Powering up the Kraken at the same time as the Pi

I’d read (somewhere) that you had to power up the Kraken before the Pi so the Pi would recognize the Kraken. After doing that and then getting tired of the 2-step process, I thought about slowing the Pi’s boot process in software.

So, using raspi-config, I set the boot order on the Pi to look for a [nonexistent] network boot node before booting from the SD card. That slows it down about 5 seconds. There’s also a boot_delay setting in /boot/config.txt that can slow things down.

I haven’t completely verified this yet, but after making these changes, I can power both devices at the same time and the Kraken is there when the Pi goes looking for it.

I’ll keep poking around on this to confirm or correct this info. But, a software delay is a much cheaper, simpler, and more elegant solution compared to some of the other ideas I had for how to power it on/off remotely.

After taking a bit more methodical approach to this, I found:

  • Changing the boot order in raspi-config didn’t change the boot time noticably
  • Changing the value of boot_delay in /boot/config.txt works as advertised: With a value of 5, it takes 5 seconds longer to boot. A value of 10, 10 seconds longer.

The interesting thing was that even with a delay of 0, all of the Kraken devices appeared to be registered. So, I’m not sure what to make of the “start the pi after the Kraken” advice. But, since it’s an easy change and an imperceptible inconvenience, I think I’ll delay the boot 5 seconds just in case. At least until there’s some additional evidence that it’s unnecessary.

The “start the pi after the kraken” advice is simply to ensure that people using two separate power supplies have the Kraken connected first. If someone starts the Pi, then takes a while fiddling with the Kraken power supply, or decides to plug in the Kraken later, it will cause a connection issue.

But if you have a master power switch that can ensure that you power both on at the same time it will be no problem.

You actually have a window of a few seconds while the Pi boots to plug in the Kraken.

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Thanks for the note. That’s good info to help configuring the Kraken as part of a system.

Because there are no user-accessible controls on the Kraken or the Pi, I wanted to be able to tuck the two devices out of sight and power them up/down remotely. Knowing this, now I just need a switch. Misunderstanding the initial advice, I was thinking that I’d need some sort of time-delay relay to turn things on in sequence.

Thanks for clarifying (and simplifying) things.