How to auto generate barcodes for Entity Registration in Drupal 7 I read this article about using rules and a trigger to populate/create a barcode field from a serial field, tried toy follow it but the screens/ facilities of Drupal 6 seem different for v 7 and the documented steps cannot be replicated. In particular I expected barcodes to be part of the drop down for fields but it isn't

"basically you should add a new rule that fills for you the barcode when new content is created starting from the serial field. The steps are:

create a new rule
trigger it on the event: 'after new content is saved'
set some condition on the type of the content (optional)
use 'populate a field' (under CCK category) as action
choose your barcode CCK field
Use the token of your serial field : [node:field_YOUR_TOC_SERIAL_FIELD-id] -- I don't remember why I didn't use the token but the follow php code:

 array('barcode' => [node:field_MY_FIELD_NAME-id]));
?>
If you didn't use Rules before have a look here: http://dev.nodeone.se/node/646  "
Its complicated but I essentially ended up using the available barcode online generators (Google has an online QR Code generator) and then embedding the URL in HTML mail that I was sending out.