LCD and OLED displays shut down Pi

#1

When connecting RGB LCD or OLED display to any I2C connector, board shuts down. GrovePi+ and RaspberryPi 2B. Latest GrovePi firmware and Raspian for Robots image.

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#2

Hi @cnc,

What do you mean it shuts down? Does it crash or is the shutdown procedure triggered? And are you referring to the Raspberry Pi that it shuts down? You need to give us more details.

Also, have you tried connecting different devices to that port and see if it works? Other devices than those 2?

Thank you!

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#3

As soon as I insert the connector, the Pi turns completely off, as if a short of the Vcc. Removing the connector, it reboots. I’ve tried other non I2C components and nothing happens. I have plugged these two displays into a BBG I2C port without this happening. Checking the pins of the displays with a multimeter doesn’t show a short.

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#4

I did some further testing, loaded new sd card and did a new setup. The same thing happened but I left the display connected and the Pi rebooted and I was able to run the OLED hello world program. Samething with the RGB LCD. Apparently the I2C ports don’t like to be hot plugged.

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#5

Hi @cnc,

That to me looks like a power supply issue. Long story short: I think the Pi + GrovePi aren’t getting enough current from the power supply.

With what are you powering it up?

Thank you!

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#6

Pardon me for chiming in on this, but - depending on the Pi version you have, power supply issues are not uncommon.

Particularly with the Pi-3 3-B, “+” versions, etc. - this is particularly true.

Beginning with the Pi-2 versions and onward, power supply requirements have increased dramatically - even without a Grove or GoPiGo board attached. For example, the Pi-3 family of boards require a 5v supply rated to at least 2 amps.

To make things even MORE interesting, not all 2 amp supplies are created equal. Though I haven’t been able to stick an ammeter in the supply leg, I strongly suspect that some supposedly “2 amp” supplies have their spec rounded up to 2 amps. (i.e. 1.76 amps rounded up to 2.)

A further example is in order:
When I bought my first Pi-3, they were originally spec’d at slightly less than 2 amps - something like 1.75 if I remember rightly. (Of course, my memory has been going down the tubes :scream: :smirk: so take this with a grain of salt!)

Wanting to be generous, I plugged in a supply marked at 2 amps and watched it burp, struggle, and fail to boot with some off-brand SD cards. Of course, I got right on the Pi fora and asked about it.

The replies fell into two broad categories:

  1. Some SD cards are wonky and won’t boot.
    That was puzzling because they were booting in every other Pi I owned.
  2. By far the largest number of answers was “under-powered” (i.e. Power supply doesn’t have the testicular fortitude to supply the required current.)
    That also puzzled me because I tried several  supplies that were (allegedly) rated at 2 amps.

Finally, I had an opportunity to pick up an “Official” Pi-rated 2 amp supply and - wonder of wonders! - things were peachy-keen and my Pi boards worked like a champ!

I had similar issues with the GoPiGo when I first assembled it. It would behave in unpredictable ways that were ultimately traced to batteries that didn’t have the cojones to power the entire device when running. (i.e. Alkaline batteries, even the “Super Duper” kind, can’t handle the current draw. Use NiMH batteries instead.)

Hope this helps the next person with this problem.

Jim “JR”

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