machine/atsamd21: uses different required magic values for BOSSA and UF2 bootloaders

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

src/machine/board_arduino_nano33.go

@@ -8,6 +8,9 @@ package machine
 
 import "device/sam"
 
+// used to reset into bootloader
+const RESET_MAGIC_VALUE = 0x07738135
+
 // GPIO Pins
 const (
 	RX0 Pin = PB23 // UART2 RX

src/machine/board_circuitplay_express.go

@@ -4,6 +4,9 @@ package machine
 
 import "device/sam"
 
+// used to reset into bootloader
+const RESET_MAGIC_VALUE = 0xf01669ef
+
 // GPIO Pins
 const (
 	D0  = PB09

src/machine/board_feather-m0.go

@@ -4,6 +4,9 @@ package machine
 
 import "device/sam"
 
+// used to reset into bootloader
+const RESET_MAGIC_VALUE = 0xf01669ef
+
 // GPIO Pins
 const (
 	D0  = PA11  // UART0 RX

src/machine/board_itsybitsy-m0.go

@@ -6,6 +6,9 @@ import (
 	"device/sam"
 )
 
+// used to reset into bootloader
+const RESET_MAGIC_VALUE = 0xf01669ef
+
 // GPIO Pins
 const (
 	D0  = PA11 // UART0 RX

src/machine/board_trinket.go

@@ -4,6 +4,9 @@ package machine
 
 import "device/sam"
 
+// used to reset into bootloader
+const RESET_MAGIC_VALUE = 0xf01669ef
+
 // GPIO Pins
 const (
 	D0  = PA08 // PWM available

src/machine/machine_atsamd21.go

@@ -2081,7 +2081,7 @@ func ResetProcessor() {
 
 	// Perform magic reset into bootloader, as mentioned in
 	// https://github.com/arduino/ArduinoCore-samd/issues/197
-	*(*uint32)(unsafe.Pointer(uintptr(0x20007FFC))) = 0x07738135
+	*(*uint32)(unsafe.Pointer(uintptr(0x20007FFC))) = RESET_MAGIC_VALUE
 
 	arm.SystemReset()
 }