Re: [PATCH v8 0/5] auxdisplay: add support for TI LP5812 4x3 Matrix LED driver

[Nam Tran]

On Wed, 30 Apr 2025 Pavel Machek wrote:

> > > > > Is it intended to be used as a 4x3 matrix, or is this just an internal
> > > > > wiring detail, and should it be exposed as 12 individual LEDs instead?
> > > > 
> > > > The 4×3 matrix is a real and fundamental aspect of the LP5812’s operation.
> > > > It is not just an internal wiring detail.
> > > > The device adopts a Time-Cross-Multiplexing (TCM) structure, where 4 output
> > > > pins control 12 LED dots individually through scanning. Each pin includes
> > > > both high-side and low-side drive circuits, meaning matrix multiplexing is
> > > > required for proper operation — it cannot be treated as 12 completely
> > > > independent LEDs.
> > > 
> > > Scanning is really a detail.
> > > 
> > > If this is used as rectangular 4x3 display, then it goes to auxdisplay.
> > > 
> > > If this is used as a power LED, SD activity LED, capslock and numlock
> > > ... placed randomly all around the device, then it goes LED subsystem.
> > 
> > The LP5812 is used for LED status indication in devices like smart speakers,
> > wearables, and routers, not as a structured rectangular display.
> 
> Well, IIRC it also supports automated animations, and that does not
> make sense on LED indicators. So... what device do _you_ have and how
> exactly is it used there?

We’re using the LP5812 in a battery-powered smart speaker as a status indicator
with visually enhanced lighting — for example, breathing effects during standby
and fading effects during voice processing.

While the LP5812 supports autonomous animations, they’re used here to offload
real-time brightness control from the main controller. Each LED’s animation engine
enables smooth transitions like fade-in/fade-out and breathing effects.
These patterns are configured once and run autonomously, saving MCU load and power,
while still serving traditional indicator roles.

Best regards,
Nam Tran