ws2812: use PIO on RP2040/RP2350 transparently via build tags

Instead of adding a new Strip type, integrate PIO support directly into
the existing Device. NewWS2812() now uses PIO for hardware-timed control
on RP2040/RP2350 and falls back to bit-banging on other platforms.

No changes to the exported API surface.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: gandarez

examples/ws2812-strip/main.go

@@ -93,7 +93,6 @@ tinygo build -size short -o ./build/test.bin -target=m5stamp-c3          ./examp
 tinygo build -size short -o ./build/test.hex -target=feather-nrf52840 ./examples/is31fl3731/main.go
 tinygo build -size short -o ./build/test.hex -target=arduino   ./examples/ws2812
 tinygo build -size short -o ./build/test.hex -target=digispark ./examples/ws2812
-tinygo build -size short -o ./build/test.bin -target=pico2     ./examples/ws2812-strip
 tinygo build -size short -o ./build/test.hex -target=trinket-m0 ./examples/bme280/main.go
 tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/microphone/main.go
 tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/buzzer/main.go

smoketest.sh

@@ -1,9 +1,7 @@
 // Package ws2812 implements a driver for WS2812 and SK6812 RGB LED strips.
 //
-// For low-level control, use Device with NewWS2812 or NewSK6812.
-// For a higher-level API with pixel buffering and brightness control,
-// use Strip with NewStrip. On RP2040/RP2350, Strip uses PIO for
-// hardware-timed control; on other platforms it falls back to bit-banging.
+// On RP2040/RP2350, NewWS2812 uses PIO for hardware-timed control.
+// On other platforms it uses bit-banging.
 package ws2812 // import "tinygo.org/x/drivers/ws2812"
 
 //go:generate go run gen-ws2812.go -arch=cortexm 16 48 64 120 125 150 168 200
@@ -29,14 +27,11 @@ func New(pin machine.Pin) Device {
 	return NewWS2812(pin)
 }
 
-// New returns a new WS2812(RGB) driver.
-// It does not touch the pin object: you have
-// to configure it as an output pin before calling New.
+// NewWS2812 returns a new WS2812(RGB) driver.
+// On RP2040/RP2350, it uses PIO for hardware-timed control.
+// On other platforms, you must configure the pin as output before calling this.
 func NewWS2812(pin machine.Pin) Device {
-	return Device{
-		Pin:            pin,
-		writeColorFunc: writeColorsRGB,
-	}
+	return newWS2812Device(pin)
 }
 
 // New returns a new SK6812(RGBA) driver.

ws2812/strip.go

@@ -0,0 +1,10 @@
+//go:build !rp2040 && !rp2350
+
+package ws2812
+
+import "machine"
+
+// newWS2812Device creates a WS2812 device using the bit-bang driver.
+func newWS2812Device(pin machine.Pin) Device {
+	return Device{Pin: pin, writeColorFunc: writeColorsRGB}
+}

ws2812/strip_other.go

@@ -0,0 +1,33 @@
+//go:build rp2040 || rp2350
+
+package ws2812
+
+import (
+	"image/color"
+	"machine"
+
+	pio "github.com/tinygo-org/pio/rp2-pio"
+	"github.com/tinygo-org/pio/rp2-pio/piolib"
+)
+
+// newWS2812Device creates a WS2812 device using PIO for hardware-timed control.
+// If PIO initialization fails, it falls back to the bit-bang driver.
+func newWS2812Device(pin machine.Pin) Device {
+	sm, err := pio.PIO0.ClaimStateMachine()
+	if err != nil {
+		return Device{Pin: pin, writeColorFunc: writeColorsRGB}
+	}
+	ws, err := piolib.NewWS2812B(sm, pin)
+	if err != nil {
+		return Device{Pin: pin, writeColorFunc: writeColorsRGB}
+	}
+	return Device{
+		Pin: pin,
+		writeColorFunc: func(_ Device, buf []color.RGBA) error {
+			for _, c := range buf {
+				ws.PutRGB(c.R, c.G, c.B)
+			}
+			return nil
+		},
+	}
+}