PCD8544 - attempts to fix module running into strange js behavior

It's because the Uint8Array is a 'view' of the original array rather than a new array. You're trying to make it go past the end of the existing array, so if you set bytes in it they're ignored.

I guess the best you could do is:

var last=new Uint8Array(84+2);
last.set(new Uint8Array(this.buffer,i*84,84+2));
last[84]=this.buffer[0];
last[85]=this.buffer[1];
spi.send(last, ce); 

Or, you could set CE manually, which is probably better (in fact you may not even have to bother):

ce.reset();
spi.send(new Uint8Array(this.buffer,i*84,84+2)); 
spi.send(new Uint8Array(this.buffer,0,2)); 
ce.set();

Looks like this isn't 100% JS compliant though - in proper JS there seems to be a difference between:

new Uint8Array(uint8Array,i*84,84+2) // silently ignores first and second arguments, returns a *copy* of uint8Array
new Uint8Array(uint8Array.buffer,i*84,84+2) // does what Espruino does - creates a view

I guess I should probably change the drivers over and then tweak Espruino's implementation - I prefer my version though ;)

By the way, on my LCD it works great without the extra 2 bytes, so I wonder whether it's just some driver chips that have the issue - or maybe it's something to do with initialisation.