Contrast support via PWM

[dbrgn]

Needs separate circuit.

[dbrgn]

Is this GPIO specific, or would it work via common I²C port expanders too?

[ageir]

This will work with expanders like mcp2308, but the PWM signal has to go via an external RPi GPIO directly to the LCD. Expander GPIOs doesn't support PWM. Will not work for backpacks, since they have trimpots onboard connected directly to the display.

[dbrgn]

Hm, I'm not really sure whether this feature is worth developing. What would be compelling use cases? Temperature compensated contrast?

[ageir]

It's not a very straightforward solution because people have different setups, backpacks, gpio, etc.
But it would be nice to have contrast and backlight support in one package, RPLCD.

[a-sp]

This enhancement request is quite old, and I see the RPLCD now supports PWM using pigpio library... Now my question is: would it be possible to support PWM also using GPIO without any additional library?

See here for an example on how to use PWM via GPIO.