LED Driver 8 Click

How does it work?

LED Driver 8 Click is based on the PCA9957, a daisy-chain SPI compatible 4-wire serial bus controlled 24-channel constant current LED driver optimized for dimming and blinking 32 mA RGBA LEDs from NXP Semiconductors. The PCA9957 has 24 internal 8-bit DACs with an operating frequency of 31.25 kHz and a duty cycle from 0% to 100% used to adjust brightness levels for each LED current source. Each LED output is programmable and can be turned off, on (with no PWM control), set at its individual PWM controller value, or both individual and group PWM controller values. Its output peak current is adjustable with an 8-bit linear DAC from 125 μA to 31.875 mA because of the R4 resistor of 2kΩ connected to the REXT pin.

Gradation control for all current sources is achieved through serial interface and allows the user to ramp current automatically without any help from the MCU. It has two operation modes for each group: Single-Shot Mode (output pattern once) and Continuous Mode (output pattern repeat). Each channel can be set to either Gradation Mode or Normal Mode and assigned to any one of six gradation control groups. These groups have four independent registers to control ramp-up and ramp-down rate, step time, hold ON/OFF time, and final hold ON output current.

The LED Driver 8 Click communicates with MCU through a daisy-chain SPI compatible 4-wire serial interface with a clock frequency up to 10 MHz. The input labeled as OE routed to the PWM pin on the mikroBUS™ blinks all the LED outputs and can be used to externally PWM the outputs, which is useful when multiple devices need to be dimmed or blinked together without using software control. The PCA9957 also has a short load and overtemperature detection circuitry, thermal shutdown feature which protects the device when the internal junction temperature exceeds the factory-defined limit, and a Reset function routed to the RST pin on the mikroBUS™ which is activated by sending an active low input on this pin with a minimum pulse width of 2.5μs.

This Click board™ is designed to be operated with both 3.3V and 5V logic voltage levels that can be selected via VCC SEL jumper. This allows for both 3.3V and 5V capable MCUs to use the SPI communication lines properly.

Specifications

Pinout diagram

This table shows how the pinout on LED Driver 8 Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	OE	Output Enable
Reset	RST	2	RST	INT	15	NC
SPI Chip Select	CS	3	CS	RX	14	NC
SPI Clock	SCK	4	SCK	TX	13	NC
SPI Data OUT	SDO	5	MISO	SCL	12	NC
SPI Data IN	SDI	6	MOSI	SDA	11	NC
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

LED Driver 8 Click electrical specifications

Software Support

We provide a library for the Led Driver 8 Click on our LibStock page, as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Library Description

The library contains a basic functions for using LED Driver 8 click.

Key functions:

• void leddriver8_set_mode_register( uint8_t mode_1, uint8_t mode_2 ) – Function for set mode registers
• void leddriver8_set_output_gain ( uint8_t num_led, uint8_t value ) – Functions for set output gain
• void leddriver8_set_brightness ( uint8_t num_led, uint8_t value ) – Functions for set Brightness

Examples description

The application is composed of three sections :

• System Initialization – Initialization SPI module and all necessary GPIO pins
• Application Initialization – Initialization driver init and sets module for working
• Application Task – Changes brightness on all LEDs. Controls are blinking on one LED.

void application_task ( )
{
    uint8_t cnt;
    for( cnt = 0; cnt < 0xFF; cnt++ )
    {
        leddriver8_set_brightness( LEDDRIVER8_BRIGHTNESS_ALL_LED, cnt );
        Delay_ms( 15 );
    }
    
    for( cnt = 0; cnt < 5; cnt++ )
    {
       leddriver8_set_brightness( LEDDRIVER8_LED_0, 200 );
       Delay_ms( 1000 );
       leddriver8_set_brightness( LEDDRIVER8_LED_0, 0 );
       Delay_ms( 1000 );
    }
}

The full application code, and ready to use projects can be found on our LibStock page.

Other mikroE Libraries used in the example:

• SPI Library

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.