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Based on this, read in the reference:

If sck,miso and mosi are left out, they will automatically be chosen. However if
one or more is specified then the unspecified pins will not be set up.

I thought that I can connect the unused MISO line of an SPI to the CS of an LCD screen but it does not work.

  SPI2.setup({ sck:B13, mosi:B15});
  // Initialise the LCD
  // connect(/*=SPI*/_spi, /*=PIN*/_dc, /*=PIN*/_ce, /*=PIN*/_rst, callback)
  g = require("PCD8544").connect(SPI2,B10,B14,B1, function() {

to make my LCD work I had to change B14 to another pin.

As far as I understand the scanner has an RS232 interface.
Do you have any electrical level converter?
RS232 is +/-12V signal. Such a voltage can blow up Espruino and USB.