Need help connecting Fingerprint Scanner - TTL (GT-511C3) over UART Serial Comms

Something like this should do the trick.

let GT511CXX = require('./gt511cxx.js'),
        fps = new GT511CXX(GT511CXX.Devices.GT511C3, Serial1);

fps.open().then(() => {
        fps.getTemplate(0).then(template => {
            console.log('template', template);
        }).catch(err => console.log(err));
}).catch(err => console.log(err));

This example should return you the template in the first slot (slot: 0).
It should return an error if there is no template in the given slot.