[Soekris] Error LED Control from Linux userland?
smead at amplepower.com
Tue Apr 16 16:43:02 UTC 2002
I should have made this suggestion earlier, but perhaps it's not too late.
In our own products we use two LEDs to convey information to the user.
The green one provides status and the red one describes an error.
Information is provided by the on/off times of each LED, and is based on
seconds which users can count easily, (and report to our tech support
staff). Constantly on is a `message', but it could mean the processor is
locked up, so probably should be avoided. The most obvious pattern is one
second on and one second off, (1-1), which suggest it be used to signal
There are lots of combinations, but spreading the times works best for the
user. That is, they can interpret 1 on, 1 off, or x on x off, but 2-3
may get confused with 3-3. So if you need lots of codes, you need to have
spread codes like 1-6 or 6-1. 2-4 and 4-2 work, but the longer any one
time, the greater the spread should be to it's pair.
Detecting status and errors and reporting them in a user readable way was
the best thing we ever did to reduce tech support calls and time spent
How many lines and characters are you looking for? The Soekris box is
very small, and finding an LCD that fits in it will be a trick.
On 16 Apr 2002, John Laur wrote:
> On Mon, 2002-04-15 at 17:17, John Laur wrote:
> > In the future, I'll probably add a couple flashing modes with different
> > delays so that you can indicate several states with this led easily. If
> > I need it for my app, I might add blink patterns as well since the
> > net4501 has no speaker. (might not be a bad idea for ComBIOS :)
> Sorry to keep replying to myself on this list, but to those of you who
> requested it in private mails, I uploaded version 1.1 of this driver
> which allows you to set the error LED into blinking states as well as
> simply on and off. You can set it to 0 (off), 1 (on), and from 2(1s
> blink rate) to 9(extremely agitated). Reading the value will indicate
> which blink state it is in also.
> Get it here:
> With regard to Soren's earlier post, the errorled driver no longer
> requires the MMCR to be aliased (it checks for aliasing and works
> accordingly then, too), but if it's not aliased you lose the ability to
> talk to the LED or other gpio's from userland. The mmcr_alias driver is
> still around to make the sc520_wdt watchdog driver happy, though in case
> you want to access your GPIO's from userspace for whatever reason.
> My next task will be finding a cheap parallel LCD panel to hook up to
> the GPIO pins. (parallel panels being much cheaper of course than the
> serial variety) CrystalFontz has some good looking inexpensive panels
> but they look to be slightly too tall (on the PCB side) to mount inside
> the chassis facing forwards. Does anyone know a source for slimmer
> displays that would fit inside the unit?
> Share and Enjoy,
> Soekris Engineering, technical discussion mailing list
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