Stupid stuff about RPI

Thoughts & Feedback
#1

DO note before reading, I never owned one of these things, of any revision. I am just working off of prior knowledge elsewhere, hardware already available and an idea on how I’d like to build a cheap PC, and whether or not it could be feasible.

I want this thing to have an optical drive and hard disk. So using the RPI3B as a base, and assuming my hardware is intended for laptops, without going into details on how in my head I want to mount this stuff I want the data and power to be done as easily as possible. The easiest way I can think of is as such;

SATAd -> USB
SATAp -> LP4 / Molex

Using the power demands from the ModMyPi website, they claim all you need is 5V@2A to run the Pi. Whether this is true for the 3B is something I am unaware of, but i am assuming this for the hell of it. It still needs power, and 5V@2A is easy to come across yeah? Every power brick for LP4 has both a 12V and 5V rail with 2A. So then I wonder;

If I were to chop a USB B Micro dedicated charge cable and crimp on (or solder in) some pins and shoved the ends into an LP4 housing, could I then power the hard disk, optical drive and Pi itself using a 1-to-3 LP4 adapter with the receiving end outside of the case?

The thing has a CSI so I could add in a camera which works with the B3’s interface and have that somewhere, or I could just run it from USB by having a USB pass-through on the outside of the case, or separately -powered USB hub if I wanted more equipment. Wireless could be handled by a USB-connected Tx / Rx and the media devices could be plugged in via USB by a SATA to USB adapter.

I read earlier that you can boot from USB with some tinkering about, so would it be possible to use a 256KB microSD and use that to put the bootloader on, which could then be used to boot off the hard disk?

Would it be too much for some cheap LP4 power adapter to handle? Would I need additional components? I already know I would need to extend the HDMI connector to whatever case I shove it in for video. I’m just poking here so don’t bite back too hard, please.

#2

I’m going to go out on a limb here: Wouldn’t it make a lot more sense to just get some external device enclosures and call it good? You can get the devices in OOB fashion, or obtain bare devices and put them into one or more enclosures.

Definitely connect them via a powered USB hub attached to the PI if you’re going the former route. If you go the latter, so long as the enclosure(s) get power externally (i.e. not via the USB port), you shouldn’t have to worry about taxing the Pi, hub or no hub.

Mounting should happen automagically when you connect the device(s)…

#3

I know the justification for such a setup is a little weird, but I was talking about making a mini-desktop from a Pi, with a power supply from mains that isn’t just for USB.

Using external enclosures means I still need to rely on USB power and from my experience an optical drive from a laptop might just do, but such a thing really works better with external power not from the host machine.

#4

If I understand you correctly, not necessarily. You can get external enclosures that have their own independent power supply. It’s not the only one, but take this 5.25/3.5 enclosure on Amazon (link) as an example. Enclosures of this type, capable of holding multiple units also exist…

#5

It sounds like you’re trying to build a mini desktop PC using the Pi?

#7

My power supply, being one of those things you’d see on (better) data recovery kits can run two devices just fine, so I don’t think the inclusion of a Pi would cause it much issue. I was just writing about this to make sure.

I’ve tried before with two hard disks, one disk and an optical drive, a hard disk and a smaller board which needed external power to convert IDE to SATA data, etc. and it’s alright.

How are you powering the Pi? Via MicroUSB or GPIO?