Using external pull down resistor board?

[Schorschi]

Not being one that loves soldering, I found this small external pull down resistor board.
http://microcontrollershop.com/product_ ... fgodD3MFSQ

I was wondering if this could be used to protect against floating state of GPIO pins on Raspberry Pi boot? I have a few projects that need GPIO pins to always be in a known state on boot, and this seems like one solution, versus creating something from scratch?

For the above question, I guess the 10K version of the board, would seem appropriate, no?

[pcmanbob]

Hi.

while this board may well do what you want I very much doubt this will just plug on to the pi's GPIO header and be pin compatible,
it looks to have been designed to work with their micro controller so the pin lay out will be different.

[gregeric]

Also, only GPIOs 28,29 44 & 45 float. 0-8 have default internal 50k pulls high, the rest default pull low. Additionally, there are strong pulls up for whichever I2C peripheral appears at pins 3 & 5 on the GPIO header (GPIOs 2&3 on the majority of Pi models).

The pulls on 28, 29, 44 & 45 are already taken care of on consumer Pi models - you only need take care of that yourself if designing a carrier board for the Compute Modules.

[Schorschi]

Mapping the board to GPIO pins was expected to be needed, I did not expect to just drop it in, like say a Pi face board or such. And the board apparently is no long available as well, which makes that potential option a dead end.

I was looking for a very simple way to make sure any GPIO pin is pulled down or up by default, regardless of default configuration during Pi reboot. I have seen a lot of discussion on this topic. But I don't want to have to solder anything, or start from scratch creating my own PCB.

I have a number of projects where a generic board like this would be easy to use. For example...

- Connecting a 8-way relay board, to a Pi, I figure I can selectively pick pins that have a known boot state. But with external resistor board, don't have to worry about explicit selection or assignment.

- There seems to be a way to map pins default state very low in the boot process? https://www.raspberrypi.org/documentati ... ce-tree.md

- I can just cheat and cross connect 10K resisters inline between GPIO pin, GND or VCC depending on the application or need

I want to avoid using the I2C pins, since I have plans for the I2C bus as well. I am using a Pi Zero, but I have not found a specific pin state reference for Pi Zero? Is it different or same as other Pi models? Same right?

[gregeric]

Yes, the Zero is the same as others: 0-8 pulled high, 9-27 pulled low.

If possible, choose your GPIOs so that your desired initial pull is the default one - the device tree stuff may take a second or so to become active. Failing that, install your stronger pull resistor either directly on the Pi or on whatever active board you're connecting - no need for that passive "Pull-Up/Pull-Down Resistors Board".