What is the origin of Chinese writing?

From Wikipedia --

Legendary origins

According to legend, Chinese characters were invented by Cangjie (c. 2650 BC), a bureaucrat under the legendary Yellow Emperor. There are quite a few variations of the legend. One of them tells that Cangjie was hunting on Mount Yangxu in modern Shanxi when he saw a tortoise whose veins caught his curiosity. Inspired by the possibility of a logical relation of those veins, he studied the animals of the world, the landscape of the earth, and the stars in the sky, and invented a symbolic system called zì — the first Chinese characters. It was said that on the day the characters were born, Chinese heard the devil mourning and saw crops falling like rain, as it marked a second beginning of the world.