USB Receipt Printer Sniffer

marceloduarteuy · Joined: 30 Jan 2015 Posts: 2

USB Receipt Printer Sniffer
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I need to sniff communication between a USB receipt printer and the POS Terminal in order to be able to get all printed data information.
I cannot install anything on POS Terminal, so I need to trap all the information when it is coming to the Printer.

This must be transparent for the POS Terminal.

I would like to interconnect a FTDI VDIP2 Vinculum VNC1L device in the middle of the Printer <--> POS Terminal, to monitor and extract to the UART interface this device has, all printed data and because of that VDIP2 Vinculum VNC1L firmware required to be developed.

It is important to remark, I need to receive on the monitor only Printer data, filtering out all USB protocol communication related data.

(FTDI VDIP2 Vinculum VNC1L http://www.digchip.com/datasheets/photos/1948/VDIP2.jpg)

Another solutions proposals are welcome also.

Please send job proposal by private message.
Thanks

Marcelo

temtronic · Posted: Fri Jan 30, 2015 8:18 am

hmm... I started something like that couple years ago..I was using a PIC18F46K22 as the 'brains.

Simply put..

PC --> VDIP port1 --> PIC uart1--->PIC uart2 -->VDIP2 port2 --> USB PTR
|
---> TTL<>USB module ( sniffed data)

to 'sniff', just send a copy of all data from PIC uart1 to a 3rd serial port.
I was using one of those $2 TTL<>USB modules.

Sorry, don't have any code as it was a 'proof of concept' for a client.

HINT; You NEED ISR driven buffers ! That code snippet is on the forum !!

Jay

marceloduarteuy · Joined: 30 Jan 2015 Posts: 2

Thank you temtronic for your advice !

BTY.. Do you know somebody who want to develop this as freelance ?

temtronic · Posted: Fri Jan 30, 2015 9:59 am

If this is a 'one -off' device, cheaper to just buy one of the units commercially available.
It'd be cheaper than having one made. While the parts are inexpensive( +-$100) there's a couple days of coding to cut,testing,etc. so maybe $1000 in 'R&D'.

Jay

Ttelmah · Joined: 11 Mar 2010 Posts: 19537

There is a lot of work to this. The device would either have to sniff the USB bus as a non USB device (looking at the raw data - the PIC hardware couldn't do this), or would have to work as Temtronic illustrates passing the specific target data 'forwards', which means a USB host would have to be implemented as well (Temtronic was using two Vinculum devices so could do this).
A _lot_ of work.

Do a search on the Beagle USB12. This is a complete off the shelf unit to do this, and would cost a lot less than trying to develop this, unless you need a lot of units.

esiwind · Joined: 23 Nov 2015 Posts: 1

asmboy · Joined: 20 Nov 2007 Posts: 2128 Location: albany ny

The snooper MR. T suggests will get you well down the road you think you want to be on.. BTW don't forget to snatch data in BOTH directions ;-))

B U T.....

Then there is the not so small matter of interpreting the data you collect.

if you are really lucky, it will be some form of VCOM or vcom-like actual transmission structure.

if you are S.O.L. it will be binary or worse -,
potentially single-key encrypted.

what is the make and model of the terminal in question?