[FAQ] LP5860: How to master LP586x devices with LED matrix applications within five minutes?

Q1: Why are LP586x better solutions to drive Animated-Amounts-Autonomous (AAA) LEDs?

The LP586x devices are high-performance LED matrix drivers which support up to 198 LED dots or 66 RGB dots. In addition to the large quantities of LEDs, flexible Analog / PWM dimming options can accomplish a wide spectrum of applications with fancy animation effects. For more detailed specs comparison, please refer to the table below introducing our signature products in RGB LED family.

 Fig #1: Signature Products in RGB LED Portfolio

Q2: How to quickly set up the test environment for LP586x?

    1. Apply for a set of LP5860EVM board online 

        https://www.ti.com/tool/LP5860EVM?keyMatch=LP5860EVM

    2. Follow the instructions started from "#2 Hardware and Software Preparation" in the User Guide

    3. Visualize some pre-defined RGB lighting patterns for various customization

Q3: How to configurate PWM duty cycle and LED output current in the register panel to achieve PWM/Analog dimming respectively?

Analog dimming modifies the current gain control by three factors: global 3-bit Maximum Current (MC), 3 groups of 7-bit Color Current (CC), and individual 8-bit Dot Current (DC).

• Global 3-bit Maximum Current (MC): The MC sets the peak current value for every single LED dot. In the register map, it is composed of digit#1~digit#3 in Dev_config3 register. The default value of MC data is 011b=15mA.

• 3 groups of 7-bit Color Current (CC): The CC divides 18 current sinks into 3 color groups. In the register map, it is shown as R/G/B_current_set. The default value of all CC data is 0x40=50.4%.

• Individual 8-bits Dot Correction (DC): The DC controls each LED individually by using dot current function. In the register map, it is indicated as DC0~197. The default setting of DC data is 0x80=50.2%.

   Fig #2.1: Current Gain Calculation

PWM dimming adjusts the duty cycle determine the total lux emitted by three factors: PWM global, PWM group, and PWM individual.

• PWM global: The global PWM control function can regulate all LED dots at the same time. In the register map, it serves as the Master_bri register with a default value of 0xFF=100%.

• PWM group: 3 PWM groups are programmable for various duty cycle control. Users can create unique color patterns for the LEDs in a single PWM group by writing different register values. In the register map, LEDs can be selected into groups by Dot_grp_sel registers. The Group_bri registers set default PWM duty cycle as 0xFF=100%.

• PWM individual: The individual PWM register is 8-bit under data refresh mode#1 and mode#2, but 16-bit under mode#3. At mode#3 operation, the Enhanced Spectrum PWM (ES-PWM) algorithms achieve high refresh rate and avoid flicker issues. Compared with 8-bit PWM, 16-bit PWM enables ultimate high-resolution dimming in LED animation effects. In the register map, it represents as PWM_bri0~395 with a default value of 0x00.

  Fig #2.2: PWM Duty Cycle Calculation 

Q4: What are the differences between three data refresh modes in Device Configuration panel?

Mode #1: 8-bit PWM data without VSYNC (VSYNC button on LED CONTROL page is de-activated). Data is sent out instantly once received. In mode #1, you only need to refresh the single dot data instead of updating the whole SRAM. It is called “on demand data refresh” which saves the total data volume effectively.

Fig #3.1: Whole SRAM Data Refresh vs On Demand Data Refresh

Mode #2 / #3: 8-bit / 16-bit PWM data with VSYNC. A VSYNC signal is generated from external MCU and imported into LP586x. The data is held and sent out simultaneously by frame after receiving the VSYNC command. Different from Mode #1 operation, you need click the green VSYNC button to update data on the EVM board.

Compared with Mode #1, Mode #2 and Mode #3 provide a better synchronization due to the frame control when multiple LP586x devices are connected. The device holds the data and refresh the whole frame by a fixed frame rate – ƒ_VSYNC (24Hz, 50Hz, 50Hz, 120Hz) – or even higher to achieve more vivid animation effects.

Fig #3.2: Data Refresh Mode 

Q5: How to implement the separate control of LED brightness and color temperature within flexible dimming options?

PWM dimming is a good choice for brightness control (BRC). On the Brightness Settings panel, the color temperature is determined by the RGB proportion – selecting from the color wheel or writing hex values into registers. The Brightness Percent slide bar adjusts BRC with a fixed proportion of PWM duty to avoid changing color temperature.

Fig #4.1: LED Brightness Settings Panel

Analog dimming is an alternative for flexible color temperature control. On the LED Dot Correction panel, the RGB current gain is set by equivalent default values. For example, if you increase the dot current on R#, the chosen LED will appear more reddish. DC0~197 registers enable the single-dot control and produce unique color combinations.

Fig #4.2: LED Dot Correction Panel

Q6: Could you provide some relevant resources for LP586x? 

• OFFICIAL USER GUIDE: LP5860EVM User Guide

• MOST RECENT GUI SOFTWARE: LP586x GUI v0.6.0

• CCS SAMPLE CODE BASED ON MSP432 MCU: LP586x_Samplecode_MSP432P401R.zip

• TIDA xxx KEYBOARD PROMO VIDEO: LP5860 Keyboard Demo Video 

• TIDA xxx MINI-DISPLAY PROMO VIDEO: LP5860 Mini-Display Demo Video

• To be updated :)