Room77: Instant Calculator

[rootzoll]

A nice to have feature would be: While the user is putting in an amount the math operations of the keyboard are allowed to assist bar tenders in making the bill ... like: 2.50 x 3 + 8,80 and when pressed the invoice button the calculation gets resolved into a final price.

[arcbtc]

M5StackSats takes the current market choices of PoS card terminals and replicates them for bitcoin. The usual workflow is the amount is calculated on a till, then inputted into the card machine. Adding this functionality might introduce a layer of complexity different from what the typical hospitality employee is used to?

[hikaman]

I've open a PR #29
From my perspective the calculator add some functionality without complexity. Some usability tests would be nice. @rootzoll @arcbtc