Well,

Seems still to be lots of things to try before I jump out of the window ;-)

It's lunch time now and still a few hours to go before I get back home to try/check everything you suggest.

One thing is sure, I took a great care on the display's pins locations and this should not be wrong (the complete wiring is simple and I used colored wires to make it even more clear to check). Nevertheless, according to Charles's experience, I'll check this over again.

Meantime, about the DEFINEs, where can I see what is "behind" this or that particular command? The PBP book (chap. 4.16) doesn't tell much about this.

NB: I live on the groundfloor...