What is it?

This is a small (0.4 x 0.7 inches) breakout board with ISSI's IS31FL3194 three-channel led driver IC and a Lumex LX0404 rgb led.

From the datasheet: "IS31FL3194 is a 3-channel LED driver which features two-dimensional auto breathing mode. It has Pattern Mode and Current Level Mode for RGB lighting effects. The maximum output current can be adjusted in 4 levels (40mA Max.)."

The IS31FL3194 allows selection of maximum led current in four bands up to 40 mA (0 - 10, 0 - 20, 0 - 30 and 0 - 40 mA) and 256 steps in current output; this provides 16.8 million colors for the rgb led.

The board includes everything you need to develop and test programs for the IS31FL3194 including access to the device enable (pulled LOW by a 100 K resistor, so default disabled), I2C ports, and a high-quality, on-board rgb led. The board also exposes the three channels of output so you can connect your own led; the LX0404 can be disconnected by simply cutting the trace between the two solder pads on the front of the board.

Why did you make it?

RGB leds are great for indication but generally require the use of three dedicated MCU GPIOs, which can be a problem in applications where the number of GPIOs is limited. RGB leds are capable of displaying millions of colors but either require PWM for the GPIOs or resource-consuming calculations on the MCU host to manage the timing. Also, each led requires current limiting resitors adding to design complexity and making space-constrained designs a bit more difficult.

The IS31FL3194 allows multiple types of indication without tying up any extra GPIOs (assuming you are using the I2C port anyway for sensor control, which is usually the case for my applications) and the embedded ASIC does all of the timing/PWM calculations so the full range of colors as well as breathing, pulsing, and any other modes you can imagine and program become available for use in the application. The current is limited internally by the IS31FL3194 so no current limiting resitors for the rgb led are needed.

I wanted a simple breakout that I could use on the breadboard for program development and testing to see how this solution could be used in my projects. I found it easy to design since the circuit is very simple, and assembly was easy too despite the IS31FL3194's WLCSP. It was easy to get the device to work and ISSI was very responsive and helpful with the few questions I had. Kudos to ISSI!

What makes it special?

This is a small and inexpensive IC that offers the promise of sophisticated rgb led control for indication that reduces the burden on constrained MCU GPIOs, CPU resources, and board space. I wrote a simple sketch to test the leds and exercise one of the lighting modes found in the documentation for the IS31FL3194 evaluation kit.

Order the pcbs from OSH Park and assemble one yourself or order the fully assembled and tested board from me and see how easy it is to add sophisticated led indication to your project!

Here is a demo of the device in action: