Pixl.js & MCP23017 connected using I2C

Hi,
I have connected a port expander MCP23017 to pixl.js using I2c (using D5 for scl : D5 and D4 for sda)
My target is to use MCP 23017 for reading or writing some signal.

There are instructions in https://www.espruino.com/MCP23xxx but it doesn't work for reading or writing:
It doesn't reports error messages, here is the code:

   var i2c = new I2C();
   i2c.setup({ scl : D5, sda: D4 });
   var address = 0x20; //this is the address, set by the address pins.
   // for MCP23017
   var port=require("MCP23017").connect(i2c,nul­l,address);
   port.B0.mode('output');
   port.B0.write(1);      //<--IT MUST CHANGE TO '1' BUT B0 CONTINUE AT '0' LEVEL 
  port.A0.mode('input_pullup');
 console.log(port.A0.read());    //<--ALWAYS READ '1'

I wrote a new code and now is working just for reading signals:

   var i2c = new I2C();
   i2c.setup({ scl : D5, sda: D4 });     
   i2c.writeTo(0x20, 0X12); 
   var x = i2c.readFrom(0x20, 1);  
   i2c.writeTo(0x20, 0X13); 
   var y = i2c.readFrom(0x20, 1);

But for writing , it doesn't work:

   var i2c = new I2C();
   i2c.setup({ scl : D5, sda: D4});
   i2c.writeTo(0x20, 0x00);
   i2c.writeTo(0x20, 0x12);      // program all Bank A to output
   i2c.writeTo(0x20, 0x00);
   i2c.writeTo(0x20, 0x00);
   i2c.writeTo(0x20, 0x12);      // Change all pins of Bank A to '1'
  i2c.writeTo(0x20, 0xFF);

i2c.writeTo(0x20, 0x13);      // program all Bank B to output     
i2c.writeTo(0x20, 0x00);
i2c.writeTo(0x20, 0x00);
i2c.writeTo(0x20, 0x13);      // Change all pins of Bank B to '1'
i2c.writeTo(0x20, 0xFF); 

Some help, please?
Thans in advance.

Paco