Raspberry Pi 3系のトラブルであるある第一位の電源トラブル、低電圧警報に関する情報のまとめ

Raspberry Pi用電源セット(5V 3.0A)－Pi3フル負荷検証済 ASIN: B01N8ZIJL8 　USBの電源ケーブルは 20AWGの太い電線で電圧降下が少ない物を使用しています。 　ちなみに電源ケーブルの直径は実測で 3mmです。 　高周波の音は感じませんでした。

Raspberry Pi用電源セット(5V 5.0A 4USBポート)－Pi3x2台フル負荷検証済 (Double Cable、White) ASIN: B073B2HNRG ケーブル 2本

Raspberry Pi用電源セット(5V 5.0A 4USBポート)－Pi3x2台フル負荷検証済 (Single Cable、Black) ASIN: B073B286NV ケーブル 1本

【国内正規代理店版】Raspberry Pi 3 Model B+ Base Kit V1 (本体/5V3A電源/ヒートシンク)【RS】 ASIN: B07F1NLW9C 初回購入にオススメの Pi3B+本体と 3A電源のセット

Raspberry Pi 3系でトラブル無用で安定して使える電源を購入、3.0A、Physical Computing Lab製

Solution:
We can restrict the log level of the kernel by adjusting the loglevel as a boot parameter. This can be done by modifying the /boot/cmdline.txt file.
sudo nano /boot/cmdline.txt
and at the end set loglevel=1 , so the messages will disappear.

GPIO 135 is the PWR_LOW_N line, so
git clone https://github.com/6by9/rpi3-gpiovirtbuf.git
cd rpi3-gpiovirtbuf
make
./rpi3-gpiovirtbuf g 135

Wed Mar 07, 2018 10:40 am
There is now under-voltage logging in the latest rpi-update:
https://github.com/raspberrypi/linux/pull/2397

[  530.474085] Under-voltage detected! (0x00050005)
[  534.634106] Voltage normalised (0x00000000)
file = open("/sys/devices/platform/soc/soc:firmware/get_throttled")

What:		/sys/devices/platform/soc/soc:firmware/get_throttled
Description:	This file returns the firmware get_throttled value which is
		divided into 2 parts:
		- lower 16-bits are the live value
		- upper 16-bits are the history or sticky value

		Bits:
		0: under-voltage
		1: arm frequency capped
		2: currently throttled
		16: under-voltage has occurred
		17: arm frequency capped has occurred
		18: throttling has occurred

		This file can be polled for changes.

What:		/sys/devices/platform/soc/soc:firmware/get_throttled_mask
Description:	This file does two things:
		1. Describes which bits should denote a change when polling
		2. The upper part is used when clearing the sticky bits

		Default value is 1 << 16.

What:		/sys/devices/platform/soc/soc:firmware/get_throttled_poll_ms
Description:	Specifies the get_throttled polling interval in milliseconds
		(default 2000ms). The kernel polls this value to detect
		under-voltage and to support polling the get_throttled file for
		changes. Setting this to zero disables polling.

+	if (new_uv != old_uv) {
+		if (new_uv & UNDERVOLTAGE_STICKY_BIT)
+			pr_crit("Under-voltage detected!\n");
+		else
+			pr_info("Voltage normalised\n");
+	}

Even if I ask to clear the sticky bit, it is stuck for ~5 seconds:

$ while true; do vcgencmd get_throttled 1; sleep 1; done
throttled=0x40000
throttled=0x40000
throttled=0x40000
<brief overload>
throttled=0x50005
throttled=0x50005
throttled=0x50005
throttled=0x50000
throttled=0x40000
throttled=0x40000
throttled=0x40000
throttled=0x40000
^C

$ vcgencmd get_throttled
throttled=0x0

$ vcgencmd get_throttled
throttled=0x50005
Okay, the bits in this number represent:
Code: Select all

0: under-voltage
1: arm frequency capped
2: currently throttled
16: under-voltage has occurred
17: arm frequency capped has occurred
18: throttling has occurred

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