PCAL6524HE functionality

[Rajender]

Hi,

We would like to use PCAL6524HE GPIO expander in our design. and we would like to understand exact functionality. Please help us in understanding the same.

1. How the LED can be controlled with GPIO expander? VCC is 3.3V and LED will be supplied with 5V and we want to understand how the LED can be turned on or off? it the Port output going to drive it or how?

2. Can all the 24 GPIOs be set or reset at a time? if not how may GPIOs can be set or reset at one time?

Thanks

[JozefKozon]

Hi Rajender,

1. How the LED can be controlled with GPIO expander? VCC is 3.3V and LED will be supplied with 5V and we want to understand how the LED can be turned on or off? it the Port output going to drive it or how?

[A] The GPIO pins can be set as inputs or outputs in the registers and also internal pull-up and pull-down resistors can be enabled and disabled for individual GPIO pins, thus bringing voltage to the GPIO pin or if pull-down is activated, connecting the pin to GND through the pull-down resistor. 

2. Can all the 24 GPIOs be set or reset at a time? if not how may GPIOs can be set or reset at one time?

[A] If the PCAL6524 is reseted, all the registers will be set to default values. Please check the Table 6. in the PCAL6524 datasheet for the registers default values.

Although the PCAL6524 can be used to drive LEDs, we have a range of LED drivers specifically designed to drive the LED diodes. I would rather recommend you one of our LED drivers for your application. Please see this link for a list of our LED drivers portfolio.

It would be much easier to use a LED driver to drive LED diodes, there are some code examples created and the LED drivers have functions specifically designed for LED driving. (Dimming, blinking, gradation control, etc.).

With Best Regards,

Jozef

[Rajender]

Hi Jozef,

Thanks for your reply!

Suggested parts look good to drive the LEDs. But we need a part only to turn LED on or off with fixed current. We don't need any other dimming functionality.

2. Can all the 24 GPIOs be set or reset at a time? if not how may GPIOs can be set or reset at one time?

[A] If the PCAL6524 is reseted, all the registers will be set to default values. Please check the Table 6. in the PCAL6524 datasheet for the registers default values.

[Q] My question is, can we access all 24 GPIO simultaneously i.e., can we turn all the LEDs turn on or off at a time or can we access them only serially? please clarify this for both parts i.e., GPIO expander and LED driver ICs.

Regards,

Rajender.

[JozefKozon]

Hi Rajender,

[Q] My question is, can we access all 24 GPIO simultaneously i.e., can we turn all the LEDs turn on or off at a time or can we access them only serially? please clarify this for both parts i.e., GPIO expander and LED driver ICs.

[A] If you need to only turn off and turn on all of the 24 GPIO simultaneously, it is possible with both the PCAL6524HE GPIO expander and also with our LED drivers. 

In the PCAL6524HE all the GPIO are set as inputs. You can set them as outputs with the autoincrement function by the registers configuration port registers, thus turning on the LEDs.

In the same registers you can set the ports to high-impedance input, thus turning off the LEDs. 

Similar way you can turn on and turn off the LEDs in our LED drivers with the auto-increment function if I2C interface is used or if SPI interface is used, all the registers can be written in one loop. On top of software control, the LED drivers have OE! pin, which can be used to turn on or turn off all the outputs at the same time, without using software control. 

Please refer to section 1. in the PCA9956B datasheet.

With Best Regards,

Jozef