RC filter for serial comm, placed near the transmitter or the receiver?

[jnz]

I have a small device that takes in single line usart wire for data in.

The datasheet calls for an RC filter, the values I'm on my own to figure out.

I'm pretty sure that I want the RC filter placed close to the transmitter, but I don't know if that's right or why.

Thoughts?

[ledtester]

What's the device? Can you post the datasheet?

[jnz]

In this case, a Lumex embedded IC LED.

Accepts a waveform that you can make with SPI or UART or bit bang.

https://www.lumex.com/news/SMD-LX0707RGB-TR.html

[ledtester]

That module looks very much like the WS2812B smart leds.

With the WS2812B a ~400R resistor is recommended between the MCU output pin and the first led in the chain especially if there is a significant amount of wire between the two. See, for instance, this discussion:

https://forum.arduino.cc/t/arduino-ws2812b-data-pin-resistor/533031


Update: According to these sources the resistor should be placed near the LED:

https://electronics.stackexchange.com/a/353581/95488

https://learn.adafruit.com/adafruit-neopixel-uberguide/best-practices#:~:text=Place%20a%20300%20to%20500%20Ohm%20resistor%20between%20the%20Arduino%20data%20output%20pin%20and%20the%20input%20to%20the%20first%20NeoPixel