Additional device for Espruino to support 8 pins in parallel (for discussion)

Great! So you're not really using the direct_io branch now, but just standard Espruino? It's a shame - can you see the pins changing state?

The brightness is probably because those rows are left on for slightly longer... I guess en controls if the row is actually lit? If so, just adding arr.push({callback:en.set.bind(en)}); should fix it?

I guess the lack of brightness is because now we're actually able to push the data out quickly - flickering might be because something is stopping scan from getting called when it should be.

My next step will be to create a graphics driver, using Graphics.createCallback to get rid of prep step.

I'd have thought that might be quite slow... On Pixl.js/etc we just have g.flip() that you call when you want to display what you rendered (which is basically what prep() is doing) - or even if you want to avoid that you could check g.getModified() to see if anything has changed?