Power off on the PiZero W


15 posts
by NickT » Thu Mar 16, 2017 9:07 am
I recently bought a Zero W. It works well but I have noticed that when it is powered down the LED does not make the 10 flashes that other Pis do. I did comment on this in another thread which was concerned with the fact that initially the LED didn't light up at all on the W but is now fixed. I'd hoped that a developer from the Foundation might make a comment about the missing flashes but there was none.

When I do power down, the LED does turn off, so is it safe to assume that it is then OK to pull the power lead out once this has happened?
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by noggin » Thu Mar 16, 2017 9:23 am
NickT wrote:I recently bought a Zero W. It works well but I have noticed that when it is powered down the LED does not make the 10 flashes that other Pis do. I did comment on this in another thread which was concerned with the fact that initially the LED didn't light up at all on the W but is now fixed. I'd hoped that a developer from the Foundation might make a comment about the missing flashes but there was none.

When I do power down, the LED does turn off, so is it safe to assume that it is then OK to pull the power lead out once this has happened?


The Pi 3 B doesn't do the 10 flash thing either does it?

I think the Pi Zero W, as it uses the same WiFi+BT solution as the Pi 3B, uses a different GPIO configuration, and the LEDs are no longer directly connected to GPIOs but instead via an I2C GPIO expander. It could be that changes what is possible?

(UARTs are also handled differently if you have BT enabled ISTR, as the hardware UART in the BCM SoC is used for Bluetooth, so if you want BT you have to use a software UART for a separate UART connection? Though ISTR that you can disable BT to re-access a hardware UART, which has advantages with stable baud rates when overclocking?)
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by itsmedoofer » Thu Mar 16, 2017 9:40 am
Hi,

noggin wrote:The Pi 3 B doesn't do the 10 flash thing either does it?


My Pi3 flashes at me when it's safe to power off, with my Zero W the green LED just goes out, I have assumed this is the signal that it's done it's business....

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by DougieLawson » Thu Mar 16, 2017 9:56 am
The PiZ PiZC and PiZW only have one LED so it's different to all others. On my PiZ and PiZ with camera I've added a line in /boot/config.txt
Code: Select all
dtparam=act_led_activelow=on
to change the mode of the LED. I don't know if that's supported on the PiZW.

Have a read of /boot/overlays/README for docs for that dt parameter.
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by NickT » Thu Mar 16, 2017 11:16 am
DougieLawson wrote:The PiZ PiZC and PiZW only have one LED so it's different to all others. .

My PiZero (not wireless model) does flash its single LED on power down. That's why I was perplexed and slightly miffed that the ZeroW doesn't flash. It's always reassuring to get an ACK for a command and the ZeroW doesn't seem to do that like its non wireless predessor.
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by gregeric » Thu Mar 16, 2017 11:17 am
That dtparam solely affects how the linux kernel handles the LED re active lo or hi. It doesn't invert the VPU's notion of the LED's wiring: the power-down flashes are the same on the Zero irrespective of that setting.

I've no idea if the W's lack of the power-down flash sequence is by design, or unintended omission. Maybe it's due to the fact that the Zero has a phantom pwr_led at GPIO35, whereas the W does not.
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by solar3000 » Thu Mar 16, 2017 1:37 pm
Mine just powers off. LED off.
The other thing you could watch for is the USB device. It should go off too, except in the A series where the USB just stays on.
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by davidcoton » Thu Mar 16, 2017 1:44 pm
solar3000 wrote:The other thing you could watch for is the USB device. It should go off too, except in the A series where the USB just stays on.

Except, also, the Zeros, and the A models, and I think some of the early B models, if not all of them.
The USB turning off only works on models with a USB hub that includes power control -- B+(?), 2B and 3B do.
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by Slow Dog » Thu Mar 16, 2017 7:21 pm
Hmm. My Pi Zero W flashes it's LED as it's starting up, then the LED turns off. There's no indication that it's on at all. Nor any that it's turned off again.
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by rpdom » Thu Mar 16, 2017 7:27 pm
There have been some issues with the firmware not driving the Zero W's LED correctly. The initial release didn't show activity on the LED. The later release did, but doen't show the ten flashes at power down.

It will be fixed. I don't know if the fixed version has been released yet.
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by fruitoftheloom » Thu Mar 16, 2017 10:25 pm
rpdom wrote:There have been some issues with the firmware not driving the Zero W's LED correctly. The initial release didn't show activity on the LED. The later release did, but doen't show the ten flashes at power down.

It will be fixed. I don't know if the fixed version has been released yet.


There has been a few Raspbian Jessie updates in the last few days. :D
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by Slow Dog » Fri Mar 17, 2017 12:06 am
rpdom wrote:It will be fixed. I don't know if the fixed version has been released yet.


I've updated, and the LED now shows when the Pi's on and off, so that's a great improvement.
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by energyi » Tue Mar 21, 2017 12:47 am
In one of the many announcement articles on the release of the Rpi0 W I thought I saw something that said it had a new pad for on/off that the non-W didn't have. But I can't find that article anymore. Is there a new feature/pad on the W? And if so, how do you use it? Thanks in advance for any discussion.

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by mahjongg » Tue Mar 21, 2017 1:01 am
Simply wait long enough after powering down before pulling the plug, half a minute or so should be safe.
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by NickT » Thu Mar 23, 2017 9:11 am
I was rather hoping for an authoritative reply to this question from a Foundation member . When a question asking why the LED didn't light at all for the Zero W was asked, the reply in the manner of 'just wait a bit, we'll fix it soon' arrived fairly quickly.

I'm now left wondering whether the absence of flashes is a design feature, or is considered to be a bug and will be rectified at some time in the future.
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