Interface for multiple status leds

[ziggyfish]

Hi,

I am working on a system that will have about 28 power status LEDs, I want these LEDs to be on a separate daughter board.

What is the best way to manage this amount of connections?

Ideally I want these status signals on a I2C/SPI bus, so that a Microprocessor to process and monitor these signals.

Thanks

Brendan

[Doctorandus_P]

One way is to put a bunch of 74HC595 shift registers in series.

Another way is to use a microcontroller on both sides. uC's are a bit more expensive then shift registers, but you only need one of them, and you can combine it with scanning a matrix of LEDS, combine it with buttons, maybe a HD44780 or other stuff that's common on a front panel.


Then, there are all kinds of dedicated LED drivers. One of them is the MAX7219, which is a chip I do NOT like much. The "Maxim" variant is redicilously expensive, the clones from china are ... unreliable at best, and on top of that, the "dimmng" feature has far to few steps to be useful. On the plus side, this chip can handle a matrix of 8*8 = 64 LED's  A lot of the bigger shops have whole separate sections for LED drivers.

[ziggyfish]

Doctorandus, never thought about using shift registers.

It would work very well with the rest of the system, and is extendable.

Also I can put that signal into a microprocessor, do what I need to do.

I can then either send it to a matrix led driver IC, or if I want to go real fancy send it to a LCD display of some sort.

Thanks for the idea.

[JustMeHere]

Those RGB LED panels are driven by shift registers.  The library PxMatrix can drive them.  They are basically driven as a long string individual LEDs. (Ex:  64 x 64 x 3 ~ 12,300 LEDs)

So I can attest this will.work well.  PxMatrix drives it via SPI.  I get refresh rates over 700 frames per second.   My MCU is an esp32.   The 2 cores of the esp32 work well here.  One core is dedicated the refresh.  It reads from a frame buffer.  The other core does the actual work and "drawing".  This yields a very smooth screen experience.

I'd attach a video, but no joy with the format.

[tooki]

Another option (if you don’t need dimming) is generic port expander ICs. A couple of those and you’re set. (Using I2C.)

[MarkF]

The MCP23008 is an 8-bit expander with an I²C interface

The MCP23S08 is a 8-bit expander with a SPI interface