Turning backlight on/off via GPIO

[dbrgn]

Be careful: Current should not be drawn from GPIO! Probably needs separate circuit.

[stripwax]

easily done by using GPIO to switch between gnd/5v line using a transistor and some resistors. Is RPLCD still in active development?

[dbrgn]

easily done by using GPIO to switch between gnd/5v line using a transistor and some resistors

Yep, but needs additional hardware. If we do this, we'd need to properly document it.

Is RPLCD still in active development?

Right now not very active, but I do intend to fix all bugs that may occur :) Also I want to add I2C support soon, if I find the time to do so.

[thijstriemstra]

does someone have details or a fritzing sketch on how this would be done?

[stripwax]

If your LCD backlight can be driven by 3.3v then you can do it directly I. E connect the back light gpio pin to the back light LCD pin. If not, use a transistor to switch the 5v supply to the LCD back light pin.

⁣​

On 20 Oct 2016, 22:04, at 22:04, Thijs Triemstra notifications@github.com wrote:

does someone have details or a fritzing sketch on how this would be
done?

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[dbrgn]

If your LCD backlight can be driven by 3.3v then you can do it directly I. E connect the back light gpio pin to the back light LCD pin. If not, use a transistor to switch the 5v supply to the LCD back light pin.

That's what I meant with "we need to properly document it". Not all LCD modules work the same. People need to read datasheets, so they don't fry their boards by simply following instructions :)

Maybe we could add a separate file called wiring.md that includes Fritzing sketches for the most common combinations, with clear instructions to read the datasheet before just trying out something.

[dbrgn]

I wonder if we should really have official support for this. It requires additional circuits and is mostly a documentation problem. Especially now that we have I2C support (#34). An I2C port expander board is really cheap (can be found for <1$) and makes handling of backlight control as well as wiring much simpler - 4 wires is all that you need. There are even a lot of LCDs with those "backpack boards" already soldered on.

I'll close this for now, feel free to comment if you disagree.