This paper presents a new type of digital signal method and algorithm for embedded systems including mobile phones and other handheld devices. A digital communication method is suggested for mobile phone and embedded devices using screen light signal of devices which contain data such as game item, payment information, personal information, etc. The new method provides an economic and efficient solution to mobile networking environment. We studied the solutions focusing on payment system by updating embedded software without need of additional hardware modules to mobile devices. The solutions can be used also for digital item movement between mobile phones or game devices.