targets: simulate Circuit Playground Express in play.tinygo.org

This requires a number of changes to atsamd21 code. It's not a very
clean separation, but I couldn't come up with a better one.

Makefile

@@ -188,6 +188,8 @@ smoketest:
 	@$(MD5SUM) test.wasm
 	$(TINYGO) build             -o test.wasm -tags=pca10056             examples/blinky2
 	@$(MD5SUM) test.wasm
+	$(TINYGO) build             -o test.wasm -tags=circuitplay_express  examples/blinky1
+	@$(MD5SUM) test.wasm
 	# test all targets/boards
 	$(TINYGO) build -size short -o test.hex -target=pca10040-s132v6     examples/blinky1
 	@$(MD5SUM) test.hex

src/machine/board_atsamd21.go

@@ -0,0 +1,73 @@
+// +build sam,atsamd21 circuitplay_express
+
+package machine
+
+const CPU_FREQUENCY = 48000000
+
+// Hardware pins
+const (
+	PA00 Pin = 0
+	PA01 Pin = 1
+	PA02 Pin = 2
+	PA03 Pin = 3
+	PA04 Pin = 4
+	PA05 Pin = 5
+	PA06 Pin = 6
+	PA07 Pin = 7
+	PA08 Pin = 8
+	PA09 Pin = 9
+	PA10 Pin = 10
+	PA11 Pin = 11
+	PA12 Pin = 12
+	PA13 Pin = 13
+	PA14 Pin = 14
+	PA15 Pin = 15
+	PA16 Pin = 16
+	PA17 Pin = 17
+	PA18 Pin = 18
+	PA19 Pin = 19
+	PA20 Pin = 20
+	PA21 Pin = 21
+	PA22 Pin = 22
+	PA23 Pin = 23
+	PA24 Pin = 24
+	PA25 Pin = 25
+	PA26 Pin = 26
+	PA27 Pin = 27
+	PA28 Pin = 28
+	PA29 Pin = 29
+	PA30 Pin = 30
+	PA31 Pin = 31
+	PB00 Pin = 32
+	PB01 Pin = 33
+	PB02 Pin = 34
+	PB03 Pin = 35
+	PB04 Pin = 36
+	PB05 Pin = 37
+	PB06 Pin = 38
+	PB07 Pin = 39
+	PB08 Pin = 40
+	PB09 Pin = 41
+	PB10 Pin = 42
+	PB11 Pin = 43
+	PB12 Pin = 44
+	PB13 Pin = 45
+	PB14 Pin = 46
+	PB15 Pin = 47
+	PB16 Pin = 48
+	PB17 Pin = 49
+	PB18 Pin = 50
+	PB19 Pin = 51
+	PB20 Pin = 52
+	PB21 Pin = 53
+	PB22 Pin = 54
+	PB23 Pin = 55
+	PB24 Pin = 56
+	PB25 Pin = 57
+	PB26 Pin = 58
+	PB27 Pin = 59
+	PB28 Pin = 60
+	PB29 Pin = 61
+	PB30 Pin = 62
+	PB31 Pin = 63
+)

src/machine/board_circuitplay_express.go

@@ -1,9 +1,7 @@
-// +build sam,atsamd21,circuitplay_express
+// +build circuitplay_express
 
 package machine
 
-import "device/sam"
-
 // used to reset into bootloader
 const RESET_MAGIC_VALUE = 0xf01669ef
 
@@ -68,20 +66,6 @@ const (
 	UART_RX_PIN = PB09 // PORTB
 )
 
-// UART1 on the Circuit Playground Express.
-var (
-	UART1 = UART{
-		Buffer: NewRingBuffer(),
-		Bus:    sam.SERCOM4_USART,
-		SERCOM: 4,
-	}
-)
-
-//go:export SERCOM1_IRQHandler
-func handleUART1() {
-	defaultUART1Handler()
-}
-
 // I2C pins
 const (
 	SDA_PIN = PB02 // I2C0 external
@@ -91,20 +75,6 @@ const (
 	SCL1_PIN = PA01 // I2C1 internal
 )
 
-// I2C on the Circuit Playground Express.
-var (
-	// external device
-	I2C0 = I2C{
-		Bus:    sam.SERCOM5_I2CM,
-		SERCOM: 5,
-	}
-	// internal device
-	I2C1 = I2C{
-		Bus:    sam.SERCOM1_I2CM,
-		SERCOM: 1,
-	}
-)
-
 // SPI pins (internal flash)
 const (
 	SPI0_SCK_PIN  = PA21 // SCK: SERCOM3/PAD[3]
@@ -112,22 +82,9 @@ const (
 	SPI0_MISO_PIN = PA16 // MISO: SERCOM3/PAD[0]
 )
 
-// SPI on the Circuit Playground Express.
-var (
-	SPI0 = SPI{
-		Bus:    sam.SERCOM3_SPI,
-		SERCOM: 3,
-	}
-)
-
 // I2S pins
 const (
 	I2S_SCK_PIN = PA10
 	I2S_SD_PIN  = PA08
 	I2S_WS_PIN  = NoPin // no WS, instead uses SCK to sync
 )
-
-// I2S on the Circuit Playground Express.
-var (
-	I2S0 = I2S{Bus: sam.I2S}
-)

src/machine/board_circuitplay_express_baremetal.go

@@ -0,0 +1,46 @@
+// +build sam,atsamd21,circuitplay_express
+
+package machine
+
+import "device/sam"
+
+// UART1 on the Circuit Playground Express.
+var (
+	UART1 = UART{
+		Buffer: NewRingBuffer(),
+		Bus:    sam.SERCOM4_USART,
+		SERCOM: 4,
+	}
+)
+
+//go:export SERCOM1_IRQHandler
+func handleUART1() {
+	defaultUART1Handler()
+}
+
+// I2C on the Circuit Playground Express.
+var (
+	// external device
+	I2C0 = I2C{
+		Bus:    sam.SERCOM5_I2CM,
+		SERCOM: 5,
+	}
+	// internal device
+	I2C1 = I2C{
+		Bus:    sam.SERCOM1_I2CM,
+		SERCOM: 1,
+	}
+)
+
+// SPI on the Circuit Playground Express.
+var (
+	SPI0 = SPI{
+		Bus:    sam.SERCOM3_SPI,
+		SERCOM: 3,
+	}
+)
+
+// I2S on the Circuit Playground Express.
+var (
+	I2S0 = I2S{Bus: sam.I2S}
+)

src/machine/machine_atsamd21.go

@@ -14,8 +14,6 @@ import (
 	"unsafe"
 )
 
-const CPU_FREQUENCY = 48000000
-
 type PinMode uint8
 
 const (
@@ -35,74 +33,6 @@ const (
 	PinInputPulldown PinMode = 12
 )
 
-// Hardware pins
-const (
-	PA00 Pin = 0
-	PA01 Pin = 1
-	PA02 Pin = 2
-	PA03 Pin = 3
-	PA04 Pin = 4
-	PA05 Pin = 5
-	PA06 Pin = 6
-	PA07 Pin = 7
-	PA08 Pin = 8
-	PA09 Pin = 9
-	PA10 Pin = 10
-	PA11 Pin = 11
-	PA12 Pin = 12
-	PA13 Pin = 13
-	PA14 Pin = 14
-	PA15 Pin = 15
-	PA16 Pin = 16
-	PA17 Pin = 17
-	PA18 Pin = 18
-	PA19 Pin = 19
-	PA20 Pin = 20
-	PA21 Pin = 21
-	PA22 Pin = 22
-	PA23 Pin = 23
-	PA24 Pin = 24
-	PA25 Pin = 25
-	PA26 Pin = 26
-	PA27 Pin = 27
-	PA28 Pin = 28
-	PA29 Pin = 29
-	PA30 Pin = 30
-	PA31 Pin = 31
-	PB00 Pin = 32
-	PB01 Pin = 33
-	PB02 Pin = 34
-	PB03 Pin = 35
-	PB04 Pin = 36
-	PB05 Pin = 37
-	PB06 Pin = 38
-	PB07 Pin = 39
-	PB08 Pin = 40
-	PB09 Pin = 41
-	PB10 Pin = 42
-	PB11 Pin = 43
-	PB12 Pin = 44
-	PB13 Pin = 45
-	PB14 Pin = 46
-	PB15 Pin = 47
-	PB16 Pin = 48
-	PB17 Pin = 49
-	PB18 Pin = 50
-	PB19 Pin = 51
-	PB20 Pin = 52
-	PB21 Pin = 53
-	PB22 Pin = 54
-	PB23 Pin = 55
-	PB24 Pin = 56
-	PB25 Pin = 57
-	PB26 Pin = 58
-	PB27 Pin = 59
-	PB28 Pin = 60
-	PB29 Pin = 61
-	PB30 Pin = 62
-	PB31 Pin = 63
-)
-
 const (
 	pinPadMapSERCOM0Pad0 byte = (0x10 << 1) | 0x00
 	pinPadMapSERCOM1Pad0 byte = (0x20 << 1) | 0x00