machine/stm32: add support for stm32f103xx UART

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

src/device/stm32/stm32f103xx-bitfields.go

@@ -0,0 +1,44 @@
+// Hand created file. DO NOT DELETE.
+// STM32F103XX bitfield definitions that are not auto-generated by gen-device-svd.py
+
+// +build stm32,stm32f103xx
+
+package stm32
+
+const (
+	// Flash Access Control Register flag values.
+	FLASH_ACR_LATENCY_0 = 0x00000001
+	FLASH_ACR_LATENCY_1 = 0x00000002
+	FLASH_ACR_LATENCY_2 = 0x00000004
+
+	// Reset and Clock Control Control Register flag values.
+	RCC_CFGR_SW_HSI = 0
+	RCC_CFGR_SW_HSE = 1
+	RCC_CFGR_SW_PLL = 2
+
+	RCC_CFGR_SWS_HSI = 0x00000000
+	RCC_CFGR_SWS_HSE = 0x00000004
+	RCC_CFGR_SWS_PLL = 0x00000008
+
+	RCC_CFGR_PPRE1_DIV_NONE = 0x00000000
+	RCC_CFGR_PPRE1_DIV_2    = 0x00000400
+	RCC_CFGR_PPRE1_DIV_4    = 0x00000500
+	RCC_CFGR_PPRE1_DIV_8    = 0x00000600
+	RCC_CFGR_PPRE1_DIV_16   = 0x00000700
+
+	RCC_CFGR_PLLMUL_2  = 0x00000000
+	RCC_CFGR_PLLMUL_3  = 0x00040000
+	RCC_CFGR_PLLMUL_4  = 0x00080000
+	RCC_CFGR_PLLMUL_5  = 0x000C0000
+	RCC_CFGR_PLLMUL_6  = 0x00100000
+	RCC_CFGR_PLLMUL_7  = 0x00140000
+	RCC_CFGR_PLLMUL_8  = 0x00180000
+	RCC_CFGR_PLLMUL_9  = 0x001C0000
+	RCC_CFGR_PLLMUL_10 = 0x00200000
+	RCC_CFGR_PLLMUL_11 = 0x00240000
+	RCC_CFGR_PLLMUL_12 = 0x00280000
+	RCC_CFGR_PLLMUL_13 = 0x002C0000
+	RCC_CFGR_PLLMUL_14 = 0x00300000
+	RCC_CFGR_PLLMUL_15 = 0x00340000
+	RCC_CFGR_PLLMUL_16 = 0x00380000
+)

src/machine/machine_stm32.go

@@ -4,17 +4,8 @@ package machine
 
 // Peripheral abstraction layer for the stm32.
 
-import (
-	"device/stm32"
-)
-
 type GPIOMode uint8
 
-const (
-	GPIO_INPUT  = 0 // Input mode
-	GPIO_OUTPUT = 2 // Output mode, max speed 2MHz
-)
-
 const (
 	portA = iota * 16
 	portB
@@ -24,54 +15,3 @@ const (
 	portF
 	portG
 )
-
-func (p GPIO) getPort() *stm32.GPIO_Type {
-	switch p.Pin / 16 {
-	case 0:
-		return stm32.GPIOA
-	case 1:
-		return stm32.GPIOB
-	case 2:
-		return stm32.GPIOC
-	case 3:
-		return stm32.GPIOD
-	case 4:
-		return stm32.GPIOE
-	case 5:
-		return stm32.GPIOF
-	case 6:
-		return stm32.GPIOG
-	default:
-		panic("machine: unknown port")
-	}
-}
-
-// Configure this pin with the given configuration.
-func (p GPIO) Configure(config GPIOConfig) {
-	// Enable clock.
-	// Do this always, as it isn't known whether the clock has already been
-	// enabled.
-	stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPCEN
-
-	// Configure the GPIO pin.
-	port := p.getPort()
-	pin := p.Pin % 16
-	pos := p.Pin % 8 * 4
-	if pin < 8 {
-		port.CRL = stm32.RegValue((uint32(port.CRL) &^ (0xf << pos)) | (uint32(config.Mode) << pos))
-	} else {
-		port.CRH = stm32.RegValue((uint32(port.CRH) &^ (0xf << pos)) | (uint32(config.Mode) << pos))
-	}
-}
-
-// Set the pin to high or low.
-// Warning: only use this on an output pin!
-func (p GPIO) Set(high bool) {
-	port := p.getPort()
-	pin := p.Pin % 16
-	if high {
-		port.BSRR = 1 << pin
-	} else {
-		port.BSRR = 1 << (pin + 16)
-	}
-}

src/machine/machine_stm32f103xx.go

@@ -0,0 +1,161 @@
+// +build stm32,stm32f103xx
+
+package machine
+
+// Peripheral abstraction layer for the stm32.
+
+import (
+	"device/arm"
+	"device/stm32"
+)
+
+const CPU_FREQUENCY = 72000000
+
+const (
+	GPIO_INPUT        = 0 // Input mode
+	GPIO_OUTPUT_10MHz = 1 // Output mode, max speed 10MHz
+	GPIO_OUTPUT_2MHz  = 2 // Output mode, max speed 2MHz
+	GPIO_OUTPUT_50MHz = 3 // Output mode, max speed 50MHz
+	GPIO_OUTPUT       = GPIO_OUTPUT_2MHz
+
+	GPIO_INPUT_MODE_ANALOG       = 0  // Input analog mode
+	GPIO_INPUT_MODE_FLOATING     = 4  // Input floating mode
+	GPIO_INPUT_MODE_PULL_UP_DOWN = 8  // Input pull up/down mode
+	GPIO_INPUT_MODE_RESERVED     = 12 // Input mode (reserved)
+
+	GPIO_OUTPUT_MODE_GP_PUSH_PULL   = 0  // Output mode general purpose push/pull
+	GPIO_OUTPUT_MODE_GP_OPEN_DRAIN  = 4  // Output mode general purpose open drain
+	GPIO_OUTPUT_MODE_ALT_PUSH_PULL  = 8  // Output mode alt. purpose push/pull
+	GPIO_OUTPUT_MODE_ALT_OPEN_DRAIN = 12 // Output mode alt. purpose open drain
+)
+
+func (p GPIO) getPort() *stm32.GPIO_Type {
+	switch p.Pin / 16 {
+	case 0:
+		return stm32.GPIOA
+	case 1:
+		return stm32.GPIOB
+	case 2:
+		return stm32.GPIOC
+	case 3:
+		return stm32.GPIOD
+	case 4:
+		return stm32.GPIOE
+	case 5:
+		return stm32.GPIOF
+	case 6:
+		return stm32.GPIOG
+	default:
+		panic("machine: unknown port")
+	}
+}
+
+// enableClock enables the clock for this desired GPIO port.
+func (p GPIO) enableClock() {
+	switch p.Pin / 16 {
+	case 0:
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPAEN
+	case 1:
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPBEN
+	case 2:
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPCEN
+	case 3:
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPDEN
+	case 4:
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPEEN
+	case 5:
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPFEN
+	case 6:
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_IOPGEN
+	default:
+		panic("machine: unknown port")
+	}
+}
+
+// Configure this pin with the given configuration.
+func (p GPIO) Configure(config GPIOConfig) {
+	// Configure the GPIO pin.
+	p.enableClock()
+	port := p.getPort()
+	pin := p.Pin % 16
+	pos := p.Pin % 8 * 4
+	if pin < 8 {
+		port.CRL = stm32.RegValue((uint32(port.CRL) &^ (0xf << pos)) | (uint32(config.Mode) << pos))
+	} else {
+		port.CRH = stm32.RegValue((uint32(port.CRH) &^ (0xf << pos)) | (uint32(config.Mode) << pos))
+	}
+}
+
+// Set the pin to high or low.
+// Warning: only use this on an output pin!
+func (p GPIO) Set(high bool) {
+	port := p.getPort()
+	pin := p.Pin % 16
+	if high {
+		port.BSRR = 1 << pin
+	} else {
+		port.BSRR = 1 << (pin + 16)
+	}
+}
+
+// UART
+var (
+	// USART1 is the first hardware serial port on the STM32.
+	// Both UART0 and UART1 refers to USART1.
+	UART0 = &UART{}
+	UART1 = UART0
+)
+
+// Configure the UART.
+func (uart UART) Configure(config UARTConfig) {
+	// Default baud rate to 115200.
+	if config.BaudRate == 0 {
+		config.BaudRate = 115200
+	}
+
+	// pins
+	switch config.TX {
+	case PB6:
+		// use alternate TX/RX pins PB6/PB7 via AFIO mapping
+		stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_AFIOEN
+		stm32.AFIO.MAPR |= stm32.AFIO_MAPR_USART1_REMAP
+		GPIO{PB6}.Configure(GPIOConfig{Mode: GPIO_OUTPUT_50MHz + GPIO_OUTPUT_MODE_ALT_PUSH_PULL})
+		GPIO{PB7}.Configure(GPIOConfig{Mode: GPIO_INPUT_MODE_FLOATING})
+	default:
+		// use standard TX/RX pins PA9 and PA10
+		GPIO{PA9}.Configure(GPIOConfig{Mode: GPIO_OUTPUT_50MHz + GPIO_OUTPUT_MODE_ALT_PUSH_PULL})
+		GPIO{PA10}.Configure(GPIOConfig{Mode: GPIO_INPUT_MODE_FLOATING})
+	}
+
+	// Enable USART1 clock
+	stm32.RCC.APB2ENR |= stm32.RCC_APB2ENR_USART1EN
+
+	// Set baud rate
+	uart.SetBaudRate(config.BaudRate)
+
+	// Enable USART1 port.
+	stm32.USART1.CR1 = stm32.USART_CR1_TE | stm32.USART_CR1_RE | stm32.USART_CR1_RXNEIE | stm32.USART_CR1_UE
+
+	// Enable RX IRQ.
+	arm.EnableIRQ(stm32.IRQ_USART1)
+}
+
+// SetBaudRate sets the communication speed for the UART.
+func (uart UART) SetBaudRate(br uint32) {
+	divider := CPU_FREQUENCY / br
+	stm32.USART1.BRR = stm32.RegValue(divider)
+}
+
+// WriteByte writes a byte of data to the UART.
+func (uart UART) WriteByte(c byte) error {
+	stm32.USART1.DR = stm32.RegValue(c)
+
+	for (stm32.USART1.SR & stm32.USART_SR_TXE) == 0 {
+	}
+	return nil
+}
+
+//go:export USART1_IRQHandler
+func handleUART1() {
+	bufferPut(byte((stm32.USART1.DR & 0xFF)))
+}

src/machine/uart.go

@@ -1,4 +1,4 @@
-// +build avr nrf
+// +build avr nrf stm32
 
 package machine
 
@@ -6,6 +6,8 @@ import "errors"
 
 type UARTConfig struct {
 	BaudRate uint32
+	TX       uint8
+	RX       uint8
 }
 
 type UART struct {

src/runtime/runtime_stm32.go

@@ -2,14 +2,8 @@
 
 package runtime
 
-import (
-	"device/arm"
-)
-
 type timeUnit int64
 
-const tickMicros = 1 // TODO
-
 //go:export Reset_Handler
 func main() {
 	preinit()
@@ -17,18 +11,3 @@ func main() {
 	mainWrapper()
 	abort()
 }
-
-func putchar(c byte) {
-	// TODO
-}
-
-func sleepTicks(d timeUnit) {
-	// TODO: use a real timer here
-	for i := 0; i < int(d/535); i++ {
-		arm.Asm("")
-	}
-}
-
-func ticks() timeUnit {
-	return 0 // TODO
-}

src/runtime/runtime_stm32f103xx.go

@@ -0,0 +1,56 @@
+// +build stm32,stm32f103xx
+
+package runtime
+
+import (
+	"device/arm"
+	"device/stm32"
+	"machine"
+)
+
+const tickMicros = 1 // TODO
+
+func init() {
+	initCLK()
+	machine.UART0.Configure(machine.UARTConfig{})
+}
+
+func putchar(c byte) {
+	machine.UART0.WriteByte(c)
+}
+
+// initCLK sets clock to 72MHz using HSE 8MHz crystal w/ PLL X 9 (8MHz x 9 = 72MHz).
+func initCLK() {
+	stm32.FLASH.ACR |= stm32.FLASH_ACR_LATENCY_2 // Two wait states, per datasheet
+	stm32.RCC.CFGR |= stm32.RCC_CFGR_PPRE1_DIV_2 // prescale AHB1 = HCLK/2
+	stm32.RCC.CR |= stm32.RCC_CR_HSEON           // enable HSE clock
+
+	// wait for the HSEREADY flag
+	for (stm32.RCC.CR & stm32.RCC_CR_HSERDY) == 0 {
+	}
+
+	stm32.RCC.CFGR |= stm32.RCC_CFGR_PLLSRC   // set PLL source to HSE
+	stm32.RCC.CFGR |= stm32.RCC_CFGR_PLLMUL_9 // multiply by 9
+	stm32.RCC.CR |= stm32.RCC_CR_PLLON        // enable the PLL
+
+	// wait for the PLLRDY flag
+	for (stm32.RCC.CR & stm32.RCC_CR_PLLRDY) == 0 {
+	}
+
+	stm32.RCC.CFGR |= stm32.RCC_CFGR_SW_PLL // set clock source to pll
+
+	// wait for PLL to be CLK
+	for (stm32.RCC.CFGR & stm32.RCC_CFGR_SWS_PLL) == 0 {
+	}
+}
+
+func sleepTicks(d timeUnit) {
+	// TODO: use a real timer here
+	for i := 0; i < int(d/535); i++ {
+		arm.Asm("")
+	}
+}
+
+func ticks() timeUnit {
+	return 0 // TODO
+}