How to organize a texture atlas for Sprite-Kit

Okay, I've been going on this for hours and I'm really confused. My code for the Background class is below:

class Background : SKNode {

    required init(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }

    override init() {
        super.init()
        buildBackground()
    }


    func buildBackground() {
        var sprite : SKSpriteNode = SKSpriteNode(imageNamed: "background_full")

        sprite.anchorPoint = CGPointZero
        self.addChild(sprite)
    }

}

      

        
        
        
      

    

I also have the following atlas files pointing to png files inside them

background@2x~iphone.atlas --> background.png, background-567h.png, background-667h.png
background@3x~iphone.atlas --> background.png
background~ipad.atlas --> background.png
background@2x~ipad.atlas --> background.png

      

        
        
        
      

    

I am getting unpredictable, irrational random results where images may not have been found for iPhone 4s in iOS 7, but works great for iOS 8 (however uses an image designed for iPhone 5). And the iPhone 5 will use the texture for the iPad @ 1x, etc.

I originally followed the solution for this post , but I just don't understand what went wrong.

Note: @ 3x is giving me an error, but I understand why the file is too big to be included in the atlas and I plan to split the background after I get the basics to work with. So you can ignore @ 3x as I didn't include it in my project, I just thought I was giving you the full picture.

EDIT - NOTE. I am testing iOS 7.03, 7.1 and 8.0

I have reduced my research to

background.atlas --> background.png (iPad 2)
background@2x.atlas --> background.png (iPhone 4s)

      

        
        
        
      

    

iPad 2 shows correct results, but its texture is used for iPhone 4s.

If I have a setup like this:

background@2x~iphone.atlas --> background.png (iPhone 4s)
background~ipad.atlas --> background.png (iPad 2)

      

        
        
        
      

    

iPhone 4s shows correct results but its texture is used for iPad 2 and for both devices I get an error in iOS 8.0 showing the app path on Simulator devices saying "SKTexture could not load image resource" ... / background @ 2x ~ iphone.atlasc / background @ 2x ~ iphone.1.png "'

For the two above, it seems that the texture in the atlas that comes first is the default

If I have a setup like this:

background.atlas --> background~ipad.png (iPad 2)
background@2x.atlas --> background@2x~iphone.png (iPhone 4s)

      

        
        
        
      

    

then everything works except iOS 7.03 where I get the error: "SKTexture could not load the image resource" background.png "and that it does not have a long path like in the previous example

Other editing

The last bullet point at the bottom of this page shows me that if I collect all my PNG files from all devices into one atlas, SpriteKit will split across the appropriate devices, so the correct textures will be loaded into memory. But then I would have to distinguish between all iPhone models (in particular the iphone 5 and 6, which are announced at @ 2x). Can I say that the corresponding PNG files for the device will be downloaded if I put them all together?

If not, I decided to split the PNGs into my own device atlas and write some code that distinguishes and loads the correct atlas.