ws2812: make AVR support more robust

* Merge AVR support for Digispark and non-Digispark
* Fix the error "inline assembly requires more registers than available"
* Use a single file for all AVR targets, in a similar style as the
  Xtensa support.

Makefile

@@ -132,6 +132,8 @@ smoke-test:
 	tinygo build -size short -o ./build/test.hex -target=circuitplay-express ./examples/ws2812
 	@md5sum ./build/test.hex
 ifneq ($(AVR), 0)
+	tinygo build -size short -o ./build/test.hex -target=arduino   ./examples/ws2812
+	@md5sum ./build/test.hex
 	tinygo build -size short -o ./build/test.hex -target=digispark ./examples/ws2812
 	@md5sum ./build/test.hex
 endif

examples/ws2812/arduino.go

@@ -0,0 +1,9 @@
+// +build arduino
+
+package main
+
+import "machine"
+
+// Replace neo in the code below to match the pin
+// that you are using if different.
+var neo = machine.D2

examples/ws2812/others.go

@@ -1,4 +1,4 @@
-// +build !digispark
+// +build !digispark,!arduino
 
 package main
 

ws2812/ws2812.go

@@ -2,10 +2,13 @@
 package ws2812 // import "tinygo.org/x/drivers/ws2812"
 
 import (
+	"errors"
 	"image/color"
 	"machine"
 )
 
+var errUnknownClockSpeed = errors.New("ws2812: unknown CPU clock speed")
+
 // Device wraps a pin object for an easy driver interface.
 type Device struct {
 	Pin machine.Pin

ws2812/ws2812_avr.go

@@ -0,0 +1,58 @@
+// +build avr
+
+package ws2812
+
+// This file implements the WS2812 protocol for AVR microcontrollers.
+
+import (
+	"device/avr"
+	"machine"
+)
+
+// Send a single byte using the WS2812 protocol.
+func (d Device) WriteByte(c byte) error {
+	// On AVR, the port is always the same for setting and clearing a register
+	// so use only one. This avoids the following error:
+	//     error: inline assembly requires more registers than available
+	// Probably this is about pointer registers, which are very limited on AVR.
+	port, maskSet := d.Pin.PortMaskSet()
+	_, maskClear := d.Pin.PortMaskClear()
+
+	switch machine.CPUFrequency() {
+	case 16e6: // 16MHz
+		// See:
+		// https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
+		// T0H: 4  cycles or 250ns
+		// T0L: 14 cycles or 875ns -> together 18 cycles or 1125ns
+		// T1H: 9  cycles or 562ns
+		// T1L: 8  cycles or 500ns -> together 17 cycles or 1062ns
+		avr.AsmFull(`
+	send_bit:
+		st    {portSet}, {maskSet}     ; [2]   set output high
+		lsl   {value}                  ; [1]   shift off the next bit, store it in C
+		brcs  skip_store               ; [1/2] branch if this bit is high (long pulse)
+		st    {portClear}, {maskClear} ; [2]   set output low (short pulse)
+	skip_store:
+		nop                            ; [4]   wait before changing the output again
+		nop
+		nop
+		nop
+		st    {portClear}, {maskClear} ; [2]   set output low (end of pulse)
+		nop                            ; [3]
+		nop
+		nop
+		subi  {i}, 1                   ; [1]   subtract one (for the loop)
+		brne  send_bit                 ; [1/2] send the next bit, if not at the end of the loop
+	`, map[string]interface{}{
+			"value":     c,
+			"i":         byte(8),
+			"maskSet":   maskSet,
+			"portSet":   port,
+			"maskClear": maskClear,
+			"portClear": port,
+		})
+		return nil
+	default:
+		return errUnknownClockSpeed
+	}
+}

ws2812/ws2812_avr_16m.go

@@ -1,49 +0,0 @@
-// +build atmega328p
-
-package ws2812
-
-// This file implements the WS2812 protocol for 16MHz AVR microcontrollers.
-
-import (
-	"device/avr"
-)
-
-// Send a single byte using the WS2812 protocol.
-func (d Device) WriteByte(c byte) error {
-	// For the AVR at 16MHz
-	portSet, maskSet := d.Pin.PortMaskSet()
-	portClear, maskClear := d.Pin.PortMaskClear()
-
-	// See:
-	// https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
-	// T0H: 4  cycles or 250ns
-	// T0L: 14 cycles or 875ns -> together 18 cycles or 1125ns
-	// T1H: 9  cycles or 562ns
-	// T1L: 8  cycles or 500ns -> together 17 cycles or 1062ns
-	avr.AsmFull(`
-	send_bit:
-		st    {portSet}, {maskSet}     ; [2]   set output high
-		lsl   {value}                  ; [1]   shift off the next bit, store it in C
-		brcs  skip_store               ; [1/2] branch if this bit is high (long pulse)
-		st    {portClear}, {maskClear} ; [2]   set output low (short pulse)
-	skip_store:
-		nop                            ; [4]   wait before changing the output again
-		nop
-		nop
-		nop
-		st    {portClear}, {maskClear} ; [2]   set output low (end of pulse)
-		nop                            ; [3]
-		nop
-		nop
-		subi  {i}, 1                   ; [1]   subtract one (for the loop)
-		brne  send_bit                 ; [1/2] send the next bit, if not at the end of the loop
-	`, map[string]interface{}{
-		"value":     c,
-		"i":         8,
-		"maskSet":   maskSet,
-		"portSet":   portSet,
-		"maskClear": maskClear,
-		"portClear": portClear,
-	})
-	return nil
-}

ws2812/ws2812_avr_digispark.go

@@ -1,50 +0,0 @@
-// +build digispark
-
-package ws2812
-
-// This file implements the WS2812 protocol for 16.5MHz Digispark AVR microcontrollers.
-// This is a slightly different implementation than the one for the atmega to work around a compiler bug.
-
-import (
-	"device/avr"
-)
-
-// Send a single byte using the WS2812 protocol.
-func (d Device) WriteByte(c byte) error {
-	// For the AVR at 16MHz
-	portSet, maskSet := d.Pin.PortMaskSet()
-	portClear, maskClear := d.Pin.PortMaskClear()
-
-	// See:
-	// https://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/
-	// T0H: 4  cycles or 250ns
-	// T0L: 14 cycles or 875ns -> together 18 cycles or 1125ns
-	// T1H: 9  cycles or 562ns
-	// T1L: 8  cycles or 500ns -> together 17 cycles or 1062ns
-	avr.AsmFull(`
-	send_bit:
-		st    {portSet}, {maskSet}     ; [2]   set output high
-		lsl   {value}                  ; [1]   shift off the next bit, store it in C
-		brcs  skip_store               ; [1/2] branch if this bit is high (long pulse)
-		st    {portClear}, {maskClear} ; [2]   set output low (short pulse)
-	skip_store:
-		nop                            ; [4]   wait before changing the output again
-		nop
-		nop
-		nop
-		st    {portClear}, {maskClear} ; [2]   set output low (end of pulse)
-		nop                            ; [3]
-		nop
-		nop
-		subi  {i}, 1                   ; [1]   subtract one (for the loop)
-		brne  send_bit                 ; [1/2] send the next bit, if not at the end of the loop
-	`, map[string]interface{}{
-		"value":     c,
-		"i":         byte(8),
-		"maskSet":   maskSet,
-		"portSet":   portSet,
-		"maskClear": maskClear,
-		"portClear": portClear,
-	})
-	return nil
-}

ws2812/ws2812_xtensa.go

@@ -4,13 +4,10 @@ package ws2812
 
 import (
 	"device"
-	"errors"
 	"machine"
 	"unsafe"
 )
 
-var errUnknownClockSpeed = errors.New("ws2812: unknown CPU clock speed")
-
 func (d Device) WriteByte(c byte) error {
 	portSet, maskSet := d.Pin.PortMaskSet()
 	portClear, maskClear := d.Pin.PortMaskClear()