To achieve vivid lighting patterns, the high-speed communication interface between the host microcontroller with the LED driver is very important. Let's dive into the basics of RGB communication interfaces.

So how exactly do you select an LED driver interface? Usually, there's three key aspects to think about-- applications, controller resources, and some other considerations. For applications, there are some common requirements which result in some common preferences.

For example, I2C is widespread in personal electronics, like smart speakers and gaming keyboards. While SPI is typically used in industrial applications, such as LED display and programmable water controllers within factory environments. There are also some applications, like architectural illumination, which uses LED stripes. In those cases, a single wire interface is needed.

You also need to consider the controller resources. You may have eyes I2C, SPI, or GPIO in your system, so you should use the interface accordingly.

There are also some other restrictions, though. For example, if you need to use a lot of LED drivers in cascading to drive the right amount of LEDs, then you need to use SPI interface. Sometimes you might be using smaller flex PCBs which require less wires, so a single wire interface might be more suitable.

So what's the difference between all of these interfaces? I2C uses two wires to control LED drivers and the data transfer rate is lower than 1 megahertz. It can also use multiple drivers together in parallel.

For SPI, the data transfer rate is much higher, up to 35 megahertz. SPI is suitable for applications requiring high-speed data transfer rates. In this scenario, you should use multiple LED drivers in a cascade to drive your total LEDs or LED arrays. Since the data transfer rate is high, large quantities of LED drivers can be used together.

Single wire interface targets applications which require multiple LED drivers in cascading and long signals wires that need to avoid data losses. The maximum data transfer rate for single wire interface is 3 megahertz.

Now let's look at I2C interface. As you can see from the block diagram, two LED drivers are driven by a controller through I2C interface in parallel. There are two wires, that are SDA and SCL. SDA is used for data, while SCL is used for clock. Addresses are used to distinguish different drivers.

There are three types of I2C interfaces according to their maximum SDA frequency. The standard one supports up to 100 kilohertz, and fast mode I2C supports up to 400 kilohertz. The fast plus mode I2C can support the fastest frequency, up to 1 megahertz.

There are two ways to drive multiple LED drivers. One is using an I2C address for each driver and controlling them one by one. For example, you can use address 1 to control the first driver, then address 2 for the second one, then address 3 for the third one.

You can also use the broadcast address to control all of the drivers together. For example, you may want to control all the drivers together in the same way, so using a broadcast address will ensure all the drivers respond together.

Now you're seeing the block diagram of serial interface that uses cascading topology to control multiple LED drivers asynchronously. This serial interface includes two to five wires regarding different protocols.

For example, the block diagram shows an interface with four wires. SN is used for data input and SCLK is used in comparison with SN to shift the data into the driver. LAT is used for latching the data into the driver's internal registers. And GCLK is a clock reference for output PWM signals. For drivers with an internal oscillator, GCLK is not necessary.

In short, the cascading topology supports multiple devices used synchronously, and up to 35 megahertz data transfer rate can achieve high refresh rates. Serial interfaces are also suitable to drive time-multiplexing matrix displays. We will cover those details in section 5 of this training series.

Finally, just as its name implies, single wire interface uses one wire to communicate with the host. Your driver has SDI for data input and SDO for output to the next driver, so there won't be long signal wires from the controller. To make sure there are no data losses, an internal buffer is used. This makes it possible to connect unlimited devices in a series.

And another aspect, a single wire interface reduces wire costs and communication failure, making it a great option for applications using long LED stripe. Now that we have reviewed how to select the right LED driver interface, we hope you can take this back to your RGB projects. We hope you learned something valuable today. Consider watching the next video in our series to learn about RGB LED powers consideration.