Recommended Assembly 499 and 292

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chrisfromiowa
 
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Recommended Assembly 499 and 292

Post by chrisfromiowa »

I have the 20x4 Character LCD item #499 with the RGB background. I also have the i2c/SPI character LCD backpack item #292. As the tutorials have already pointed out the backpack can't control the RGB backlight for pins 15-18.

I'll be using this with the Arduino Uno. I was wondering how to solder the backpack to the LCD. If I solder all 16 pins will the backpack work as if the LCD were a single LED backlight display?

If not, I guess the answer is I must only solder pins 1-14.

If it does work with all 16 pins connected, would I still be able to connect pins 17 and 18 directly to the Arduino to 'turn on' the Red and Blue LEDs (with some additional code anyway)?

Thanks

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adafruit_support_mike
 
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Re: Recommended Assembly 499 and 292

Post by adafruit_support_mike »

ChrisfromIowa wrote:If I solder all 16 pins will the backpack work as if the LCD were a single LED backlight display?
Yep.. a red one.
ChrisfromIowa wrote:If not, I guess the answer is I must only solder pins 1-14.
Actually, you want to connect pins 1-15. RGB LCD pin 16 controls the red backlight LED, pin 17 controls the green one, and pin 18 controls the blue one.
ChrisfromIowa wrote:If it does work with all 16 pins connected, would I still be able to connect pins 17 and 18 directly to the Arduino to 'turn on' the Red and Blue LEDs (with some additional code anyway)?
Green and blue, but yeah, you can do it that way.

As a matter of personal taste, I wouldn't. It would make controlling the backlight color kind of funky.. send the R value through the I2C channel, set the G and B values on pins X and Y. It would also impose a lot of data traffic if you wanted to use PWM to control the backlight color/brightness.

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chrisfromiowa
 
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Re: Recommended Assembly 499 and 292

Post by chrisfromiowa »

Mike, thanks for the advice. One clarification though.
Actually, you want to connect pins 1-15. RGB LCD pin 16 controls the red backlight LED, pin 17 controls the green one, and pin 18 controls the blue one.
But from this page:
http://www.adafruit.com/products/292
You can try to connect our RGB 16x2 or 20x4 LCDs up but this backpack will not control the RGB backlight so you'll have to use the backpack only for the 14 digital IO pins (pins #1-14) and connect the backlight pins (#15-#18) directly to your microcontroller with 4 extra wires for color/PWM control as if they were just an RGB LED.
So now I'm a little confused about pin 15. To solder, or not to solder. That is the question.

Thanks

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adafruit_support_bill
 
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Re: Recommended Assembly 499 and 292

Post by adafruit_support_bill »

Pin 15 is the "common anode" - that is the common positive connection for the R, G & B leds. You can solder it on the backpack. It gets connected to 5v one way or the other.

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chrisfromiowa
 
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Re: Recommended Assembly 499 and 292

Post by chrisfromiowa »

Okay, I've soldered it together. Thought I'd post a pic with an additional thought for posterity.
AssemblyPhoto1.jpg
AssemblyPhoto1.jpg (33.52 KiB) Viewed 1303 times
Pins 16,17,18 soldered on the other side before connecting the backpack (or it would have been impossible to get the iron on the leads)



Here's a pic of the final assembly, complete with color-coded leads for the backlight (didn't double check order though).
AssemblyPhoto2.jpg
AssemblyPhoto2.jpg (47.44 KiB) Viewed 1303 times
Thanks for all the help!

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