NRC received events ( NRF.on('NFCrx') )

I'm using Puck.js (Espruino v2.01) and I want to be able to manipulate variables based on data that is written to the NFC tag using NFCrx.
If I use the 'NFCon' event, and console log based on that, everything works when I scan NFC:

>NRF.on('NFCon', () => { console.log("test"); });
=undefined
test
test
test

But when I use the NFCrx event instead, after NFCStart of course, the event callback is not called (almost as if the event is not registered):

>NRF.nfcStart();
=new Uint8Array([95, 193, 71, 81, 42, 138, 1, 165, 4, 3]).buffer
>NRF.on('NFCrx', (rx) => { console.log(rx); });
=undefined
>NRF.on('NFCrx', (rx) => { NRF.nfcSend("test"); });
=undefined
>NRF.on('NFCrx', (rx) => { console.log("test"); });
=undefined

What am I missing?
Thanks in advance

That's odd - I guess you could try using nfcStop first just in case NFC was already set up?

Personally I haven't used it but this module does:

• http://www.espruino.com/NFCTag
  
• http://www.espruino.com/modules/NFCTag.js
  
  

Do you could use that as a reference?

Hi Gordon - Only just got around to looking at this one again - it seems to be working now (for whatever reason...)

I have a much better understanding of how this all works too - I'm working on a way today read the data transmitted via NFC and action upon it based on whether it matches an expected format.
I've got reading and writing working fine - but I'm tripping over the format of the data that's actually being sent. I'll spill my thoughts here, in case anyone else stumbles across this.
When a 'write' command is sent to the chip, (if it complies to NTAG213/215/216) it'll be formatted like so:
[[command code] [address of data to be changed] [data] [crc]]
Pretty basic so far. But the NFC writer app that I'm using to test actually writes some prefix and suffix data, which makes it hard to find the data that I have specified to be written, as it is surrounded by metadata. Here is an example of a write sent to the chip (actually ends up being 4 write commands):

new Uint8Array([162, 4, 3, 10, 209, 1]).buffer
new Uint8Array([162, 5, 6, 84, 2, 101]).buffer
new Uint8Array([162, 6, 110, 112, 111, 111]).buffer // <-- my data, following the 110, in ASCII
new Uint8Array([162, 7, 254, 0, 0, 48]).buffer

So the question I'm looking into is, what is the prefix/suffix data? And even if I wish to ignore this, there is no callback function on the tag to detect that it has finished being written to, so it's hard to locate my data afterwards - or even know when afterwards is.
I'll keep the thread posted, for archive sake!

Hi @Gordon
I've figured out what the data in the arrays are.

new Uint8Array([162, 4, 3, 10, 209, 1]).buffer
162: NFC command for "write"
4: Index for where to put data within tag array
3: Type length
10: Record length
209: NDEF record header
1: Type Name Field

new Uint8Array([162, 5, 6, 84, 2, 101]).buffer   
6: Payload Length
84: Well known record
2: Well known record type (in this case - the encoding for this text (UTF))
101: e 

new Uint8Array([162, 6, 110, 112, 111, 111]).buffer
110: n - ("en" is locale)
112: p
111: o
111: o

new Uint8Array([162, 7, 254, 0, 0, 48]).buffer 
254: Marks the end of the payload

Further information on this can be found here.
I am now able to send custom commands/string through NFC to Puck.js.

That's great! If you get a moment it'd be really good if you could post up some example code for how to handle this on both sides :)