In hope this is appropriate
I have a Bosch Tassimo TAS2002EE coffee maker that uses T-Disks. Those contain coffee/milk/something else, and a barcode that is supposed to tell the machine how to deal with the disk.
What I want to do is understand the barcode and come up with some different barcodes that would be accepted as valid and let me adjust e.g. drink volume.
At first I wasn't able to find any decent information about these barcodes, among the top Google hits were things like this rather useless rant. Surprisingly, when searching for pictures of T-Disks (in order to study more barcodes), I stumbled upon this useful post: Hacking the Tassimo - Part 2: Breaking the Code (archive), which also links to this T-Disk-related patent, in which there is a table explaining the controlling bits. While this was quite promising, it resulted in nothing, as the blog author found out himself, too. (Part 3 archive)
On top of the information from the links above, here's what I found out myself.
╔═════════╦══════════════════════════════════╦════════════╦═══════════════════╗ ║ Barcode ║ Product ║ Output, ml ║ Barcode binary ║ ╠═════════╬══════════════════════════════════╬════════════╬═══════════════════╣ ║ 06409 ║ coffe créma ║ 150 ║ 00011001 00001001 ║ ║ 06178 ║ espresso ║ 80 ║ 00011000 00100010 ║ ║ 63735 ║ milk for latte (big disk) ║ ? ║ 11111000 11110111 ║ ║ 06182 ║ milk for cappuccino (small disk) ║ ? ║ 00011000 00100110 ║ ║ 06665 ║ hot chocolate ║ ? ║ 00011010 00001001 ║ ║ 07879 ║ service disk ║ 200 ║ 00011110 11000111 ║ ╚═════════╩══════════════════════════════════╩════════════╩═══════════════════╝
The service disk is used for cleaning, it makes hot water at 60° C flow straight through without any brewing time.
Using a barcode printer, I tried to modify the Coffe Créma barcode to give 300 ml (the max amount from the patent). I did some really extensive testing, printing out and feeding the machine a handful of barcodes, and it would seem there are six bits in the barcode, not four, that control the amount. The data is available here at Google Docs. The 6-bit range in question is in the middle: last 3 bits of the first byte and first 3 bits of the second byte (big-endian). Because Google Docs don't support in-cell colours, there is also a more nicely coloured Excel file uploaded here at Google Drive.
So I identified two 6-bit sequences that resulted in 300 ml for Crema.
For the sake of interest, I took one of the sequences and put it into the respective place of the original Espresso barcode. And there it is, I got 300 ml of Espresso.
While this was sort of a success (I'm now able to produce barcodes with correct volumes for the drinks I'm interested in), I'm still completely lost as of exactly how this works. As you can see from the experiment table, the pattern is rather fuzzy, and there are entries that give same volume from different combination of bits. I'm also not sure I'm getting the same brewing parameters with the barcodes I made.
Please share your ideas on how to understand this further.