to get working.

So far I have repurposed a Fairphone 3, Nexus 5, Galaxy S20, and Galaxy Tab 3.0 7". All of them (except the s20) with all drivers working compared to stock. Others have done a lot too: https://github.com/mlainez/awesome-nerves-systems

For DIY projects you can use host USB, or get one of the Adafruit FT232H type boards for GPIO pins.