RoseOnRails – LEDs and Rails

Yesterday night, Alexis managed to control the LEDs with a STM32 discovery.
We then pierced a rails segment and stuck the strip under it to see how it all worked out !

In fact, it was quite easy to have the strips fit under the railway, and the result is mesmerising … see for yourselves!

However, the way the LEDs were controlled for this test, does not enable us to have other threads in our programme because we need a quite precise timing to send information to the LEDs strips.

What we will do is :
Transfer our data (LEDs colors) to the external port of our development board through DMA and send the information from the board to the LEDs strips thank to SPI.

RoseOnRails – Guess what we received !

Hi everyone,

We finally received our thirty one-meter LED  strips!!
I am going to start playing with them tomorrow !


RoseOnRails – LEDs everywhere!


On Friday, I found an interesting LED strip which is called Neopixel and is sold by Adafruit. This LED strip seemed to be exactly what we were looking for: a strip of addressable LEDs individually controlled by a PCB which can be modulated through the use of  a 8 bit PWM … However, as we  need 28 meters, 17$ a meter seemed somehow expensive!

I then looked up for LED strips on aliexpress and alibaba and found out that there were mainly 3 types of LED strips. The LEDs in those LEDs strips can be controlled bu PCBs such as : WS2811, WS2812/WS2812b or LPD8806.

The LPD8806 controllers are poorly documented (it is very hard indeed to find proper information concerning timing constraints in the datasheet) and after having navigated on various forums, notably on the adafruit forum, it seems that the timing for LPD8806 is somehow hard to control, and thus the PWM and the LED colours are hard to control.

The WS2811 are 6 pins controllers for LEDs, seem easy to use and are well documented. Though very interesting, the WS2812 and WS2812b provide better performances (more powerful LEDs), with fewer pins (only four) and are easier to find on the internet. WS2812b is merely an enhanced version of WS2812 and provides mainly mechanical improvements to the IC.

In the light of the above, we have decided to use ws2812b LED controllers.
We will run some tests to see if it is possible to locate the trains thank to the LEDs, as soon as we receive our first meter of LEDs strip!