Nucleo f722ze (#1526)

machine/nucleo-f722ze: Add support for ST Micro NUCLEO-F722ZE

src/machine/machine_stm32f7x2.go

@@ -0,0 +1,44 @@
+// +build stm32f7x2
+
+package machine
+
+// Peripheral abstraction layer for the stm32f407
+
+import (
+	"device/stm32"
+	"runtime/interrupt"
+)
+
+func CPUFrequency() uint32 {
+	return 216000000
+}
+
+//---------- UART related types and code
+
+// UART representation
+type UART struct {
+	Buffer          *RingBuffer
+	Bus             *stm32.USART_Type
+	Interrupt       interrupt.Interrupt
+	AltFuncSelector stm32.AltFunc
+}
+
+// Configure the UART.
+func (uart UART) configurePins(config UARTConfig) {
+	// enable the alternate functions on the TX and RX pins
+	config.TX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTTX}, uart.AltFuncSelector)
+	config.RX.ConfigureAltFunc(PinConfig{Mode: PinModeUARTRX}, uart.AltFuncSelector)
+}
+
+// UART baudrate calc based on the bus and clockspeed
+// NOTE: keep this in sync with the runtime/runtime_stm32f7x2.go clock init code
+func (uart UART) getBaudRateDivisor(baudRate uint32) uint32 {
+	var clock uint32
+	switch uart.Bus {
+	case stm32.USART1, stm32.USART6:
+		clock = CPUFrequency() / 2 // APB2 Frequency
+	case stm32.USART2, stm32.USART3, stm32.UART4, stm32.UART5:
+		clock = CPUFrequency() / 8 // APB1 Frequency
+	}
+	return clock / baudRate
+}