Difference between DMX and SPI
March 15, 2020
The IC of DMX is with Differential Signal ( like signal transferring in net cable)
Differential signaling: a method of transmitting information electrically with two complementary signals sent on two paired wires, called a differential pair. Since external interference tend to affect both wires together, and information is sent only by the difference between the wires, the technique improves resistance to electromagnetic noise compared with use of only one wire and an un-paired reference (ground). The technique can be used for both analog signaling, as in balanced audio, and digital signaling, as in RS-422, RS-485, Ethernet over twisted pair, PCI Express and USB. The opposite technique is called single-ended signaling. Differential pairs are usually found on a printed circuit board, in cables (twisted-pair cables, ribbon cables), and in connectors.
The IC of SPI is with TTL Signaling ( Transistor–transistor logic )
TTL: Transistor–transistor logic (TTL) is a class of digital circuits built from bipolar junction transistors (BJT) and resistors. It is called transistor–transistor logic because both the logic gating function (e.g., AND) and the amplifying function are performed by transistors (contrast with RTL and DTL) .
Let’s make it simple,
if the chip is with differential signaling, the distance between every 2 pixels can reach hundreds of meter. And the signal still remains stable, the lighting effect of these 2 lights will be the same.
While the chip is with TTL signaling, the longest distance between every 2 lights is 10m, and it is quite easy affected by other signals, like TV, Radio, Mobile, etc. In this case, we will advise our clients to select a short pitch ( distance between every 2 lights, the best way is less than 100cm, or even less than 50cm).
