machine/stm32: implement DeviceID() with unique ID per processor

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

src/machine/machine_stm32.go

@@ -2,7 +2,12 @@
 
 package machine
 
-import "device/stm32"
+import (
+	"device/stm32"
+
+	"runtime/volatile"
+	"unsafe"
+)
 
 const deviceName = stm32.Device
 
@@ -80,3 +85,20 @@ func (p Pin) PortMaskClear() (*uint32, uint32) {
 	pin := uint8(p) % 16
 	return &port.BSRR.Reg, 1 << (pin + 16)
 }
+
+var deviceID [12]byte
+
+// DeviceID returns an identifier that is unique within
+// a particular chipset.
+//
+// The identity is one burnt into the MCU itself.
+//
+// The length of the device ID for STM32 is 12 bytes (96 bits).
+func DeviceID() []byte {
+	for i := 0; i < len(deviceID); i++ {
+		word := (*volatile.Register32)(unsafe.Pointer(deviceIDAddr[i/4])).Get()
+		deviceID[i] = byte(word >> ((i % 4) * 8))
+	}
+
+	return deviceID[:]
+}

src/machine/machine_stm32f103.go

@@ -15,6 +15,8 @@ func CPUFrequency() uint32 {
 	return 72000000
 }
 
+var deviceIDAddr = []uintptr{0x1FFFF7E8, 0x1FFFF7EC, 0x1FFFF7F0}
+
 // Internal use: configured speed of the APB1 and APB2 timers, this should be kept
 // in sync with any changes to runtime package which configures the oscillators
 // and clock frequencies

src/machine/machine_stm32f4.go

@@ -14,6 +14,8 @@ import (
 	"unsafe"
 )
 
+var deviceIDAddr = []uintptr{0x1FFF7A10, 0x1FFF7A14, 0x1FFF7A18}
+
 const (
 	PA0  = portA + 0
 	PA1  = portA + 1

src/machine/machine_stm32f7.go

@@ -11,6 +11,8 @@ import (
 	"unsafe"
 )
 
+var deviceIDAddr = []uintptr{0x1FF0F420, 0x1FF0F424, 0x1FF0F428}
+
 // Alternative peripheral pin functions
 const (
 	AF0_SYSTEM                               = 0

src/machine/machine_stm32l0.go

@@ -13,6 +13,8 @@ func CPUFrequency() uint32 {
 	return 32000000
 }
 
+var deviceIDAddr = []uintptr{0x1FF80050, 0x1FF80054, 0x1FF80058}
+
 // Internal use: configured speed of the APB1 and APB2 timers, this should be kept
 // in sync with any changes to runtime package which configures the oscillators
 // and clock frequencies

src/machine/machine_stm32l4.go

@@ -13,6 +13,8 @@ import (
 
 // Peripheral abstraction layer for the stm32l4
 
+var deviceIDAddr = []uintptr{0x1FFF7590, 0x1FFF7594, 0x1FFF7598}
+
 const (
 	AF0_SYSTEM             = 0
 	AF1_TIM1_2_LPTIM1      = 1

src/machine/machine_stm32l5.go

@@ -11,6 +11,8 @@ import (
 	"unsafe"
 )
 
+var deviceIDAddr = []uintptr{0x0BFA0590, 0x0BFA0594, 0x0BFA0598}
+
 const (
 	AF0_SYSTEM                                = 0
 	AF1_TIM1_2_5_8_LPTIM1                     = 1

src/machine/machine_stm32wlx.go

@@ -14,6 +14,8 @@ import (
 	"unsafe"
 )
 
+var deviceIDAddr = []uintptr{0x1FFF7590, 0x1FFF7594, 0x1FFF7598}
+
 const (
 	AF0_SYSTEM             = 0
 	AF1_TIM1_2_LPTIM1      = 1