linux-kernel - Re: Linux support for a 7 segment LED display

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Message-ID: <CAMuHMdX0CYWGn8OSQ3sXGyZTSqjTK5n1aj2-BOudfEejp980Tg@mail.gmail.com>
Date: Fri, 23 Feb 2024 14:01:32 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: Chris Packham <Chris.Packham@...iedtelesis.co.nz>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Pavel Machek <pavel@....cz>, 
	"lee@...nel.org" <lee@...nel.org>, "linux-leds@...r.kernel.org" <linux-leds@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Linux support for a 7 segment LED display

Hi Andy,

On Fri, Feb 23, 2024 at 1:36 PM Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Fri, Feb 23, 2024 at 9:52 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > Note that most larger displays are not individual LEDs, but matrices
> > of LEDs. Do we want to drive/scan them from software, using a
> > gpio-7seg-matrix driver?
>
> LED matrices are the displays (like tinyDRM is for).

TinyDRM is for rectangular matrices.

Multiple 7-segment displays are usually multiplexed using a matrix,
using 7 (or 8) lines shared by the corresponding segments of all
displays, and one common line per display.
https://embedded-lab.com/blog/wp-content/uploads/2011/03/Lab11_Circuit_SevenSegmentMultiplexing.jpg

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds