Need 16 GPIOs Next to each other on P8

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1

Hi,

I would like to configure BBB P8 with 16 (2 rows of 8) GPIO pins next to each other. They just need to be able to be set to high or low. I see P7 through P18 but I need 4 more. I am not using any LCD screen. Is it possible to reconfigure the pins? I am a BBB newbie and would appreciate any help so I don’t mess anything up.

Thanks

2

As is indicated in the System Reference Manual, you can use the LCD pins as GPIO pins. Provided, you don’t interfere with their settings during power up as they are also the boot pins.

Gerald

3

When reconfigured, would the LCD pins change states during boot up? For example, if I had relays attached, would the pins open and close the relays during boot?

Thanks

4

When reconfigured, would the LCD pins change states during boot up? For example, if I had relays attached, would the pins open and close the relays during boot?

Don’t load the HDMI device tree overlay and then all GPIO remain in their reset state which means all GPIO are defined as an input.

Regards,
John

5

Provided, you don’t interfere with their settings during power up as they are also the boot pins.

He’s saying you shouldn’t interfere with their state at boot. No driving, pullup, or pull down on any of these pins (besides the those that configure the sysboot setting on the board).

Relays wont flip, but there are 100k pullups on some of the pins, so they could be in a state you don’t want.

You could isolate these pins with something like a bilateral switch (or a Va = Vb type unidirectional level shifter) during boot. Attach the enable to 3v3_exp, and make sure whatever is on the world side of the isolator is in a known state when the pins are at high impedance (using pull ups or down).

For any pins that you want to switch simultaneously (which requires memory writes), make sure they’re in the same gpio bank.

-Brandon