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I'm a newb with electronics and was wondering if there's an IC or PCB that could convert a parallel LCD connection to Serial so I can use 2 wires to communicate with the screen using an arduino and still have open pins on the arduino to use for something else. If this isn't the case, then do people usually have a dedicated microcontroller for the LCD screens or do they handle this a different way entirely?

EDIT: For example, this LCD screen requires approximately 11 pins which is a lot to use on an arduino.

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3 Answers 3

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Yes, there are a number of serial-to-LCD solutions for character LCDs. Adafruit sells one based on a Microchip I/O expander rather than a microcontroller to talk in two-wire I2C.

enter image description here

There are add-on boards using a processor, which can communicate in asynchronous serial at commonly used baud rates.

You can also purchase serial-input displays from, for example, Newhaven (available through distributors), which have additional features such as serially adjustable backlight brightness and display contrast.

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  • \$\begingroup\$ Seems easier to buy the right sort of screen, or a micro with more pins, than a separate converter. \$\endgroup\$
    – John U
    Commented Jan 20, 2014 at 11:34
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Well, here's the pin out: -

enter image description here

And, the pins that need control are DB0 to DB7, RS, R/W and E.

You can use a serial in parallel out shift register (such as 74xx595) - this means you load the data word (DB0-7) using one pin for data and another pin acting as a clock for the serial register.

The other three pins are probably best left as dedicated IO pins so, in total you can get away with 5. That's a lot better than 11.

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For example, this LCD screen requires approximately 11 pins which is a lot to use on an arduino.

Actually there are two modes you can use to drive an LCD,

the 8bit mode that uses 11 lines
enter image description here

and the 4bit mode that used 7 lines (or six if you use write only mode)
enter image description here

If seven lines is still too much then you can use just three pins with a serial shift register that receives the data serially and outputs them in the parallel outputs.
enter image description here

And if you want even lower then you can use just a single pin , but in this case the code will be more complicated due to the strict timing that has to be followed
enter image description here

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