HD44780 LCD on Maple board

I'm running Espruino on the original LeafLab's Maple rev.5 board, and can control all the pins, with the help of attached pins-mapping table between STM32 GPIO pins, "official" Espruino board rev. 1.3, and Maple rev.5 board.
Now I'd like to connect the HD44780 LCD to my Maple board. According to the http://www.espruino.com/HD44780 and my table, the LCD should be connected to D0 (RS), D1 (EN) and D15-D18 (D4-D7 data lines), with the code modified as:

var lcd = require("HD44780").connect(D0,D1,D15,D16,D17,D18);
lcd.print("Hello World!");

However, nothing is displayed, and the Web IDE just spits out:

echo(0);
=undefined

What might be a problem? Any advise is very much appreciated. Many thanks in advance.

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