machine/samd21: use PinMode for SPI SERCOM peripheral to allow for more configuration options on boards like Arduino Nano33-IoT that have many predefined pin mappings

Signed-off-by: Ron Evans <ron@hybridgroup.com>

src/machine/board_arduino_nano33.go

@@ -37,7 +37,7 @@ const (
 	A0 Pin = PA02 // ADC/AIN[0]
 	A1 Pin = PB02 // ADC/AIN[10]
 	A2 Pin = PA11 // ADC/AIN[19]
-	A3 Pin = PA10 // ADC/AIN[18]
+	A3 Pin = PA10 // ADC/AIN[18],
 	A4 Pin = PB08 // ADC/AIN[2], SCL:  SERCOM2/PAD[1]
 	A5 Pin = PB09 // ADC/AIN[3], SDA:  SERCOM2/PAD[1]
 	A6 Pin = PA09 // ADC/AIN[17]
@@ -118,19 +118,20 @@ var (
 
 // SPI pins
 const (
-	SPI0_SCK_PIN  Pin = PB11 // SCK: SERCOM4/PAD[3]
-	SPI0_MOSI_PIN Pin = PB10 // MOSI: SERCOM4/PAD[2]
-	SPI0_MISO_PIN Pin = PA12 // MISO: SERCOM4/PAD[0]
+	SPI0_SCK_PIN  Pin = A2 // SCK: SERCOM0/PAD[3]
+	SPI0_MOSI_PIN Pin = A3 // MOSI: SERCOM0/PAD[2]
+	SPI0_MISO_PIN Pin = A6 // MISO: SERCOM0/PAD[1]
 )
 
 // SPI on the Arduino Nano 33.
 var (
-	SPI0 = SPI{Bus: sam.SERCOM1_SPI,
+	SPI0 = SPI{Bus: sam.SERCOM0_SPI,
 		SCK:     SPI0_SCK_PIN,
 		MOSI:    SPI0_MOSI_PIN,
 		MISO:    SPI0_MISO_PIN,
 		DOpad:   spiTXPad2SCK3,
-		DIpad: sercomRXPad0}
+		DIpad:   sercomRXPad0,
+		PinMode: PinSERCOM}
 )
 
 // I2S pins

src/machine/board_circuitplay_express.go

@@ -119,7 +119,8 @@ var (
 		MOSI:    SPI0_MOSI_PIN,
 		MISO:    SPI0_MISO_PIN,
 		DOpad:   spiTXPad2SCK3,
-		DIpad: sercomRXPad0}
+		DIpad:   sercomRXPad0,
+		PinMode: PinSERCOMAlt}
 )
 
 // I2S pins

src/machine/board_feather-m0.go

@@ -93,7 +93,8 @@ var (
 		MOSI:    SPI0_MOSI_PIN,
 		MISO:    SPI0_MISO_PIN,
 		DOpad:   spiTXPad2SCK3,
-		DIpad: sercomRXPad0}
+		DIpad:   sercomRXPad0,
+		PinMode: PinSERCOMAlt}
 )
 
 // I2S pins

src/machine/board_itsybitsy-m0.go

@@ -95,7 +95,8 @@ var (
 		MOSI:    SPI0_MOSI_PIN,
 		MISO:    SPI0_MISO_PIN,
 		DOpad:   spiTXPad2SCK3,
-		DIpad: sercomRXPad0}
+		DIpad:   sercomRXPad0,
+		PinMode: PinSERCOMAlt}
 )
 
 // "Internal" SPI pins; SPI flash is attached to these on ItsyBitsy M0
@@ -113,7 +114,8 @@ var (
 		MOSI:    SPI1_MOSI_PIN,
 		MISO:    SPI1_MISO_PIN,
 		DOpad:   spiTXPad2SCK3,
-		DIpad: sercomRXPad1}
+		DIpad:   sercomRXPad1,
+		PinMode: PinSERCOMAlt}
 )
 
 // I2S pins

src/machine/board_trinket.go

@@ -70,7 +70,8 @@ var (
 		MOSI:    SPI0_MOSI_PIN,
 		MISO:    SPI0_MISO_PIN,
 		DOpad:   spiTXPad2SCK3,
-		DIpad: sercomRXPad0}
+		DIpad:   sercomRXPad0,
+		PinMode: PinSERCOMAlt}
 )
 
 // I2C pins

src/machine/machine_atsamd21.go

@@ -882,6 +882,7 @@ type SPI struct {
 	MISO    Pin
 	DOpad   int
 	DIpad   int
+	PinMode PinMode
 }
 
 // SPIConfig is used to store config info for SPI.
@@ -896,7 +897,6 @@ type SPIConfig struct {
 
 // Configure is intended to setup the SPI interface.
 func (spi SPI) Configure(config SPIConfig) {
-
 	config.SCK = spi.SCK
 	config.MOSI = spi.MOSI
 	config.MISO = spi.MISO
@@ -904,6 +904,8 @@ func (spi SPI) Configure(config SPIConfig) {
 	doPad := spi.DOpad
 	diPad := spi.DIpad
 
+	pinMode := spi.PinMode
+
 	// set default frequency
 	if config.Frequency == 0 {
 		config.Frequency = 4000000
@@ -915,9 +917,9 @@ func (spi SPI) Configure(config SPIConfig) {
 	}
 
 	// enable pins
-	config.SCK.Configure(PinConfig{Mode: PinSERCOMAlt})
-	config.MOSI.Configure(PinConfig{Mode: PinSERCOMAlt})
-	config.MISO.Configure(PinConfig{Mode: PinSERCOMAlt})
+	config.SCK.Configure(PinConfig{Mode: pinMode})
+	config.MOSI.Configure(PinConfig{Mode: pinMode})
+	config.MISO.Configure(PinConfig{Mode: pinMode})
 
 	// reset SERCOM
 	spi.Bus.CTRLA.SetBits(sam.SERCOM_SPI_CTRLA_SWRST)