Where the chain ends
The fifth LED's output is soldered to a pad that no trace reaches, so the data stops on this board. A second bar cannot be chained after this one, whatever its back says. Two bars need two GPIOs, or one GPIO and the same colours on both.
LED5's output goes nowhere
In the net list, the DATA pin goes to LED1's input, and each LED's output goes to the next one's input. LED5's output is on a net with nothing else in it: the pad at the LED's corner, and no trace, via, pin or hole.
So whatever reaches LED5 after its own 24 bits is sent into that pad and lost. The board has no way to hand data on. A second bar cannot be chained after this one, and the line printed on the back that says otherwise is wrong.
Two bars, three ways to wire them
After the first: there is nothing to wire to. A sketch that sends ten colours lights five, and the second bar stays dark.
On its own pin: the second bar's DATA on a second GPIO, and two strip objects in the sketch, five LEDs each. Each bar gets its own colours. This is the way to drive ten different LEDs.
On the same pin: both DATA pins on one GPIO. Each bar's LED1 hears the same frame, so both show the same five colours. Useful for a mirror, and for nothing else.
Tell the library five
A strip object's LED count is the number of colours it sends. On this bar the right number is 5. More is not an error, just wasted time and a promise the board cannot keep; fewer leaves the bottom LEDs with whatever they had last.
When it does not work
That is all there is to light. The library sends ten colours; the five LEDs keep the first five, and the other 120 bits leave LED5's output onto a pad that goes nowhere. Set the count to 5. For ten LEDs, put a second bar on its own pin and give it its own strip object.
Not in any way the board was designed for. The pad is at the LED's corner, with no trace, via or hole to reach it, and heating a 5050 LED on a finished board risks the LED. Two bars on two pins does the same job with no soldering.
Yes, on short wires. One GPIO can drive two LED inputs; each bar's LED1 hears the same frame and shows it. It is a mirror, not ten LEDs: the second bar can never show anything the first does not.
How the LED tells a 0 from a 1, and why digitalWrite cannot.
Bits as pulse widths →Edit this page — content/books/ws2812-led-bar/where-the-chain-ends.mdx
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