Vending Machine/Cashless Device Implementation
There is a board between the Nanode (see Media:VMC-Nanode Schematic.png) and the vending machine which both powers the nanode from the ~34vdc supply, and allows serial communication with the VMC.
The nanode is connected (using software serial) to an RFID reader mounted under the 'H' logo on the outside of the Vending machine. There is also a micro-switch attached to the coin-reject mechanism (to allow any RFID card read to be cleared from memory), and a blue LED above the reader to indicate when a card has been read & recognised.
To keep things simple, the UDP/IP interface to holly is text based; the sequence of messages is shown in the flowchart below:
Sent when RFID card first read
Sent in response to AUTH if the card is known & marked as active in the database.
Sent in reply to AUTH if the card is either not know, or marked as expired/canceled.
Sent when a selection is keyed in. <amount> is in pence.
Sent in response to VREQ if the purchase is permitted (e.g. credit limit won't be exceeded).
Sent in response to VREQ is the vend should be denied for any reason.
Sent after the VMC reports to the nanode that the product has been successfully vended.
Sent if the VMC reports that the vend failed. ***UNTESTED***. Not sure if our vending machine can/would ever report a failed vend.
Sent if the coin reject button is pressed. Will record a cancelled vend if an AUTH has been sent, but no VREQ yet received - otherwise it has no effect.
Information message that can be sent at any stage - has no effect other than being written to a log on holly.
|<RFID serial>||RFID serial number - expected to be 9 digits long|
|<transaction number>||Unique number assigned to the vending machine transaction when an |
|<position>||Position in the vending machine as reported by the VMC. Note that this location is mapped to the locations codes displayed in the vending by holly (e.g. 41-31 reported here corresponds to location A1).|