InetrfaceProducts NXP / PCA995xA

PCA9955A and PCA9956A class library. The PCA9955A is a 16-channel and the PCA9956A is a 24-channel Fm+ I2C-bus 57mA/20V constant current LED driver. The PCA9955A has a extended feature which called "Gradation control".

Dependencies:   CompLedDvrCC

Dependents:   PCA9956A_Hello pca9956b_two_demoboards PCA9955A_Gradation_control PCA9955A_Gradation_control ... more

What is this?

Code for PCA9956A and PCA9955A.
24-channel and 16-channel constant current type LED driver component class.

Please refer to the component page for details

Components / PCA9955B, PCA9956B : 16 & 24-channel constant current LED driver

PCA9955B and PCA9956B are I²C-bus controlled 16-channel constant current LED driver optimized for dimming and blinking.

#include "mbed.h"
#include "PCA9956A.h"

PCA9956A    led_cntlr( p28, p27, 0xC4 );  //  SDA, SCL, Slave_address(option)
LedPwmOutCC led( led_cntlr, L0 );

int main()
{
    while( 1 ) {
        for( float p = 0.0f; p < 1.0f; p += 0.1f ) {
            led     = p;
            wait( 0.1 );
        }
    }
}

About the chips

PCA9956A

The PCA9956A is an I²C-bus controlled 24-channel constant current LED driver optimized for dimming and blinking 57 mA LEDs. Each LED output has its own 8-bit resolution (256 steps) fixed frequency individual PWM controller that operates at 31.25 kHz with a duty cycle that is adjustable from 0 % to 99.6 % to allow the LED to be set to a specific brightness value.

Datasheet: http://www.nxp.com/documents/data_sheet/PCA9956A.pdf

PCA9955A

The PCA9955A is an I²C-bus controlled 16-channel constant current LED driver optimized for dimming and blinking 57 mA Red/Green/Blue/Amber (RGBA) LEDs in amusement products. Each LED output has its own 8-bit resolution (256 steps) fixed frequency individual PWM controller that operates at 31.25 kHz with a duty cycle that is adjustable from 0 % to 100 % to allow the LED to be set to a specific brightness value.

On addition to this, the PCA9955A has "Gradation control".
The gradation control is a new feature of PCA995xA series. After the register setting and start the control, the PCA9955A performs dimming cycles automatically without MCU intervention.

Datasheet: http://www.nxp.com/documents/data_sheet/PCA9955A.pdf

PCA9952 and PCA9955 (non-A version)

The PCA9955 and PCA9955 (no-A at end of the type number) is not supported by this component class.

How the API works?

When the instance is made, all set up for PWM operation are done automatically.
For the operation, user can control the LED brightness in two ways.

• PWM
• Current

PCA9955A and PCA9956A have internal 31.25kHz oscillator to generate internal PWM waveform. This signal switchs the output current ON and OFF. The class' function pwm() controls duty-cycle of this output.

Another control is current. Since the PCA9955A and PCA9956A are constant current type LED driver, those have internal current sources. The current source on each channels has independent control of output current. The class' function current() provides interface to current change.

Tips for the chips

#include "mbed.h"
 
#include "PCA9955A.h"
#include "PCA9956A.h"

PCA9955A    led0( p28, p27, 0xC0 );    //  SDA, SCL, Slave_address=0xC0 (16-channel chip)
PCA9956A    led1( p28, p27, 0xC2 );    //  SDA, SCL, Slave_address=0xC2 (24-channel chip)
 
int main()
{
    led0.current( ALLPORTS, 1.0 ); //  Set all ports output current 100%
    led1.current( ALLPORTS, 1.0 ); //  Set all ports output current 100%

    led0.pwm( ....    //  PWM control for PCA9955A(16-channel chip)
    led1.pwm( ....    //  PWM control for PCA9956A(24-channel chip)
    ...

Other sample code

For PCA9955A : http://developer.mbed.org/users/nxp_ip/code/PCA9955A_Hello/
For PCA9956A : http://developer.mbed.org/users/nxp_ip/code/PCA9956A_Hello/
For Gradation control of PCA9955A http://developer.mbed.org/users/nxp_ip/code/PCA9955A_Gradation_control/

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