Automotive Tail Light Solution based on STM ALED1262ZT

STEVAL-LLL002M1

The STEVAL-LLL002M1 is an LED array driver system board that features local dimming and diagnostic capabilities for automotive applications. It is based on the ALED1262ZT 12-channel LED driver controlled via the I²C interface by the STM8AF6266 microcontroller. Four ALED1262ZT LED drivers drive a matrix of 48 red LEDs. 

The onboard A7986A DC-DC converter accepts standard adapter input voltage with reverse polarity protection to provide voltage and power for the circuit board operation.

The STEVAL-LLL002V1 kit includes jumpers to simulate LED open-circuit faults, and a 4-pin SWIM connector for debugging and developing the STM8AF6266 microcontroller firmware. 

The kit can operate in bus-driven mode (BDM), standalone mode (SAM), and GUI mode. In bus-driven mode, the circuit board is controlled via onboard buttons and potentiometers. 

Commands for the ALM1262ZT driver are sent by the STM8A microcontroller through the I²C bus.

The STSW-LLL002FW firmware implements configuration and control of the ALED1262ZT LED driver through the I²C interface, based on the 8-bit automotive-grade STM8AF6266 microcontroller. 

This firmware is specifically designed for the STEVAL-LLL002V1 evaluation kit to demonstrate the functionality of the ALED1262ZT for application development of automotive tail lights with pattern animations.

The embedded GUI (STSW-LLL002GUI) allows control of buttons, read/write configuration registers and individual channel brightness, as well as programming up to 20 LED modes with variable transition speeds or using four pre-configured modes.

In standalone mode, the STEVAL-LLL002V1 evaluation kit operates independently without MCU control, and you can select between two possible output configurations using the OTP½SPDT switch (SW2).

In GUI mode, the circuit board is connected to a PC via a USB-UART bridge, and you can observe and control various functions of the driver through the graphical user interface.

The PC application provides a graphical interface for controlling a 4x12 LED lighting array and monitoring the fault detection capabilities of the STEVAL-LLL002V1 evaluation kit, which is designed to represent rear automotive LED lighting applications and features the STM8AF6266 microcontroller and four ALED1262ZT automotive-grade LED drivers. 

Once the STEVAL-LLL002V1 array board and UART bridge are correctly connected, the GUI quickly establishes a connection and provides 12-24VD.

Key Features

Automatic port selection and board recognition.

Basic Mode.

Enable or disable hardware buttons.

Driver error detection and visualization.

Collective and individual LED switch toggling.

Read and write configuration registers.

Advanced Mode: Individual channel brightness control.

Framework programming

On-board programming of up to 4 preset animation modes.

Design and preview custom animation modes.

Set frame rates and delays.

The GUI provides an interface to perform basic and advanced mode control of any or all 48 red LEDs on the array board using a separate interface. It also offers a dedicated third interface for designing and recording custom animations and modes that can be downloaded and executed on the LED driver array board later.

Scenario Application Diagram

Display Board 

Program Block Diagram

Core Technical Advantages

Specifically designed for automotive applications.

7-bit PWM local dimming.

Slow start-up/shut-down time with gradual output delay to reduce EMI.

Error detection for open-circuit LEDs.

Thermal shutdown and over-temperature alert.

Independent and bus-driven modes.

400 kHz fast I²C interface with optional extended Hamming code.

These core technical advantages highlight the design focus on automotive applications, efficient dimming capabilities, EMI reduction, LED fault detection, thermal protection, and flexible control modes.

Solution Specifications

Various pre-configured and programmable patterns on a 12x4 red LED matrix.

7-bit PWM local dimming control with non-linear step adjustment for perceived brightness by the human eye.

Speed control for pattern transitions.

Mode switching via button press.

Safety standalone mode functionality and OTP pre-programming mode for customized configurations.

Fast I²C interface with optional extended Hamming code.

Open error simulation and real-time detection.

12V to 24V DC power supply with reverse polarity protection.

GUI for advanced driver configuration.

USB-UART bridge for PC connection (STEVAL-LLL002D1).

Compliant with RoHS and WEEE standards.