led strip studio logo

What is the difference between SPI & DMX?

Quite often people ask us – “What is the difference between DMX and SPI?”. The simple technical answer is – both are communication protocols used to control LED strips. Simple analog RGB LED strips are typically controlled by DMX protocol, while SPI is used to control pixel LED strips (also called addressable or digital LED strips).

What is the DMX protocol?

DMX protocol is often called also DMX512. It stands for Digital Multiplex with 512 pieces of information.

DMX protocol is used to control lights used on stages, in bars or clubs. It’s simple protocol which transfers total of 512 values around 40-times per second. Every value is called channel and every channel contains value from 0 to 255. Every channel can be assigned to different function of the intelligent lighting – e.g. you can control Pan and Tilt using channels 1 and 2.

One DMX line transferring 512 channels is often also called DMX Universe. And quite often LED installations are using multiple DMX universes.

Simple analog RGB strips are typically controlled by DMX. You can control intensity of red, green, and blue color separately for whole RGB strip. That’s why one RGB strip requires 3 DMX channels (Red, Green and Blue) to be controlled.

Since DMX protocol transfers 512 channels, you can control up to 512/3 = 170 RGB LED strips using one DMX line.

512 channels of DMX – is that enough?

Well as you can probably figure out, the 512 channels is not enough. At least for most pixel LED installations. Yes, you can use several DMX universes. But every DMX universe is typically transferred over separate data cable. That requires a lot of cables if you want to use many RGB LED pixels.

What is the SPI protocol?

SPI stands for Serial Peripheral Interface and basically it allows you to transfer any kind of data. The SPI protocol is typically used to control addressable (or pixel) LED strips, because it allows transfer of more than 512 values. Typical SPI protocol used for addressable LED strips can control even 1000 individual RGB LED pixels.

Sometimes, the DMX is used instead of SPI to control pixel LEDs. If you would want to use DMX instead of SPI, you would need at least 6 DMX universes. Why 6? If you want to control 1000 RGB LED pixels, that’s total of 1000*3=3000 channels.

One DMX universe can control up to 512 channels, thus you need 3000/512=5.85 (round to 6) DMX universes.

Problems with SPI "standard"

As you can see, SPI protocol is more suitable to control RGB LED pixels used in addressable LED strips. There is an issue though with SPI – there is no standard protocol to control pixel LEDs. You probably heard already about WS2811 or TM1914 LED strips. These are different SPI protocols used to control pixel LEDs. That’s why you must set correct SPI protocol for your pixel LED strip you’ve purchased for your installation.

There is also more confusion for the SPI communication – same protocol may have different names. For example WS2811 is the same as TM1809 or even APA102. But e.g. APA102 Super LED is not compatible with WS2811. It is a mess indeed…

What are the differences between SPI & DMX?

Here is a little table summarizing the differences between DMX and SPI protocol

300m long cable
Recommended <1M *
3 wires (DMX+, DMX-, GND)
2 wires (Data, GND)
250kbps (slow)
>800kbps (much faster)
Unlimited **
Different protocols
* Can be improved with additional hardware e.g. The Symmetrizer
** Depends on your SPI line speed
Led Strip Studio logo

Recent Posts


Join more than 5000+ subscribers

Get the latest news and special offers

[mc4wp_form id="230"]