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Re: Selecting compatible Raspberry Pi components



On 05/03/2020 02:23 PM, Jeffrey Walton wrote:
On Sun, May 3, 2020 at 12:59 PM Richard Owlett <rowlett@cloud85.net> wrote:

I've been thinking about what a handheld computer COULD be.
My image is heavily influenced by my recollection of Palm Pilot.

My project goals are two-fold
    1. create a personal data logger reminiscent of a Palm Pilot
    2. become familiar with Raspberry Pi while using Debian as the OS

My needs include:
   >2 hours battery life
   4" by 7" nominal form factor
   touch screen input using a stylus
   display will be entirely character mode (40 chars/line would be OK)
   OS GUI not required except to say where stylus is
   OS shall be Debian {possibly with non-free drivers}

I've not found found user friendly selection guides.
A typical problem was not being able to know if a selection of
components had mutually compatible I/O (electrical and physical).

I can't speak for others, but I once I select the RPI (usually a RPI3
or RPI4), head over to Amazon and look for the accessories. Cases are
$10 to $30 USD, screens are $20 to $50 USD, etc. I've never shopped
for a battery so I can't really say anything about them.

The only tricky thing I have encountered is screens. If you want to
keep the GPIO pins available for other work, like signals for buttons,
then you need SPI data connection for the LCD screen. The problem is,
SPI connectors are only available for 7" screens or above, which are
usually larger than I need.

The page [1] for Adafruit's 3.5" display seems to say it can use either the GPIO connector or SPI. Determining which display worked with which Pi was a sticking point when I pursued this last year.
[1] https://www.adafruit.com/product/2441

You might also have some trouble with a case. Most cases have openings
for ports but not much more. If you are having trouble finding a case,
then buy one of those inexpensive 3D printers and make your own.

Jeff





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