pos/pos_customer_display/readme/USAGE.rst

Once everything is configured, just start the POS as usual. You will see messages on the device when:

* you start the POS,
* you add or remove a product,
* you select or deselect a customer,
* you press the Payment button: the device will display the total amount,
* you enter the amount of cash you receive: the device will display the amount of the change to give back,
* you validate an order and go to the next customer,
* you close the POS.