[nSLUG] Powering a RPi (was Re: Cellular dongles)

Dave Flogeras dflogeras2 at gmail.com
Mon May 27 14:30:15 ADT 2019

On Mon, May 27, 2019 at 1:44 PM Joel Maxuel <j.maxuel at gmail.com> wrote:

>  Interestingly enough, I discovered one of those conclusions earlier today
> with the MoPi2 (paired with the stacking header):
> https://pi.gate.ac.uk/pages/mopi.html
> ...which will allow up to 2.5A (given if each peripheral peaks at the same
> time - that can still leave 960mA) for the Pi.

That's the one I couldn't remember earlier!  Make sure you read up on any
candidates, there is always a varying degree of quality/support.  Some of
these products are just pet projects, with no intention of doing proper
software/kernel level support after it is released.  YMMV.  IIRC I
evaluated a Pimoroni E-Paper board, and while it did do what it said it
would, it wasn't integrated in any way to the operating system; just some
hacks and python scripts to communicate with it.  Same went for the early
Wolfson audio boards, unsupported bash nonsense and user daemons in lieu of
a proper driver (which the community has since created).

>> And this way you could position your board between the pi and Razberry2.
>> You could break out the supply pins, and any other peripherals for any
>> customization you need (UART, I2C for realtime clock....).  It's pretty
>> cheap to get PCBs made up at OSHPark and if you have a couple random
>> circuits, it can greatly clean up your project.  When you're getting
>> closer, I'd be happy to show you enough KiCad to make you dangerous.
> Not sure how important that detail will be, as the finished product will
> be in my basement (likely mounted to the wall in a panel box).  You
> mentioned breakout for an RTC - is internal time-keeping that bad, or just
> plain non-existent?
The Pis don't include an RTC, probably to save a bit of BOM cost/real
estate of having a coin cell on board.  It's easy enough to add one; I've
spit rolled my own but I would imagine kits are readily available by now.
Most people don't care, since typically they are always connected to get
NTPD to update the clock.  In my experience, the internal clock doesn't
skew more than your average PC.


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