diff --git a/README.md b/README.md
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--- a/README.md
+++ b/README.md
@@ -12,4 +12,5 @@ This repository specifies the control protocol implemented by [gex-core](https:/
 
 - [UNIT_DO.md](UNIT_DO.md) - Digital Output
 - [UNIT_DI.md](UNIT_DI.md) - Digital Input
+- [UNIT_NEOPIXEL.md](UNIT_NEOPIXEL.md) - NeoPixel driver
 
diff --git a/UNIT_NEOPIXEL.md b/UNIT_NEOPIXEL.md
new file mode 100644
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+++ b/UNIT_NEOPIXEL.md
@@ -0,0 +1,44 @@
+# NeoPixel
+
+Implements the NeoPixel protocol for driving addressable LED strips.
+The strip length is configured in the unit settings.
+
+## Commands
+
+### CLEAR (0x00)
+Set all pixels to black. This is automatically executed on start-up to clear the strip.
+
+### LOAD (0x01)
+Load packed RGB data to the strip.
+
+*Payload:*
+
+- a byte array `(R,G,B)` x length
+
+### LOAD_U32_LE (0x02)
+Load 32-bit `0x00BBGGRR` words encoded in little-endian as `(R,G,B,0)`.
+This is more convenient for the PC script, but wastes 1/4 of the payload by padding
+null bytes.
+
+*Payload:*
+
+- a byte array `(R,G,B,0)` x length
+
+### LOAD_U32_BE (0x03)
+Load 32-bit `0x00BBGGRR` words encoded in big-endian as `(0,B,G,R)`.
+
+*Payload:*
+
+- a byte array `(0,B,G,R)` x length
+
+
+### GET_LEN (0x04)
+Read the neopixel strip length as configured in the settings.
+
+*Response:*
+
+- u16 - number of pixels
+
+## Events
+
+*No events defined for this unit type.*