Issues (in order of difficulty):
1. Identify main board for the Media box unit
The board should:
- be compatible with USB host shield, or be able to act as a USB host - Due is the only board for the latter option
- be able to appear as a native keyboard (32U4 or SAMD microprocessor boards) - Leonardo, Esplora, Zero, Due and MKR Family
- be compatible with HX711 (or similar) load sensor modules
- work with RFID module
- not break the bank as there are going to be a number of Media boxes per setting
- be as small as possible as space is at premium at some of the settings
Key deliverable here is fast process where Media box should:
- using a barcode scanner scan a barcode on CD/DVD case
- for each scanned product - read load sensor to count number of discs (Q) placed onto Media box disc holder - discs weigh 16g each so it should be achievable
- write barcode and Q onto NFC sticker attached to the Media box
- via Keyboard.write() pass barcode to laptop/pc where EPOS system runs
- update crystal display at each stage until scanning is complete
2. Identify main board for the Main unit.
Here a fairly standard board should be sufficient such as UNO - may be Due as speed is more crucial for the Main unit. Main unit carries out a 10 or so step process to archive discs without cases. These steps involve reading NFC data, activating steppers/servos and updating crystal display - so nothing out of ordinary.
I started on (1) but got stuck in implementation of software USB keyboard simulation using V-USB. Another option was to go through amending bootloader program as explained in HID Project, but it seemed too much to go through for a novice like me.