feat(machine/stm32): add STM32F401 and NUCLEO-F401RE support

make/smoketest.mk

@@ -362,6 +362,8 @@ ifneq ($(STM32), 0)
 	@$(MD5SUM) $(SMOKE_OUT).hex
 	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=nucleo-f103rb       examples/blinky1
 	@$(MD5SUM) $(SMOKE_OUT).hex
+	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=nucleo-f401re       examples/blinky1
+	@$(MD5SUM) $(SMOKE_OUT).hex
 	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=nucleo-f722ze       examples/blinky1
 	@$(MD5SUM) $(SMOKE_OUT).hex
 	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=nucleo-h753zi       examples/blinky1
@@ -384,6 +386,8 @@ ifneq ($(STM32), 0)
 	@$(MD5SUM) $(SMOKE_OUT).hex
 	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=stm32f4disco-1      examples/pwm
 	@$(MD5SUM) $(SMOKE_OUT).hex
+	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=nucleo-f401re       examples/pwm
+	@$(MD5SUM) $(SMOKE_OUT).hex
 	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=stm32f469disco      examples/blinky1
 	@$(MD5SUM) $(SMOKE_OUT).hex
 	$(TINYGO) build -size short -o $(SMOKE_OUT).hex -target=lorae5              examples/blinky1

src/crypto/rand/rand_baremetal.go

@@ -1,4 +1,4 @@
-//go:build nrf || (stm32 && !(stm32f103 || stm32l0x1 || stm32u0)) || (sam && atsamd51) || (sam && atsame5x) || esp32c3 || esp32s3 || tkey || (tinygo.riscv32 && virt)
+//go:build nrf || (stm32 && !(stm32f103 || stm32l0x1 || stm32u0 || stm32f401)) || (sam && atsamd51) || (sam && atsame5x) || esp32c3 || esp32s3 || tkey || (tinygo.riscv32 && virt)
 
 // If you update the above build constraint, you'll probably also need to update
 // src/runtime/rand_hwrng.go.

src/examples/pwm/nucleo-f401re.go

@@ -0,0 +1,13 @@
+//go:build nucleof401re
+
+package main
+
+import "machine"
+
+// TIM3 is reserved by the runtime tick timer on STM32F401.
+// Use TIM2 instead: PB10=D6 (TIM2_CH3/AF1), PB3=D3 (TIM2_CH2/AF1).
+var (
+	pwm  = &machine.TIM2
+	pinA = machine.D6
+	pinB = machine.D3
+)

src/machine/board_nucleof401re.go

@@ -0,0 +1,140 @@
+//go:build nucleof401re
+
+// Schematic: https://www.st.com/resource/en/user_manual/um1724-stm32-nucleo64-boards-mb1136-stmicroelectronics.pdf
+// Datasheet: https://www.st.com/resource/en/datasheet/stm32f401re.pdf
+
+package machine
+
+import (
+	"device/stm32"
+	"runtime/interrupt"
+)
+
+const xtalHz = 8_000_000
+
+const (
+	// Arduino Pins
+	A0 = PA0
+	A1 = PA1
+	A2 = PA4
+	A3 = PB0
+	A4 = PC1
+	A5 = PC0
+
+	D0  = PA3
+	D1  = PA2
+	D2  = PA10
+	D3  = PB3
+	D4  = PB5
+	D5  = PB4
+	D6  = PB10
+	D7  = PA8
+	D8  = PA9
+	D9  = PC7
+	D10 = PB6
+	D11 = PA7
+	D12 = PA6
+	D13 = PA5
+	D14 = PB9
+	D15 = PB8
+)
+
+// Analog pins (ADC1 channels).
+// examples/adc uses ADC2 (PA2). That pin is ST-Link VCP TX, so use A0 instead.
+const (
+	ADC0  = PA0
+	ADC1  = PA1
+	ADC2  = PA2
+	ADC3  = PA3
+	ADC4  = PA4
+	ADC5  = PA5
+	ADC6  = PA6
+	ADC7  = PA7
+	ADC8  = PB0
+	ADC9  = PB1
+	ADC10 = PC0
+	ADC11 = PC1
+	ADC12 = PC2
+	ADC13 = PC3
+	ADC14 = PC4
+	ADC15 = PC5
+)
+
+// User LD2: the green LED is a user LED connected to Arduino signal D13
+// corresponding to STM32 I/O PA5.
+const (
+	LED         = LED_BUILTIN
+	LED_BUILTIN = LED_GREEN
+	LED_GREEN   = PA5
+)
+
+// BUTTON is the user button B1 connected to PC13 (active low).
+const BUTTON = PC13
+
+const (
+	// UART pins
+	// PA2 and PA3 are connected to the ST-Link Virtual Com Port (VCP).
+	UART_TX_PIN  = PA2
+	UART_RX_PIN  = PA3
+	UART1_TX_PIN = UART_TX_PIN
+	UART1_RX_PIN = UART_RX_PIN
+
+	// USART1 on Arduino D8 (PA9 = TX) / D2 (PA10 = RX).
+	// Use for external UART communication (e.g. with another board).
+	UART2_TX_PIN = PA9
+	UART2_RX_PIN = PA10
+
+	// I2C pins
+	// PB8 / Arduino D15 is SCL, PB9 / Arduino D14 is SDA.
+	I2C0_SCL_PIN = PB8
+	I2C0_SDA_PIN = PB9
+
+	// SPI pins
+	SPI1_SCK_PIN = PA5
+	SPI1_SDI_PIN = PA6
+	SPI1_SDO_PIN = PA7
+	SPI0_SCK_PIN = SPI1_SCK_PIN
+	SPI0_SDI_PIN = SPI1_SDI_PIN
+	SPI0_SDO_PIN = SPI1_SDO_PIN
+)
+
+var (
+	// USART2 is the hardware serial port connected to the onboard ST-LINK
+	// debugger, exposed as a virtual COM port over USB.
+	UART1  = &_UART1
+	_UART1 = UART{
+		Buffer:            NewRingBuffer(),
+		Bus:               stm32.USART2,
+		TxAltFuncSelector: AF7_USART1_2_3,
+		RxAltFuncSelector: AF7_USART1_2_3,
+	}
+	DefaultUART = UART1
+
+	// USART1 on PA9 (TX=D8) / PA10 (RX=D2). Use for external communication.
+	UART2  = &_UART2
+	_UART2 = UART{
+		Buffer:            NewRingBuffer(),
+		Bus:               stm32.USART1,
+		TxAltFuncSelector: AF7_USART1_2_3,
+		RxAltFuncSelector: AF7_USART1_2_3,
+	}
+
+	// I2C1 is documented; I2C0 is an alias.
+	I2C1 = &I2C{
+		Bus:             stm32.I2C1,
+		AltFuncSelector: AF4_I2C1_2_3,
+	}
+	I2C0 = I2C1
+
+	// SPI1 is documented; SPI0 is an alias.
+	SPI1 = &SPI{
+		Bus:             stm32.SPI1,
+		AltFuncSelector: AF5_SPI1_SPI2,
+	}
+	SPI0 = SPI1
+)
+
+func init() {
+	UART1.Interrupt = interrupt.New(stm32.IRQ_USART2, _UART1.handleInterrupt)
+	UART2.Interrupt = interrupt.New(stm32.IRQ_USART1, _UART2.handleInterrupt)
+}

src/machine/machine_stm32_adc_f4.go

@@ -37,12 +37,15 @@ func InitADC() {
 func (a ADC) Configure(ADCConfig) {
 	a.Pin.ConfigureAltFunc(PinConfig{Mode: PinInputAnalog}, 0)
 
-	// set sample time
+	// set sample time (84 ADC cycles). Each SMPx field is 3 bits wide; the
+	// encoding for 84 cycles is 4. Named Cycles84 constants are not present
+	// in every F4 SVD, so use the literal values.
+	const cycles84 = 4
 	ch := a.getChannel()
 	if ch > 9 {
-		stm32.ADC1.SMPR1.SetBits(stm32.ADC_SMPR1_SMP11_Cycles84 << (ch - 10) * stm32.ADC_SMPR1_SMP11_Pos)
+		stm32.ADC1.SMPR1.SetBits(cycles84 << ((ch - 10) * 3))
 	} else {
-		stm32.ADC1.SMPR2.SetBits(stm32.ADC_SMPR2_SMP1_Cycles84 << (ch * stm32.ADC_SMPR2_SMP1_Pos))
+		stm32.ADC1.SMPR2.SetBits(cycles84 << (ch * 3))
 	}
 
 	return

src/machine/machine_stm32_otgfs_usb.go

@@ -1,4 +1,6 @@
-//go:build stm32f4 || stm32f7
+// NUCLEO-F401RE has no USB OTG connector. This chip-wide exclude
+// also blocks later F401 boards that have USB (for example Blackpill F401CC).
+//go:build (stm32f4 && !stm32f401) || stm32f7
 
 package machine
 

src/machine/machine_stm32_rng.go

@@ -1,4 +1,4 @@
-//go:build stm32 && !(stm32f103 || stm32l0x1 || stm32g0 || stm32u0)
+//go:build stm32 && !(stm32f103 || stm32l0x1 || stm32g0 || stm32u0 || stm32f401)
 
 package machine