KhadashPay is my attempt to build a payment system from scratch.
KhadashPay Firebase Edition's page on SourceForge: https://sourceforge.net/projects/khadashpay-firebase-edition/
Tutorials:
V1.0:
https://www.instructables.com/DIY-IoT-Payment-System-With-Google-Firebase/
https://medium.com/@Northstrix/diy-iot-payment-system-with-google-firebase-ff92ccea1245
https://www.hackster.io/northstrix/diy-iot-payment-system-with-google-firebase-khadashpay-68c070