LED matrix is a great way of displaying either text pr graphical messages. The more dots you have – the more freedom you get. In other hand when number of dots increases, you got to think about easy way of sending messages to it.
lucadentella decided to go with Bluetooth option. He assembled Arduino circuit on the bottom of LED matrix which is driven by HC1632C controller. Arduino takes care of receiving Bluetooth messages from HC-05 Bluetooth module. Special care was taken on powering the thing. First of all he added LiPo battery charging and monitoring circuit. Then another circuit is used to rice LiPo battery voltage to 5V. Arduino accepts simple Bluetooth messages using basic protocol, so any device like Android smartphone can be used to send data.