Proto-ScrewShield and 16x2 LCD shield

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jeffrey
 
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Proto-ScrewShield and 16x2 LCD shield

Post by jeffrey »

I am getting my posterior kicked. I have a Leonardo, a Proto-ScrewShield, and a LCD Shield stacked in that order. I can't get the LCD to work. It is getting power (I can see a light background when I crank up the contrast). The LCD shield works when connected directly to the Leonardo. The D13 LED on the Proto-ScrewShield flashes, so it is getting power (not that it should matter for the LCD). What am I missing?

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adafruit_support_bill
 
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Re: Proto-ScrewShield and 16x2 LCD shield

Post by adafruit_support_bill »

Hmmm. The stacking headers on the screw-shield should pass all the signals through directly. Do you have anything else connected to the screwshield? If you post some photos of your setup and the individual boards we can try to spot the problem.

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jeffrey
 
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Re: Proto-ScrewShield and 16x2 LCD shield

Post by jeffrey »

And the plot thickens. I tried my ScrewShield and LCD with an Uno and it works. So, there is some difference between the Leonardo and the Uno. I am not familiar enough with the two yet (just started messing with these things) to know what it is. I did notice that the Leonardo has two pins, SCL and SDA, next to the AREF pin. The Uno has them but they aren't marked. And I have noticed that some of the shields that I have (RS232 from CuteDigi, TransmogriShield from SparkFun, Arduino SensorShield from Keyes, Go Between Shield from Mayhew) don't have the SCL or SDA pins, so they don't get passed on. Only the LCD shield and the Ethernet Shield R3 have them.

What pins does your LCD shield use? I thought they used analog pins 4 and 5. I verified those pins are passed through the ScrewShield. I wrote some code to cycle digital pins 2-13 on/off every second and, using an LED/resistor, checked each digital pin while the ScrewShield was attached to the Leonardo. Each pin, when connected to a digital pin on the ScrewShield, blinked as expected. And so did the SCL and SDA pins, so it appears they are hardwired on the Leonardo to a couple of the digital pins. At this point, I will use the Uno for my project, but it makes me wonder what else is there on the Leonardo that'll bite me later.

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adafruit_support_bill
 
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Re: Proto-ScrewShield and 16x2 LCD shield

Post by adafruit_support_bill »

What pins does your LCD shield use?
The shield uses SDA and SCL. On the Uno and 'classic' Arduinos, these signals are on A4 and A5. On the Leonardo, they are on digital pins 2 and 3. On the Mega they are pins 20 and 21.

Needless to say, this caused a lot of incompatibility issues with shields. Starting with R3, Arduinos of all kinds have these signals replicated to two extra header pins next to the AREF pin. The RGB/LCD will work with either the 'classic' A4/A5 pins or the R3 dedicated pins. Unfortunately, the screw-shield is a pre-R3 design and does not pass-through the 2 extra pins.

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jeffrey
 
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Re: Proto-ScrewShield and 16x2 LCD shield

Post by jeffrey »

When I did my testing with an LED, I only flashed the digital pins. Yet, when I did that, the SCL and SDA pins also flashed. I wonder if they are connected on the Leonardo? And, if your LCD module uses the digital pins, I don't see why it refuses to work with the ScrewShield. Those pins are passed thru that shield. How does your LCD shield differentiate between an Arduino board's selection of pins for SCL and SDA?

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Re: Proto-ScrewShield and 16x2 LCD shield

Post by adafruit_support_bill »

And, if your LCD module uses the digital pins
As noted above "The RGB/LCD will work with either the 'classic' A4/A5 pins or the R3 dedicated pins." It does not support the pre-R3 Leonardo or Mega configurations.
How does your LCD shield differentiate between an Arduino board's selection of pins for SCL and SDA?
It doesn't. The R3 SDA/SCL pins are connected to A4/A5. You can't use both at the same time unless you cut the traces.

davidc1
 
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Re: Proto-ScrewShield and 16x2 LCD shield

Post by davidc1 »

Unfortunately, the screw-shield is a pre-R3 design and does not pass-through the 2 extra pins.
Does Adafruit have plans to produce a version of the shield that does pass these pins through?

David

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adafruit_support_bill
 
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Re: Proto-ScrewShield and 16x2 LCD shield

Post by adafruit_support_bill »

These boards are designed and produced by WingShield Industries. If they update to an R3 compatible pinout, we will likely carry them.

http://wingshieldindustries.com/products/screwshield/

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