stm32 add SPI for stm32f4

src/machine/machine_stm32_spi.go

@@ -0,0 +1,99 @@
+// +build stm32
+
+package machine
+
+// Peripheral abstraction layer for SPI on the stm32 family
+
+import (
+	"device/stm32"
+	"unsafe"
+)
+
+// SPIConfig is used to store config info for SPI.
+type SPIConfig struct {
+	Frequency uint32
+	SCK       Pin
+	MOSI      Pin
+	MISO      Pin
+	LSBFirst  bool
+	Mode      uint8
+}
+
+// Configure is intended to setup the STM32 SPI1 interface.
+// Features still TODO:
+// - support SPI2 and SPI3
+// - allow setting data size to 16 bits?
+// - allow setting direction in HW for additional optimization?
+// - hardware SS pin?
+func (spi SPI) Configure(config SPIConfig) {
+	// enable clock for SPI
+	enableAltFuncClock(unsafe.Pointer(spi.Bus))
+
+	// Get SPI baud rate based on the bus speed it's attached to
+	var conf uint32 = spi.getBaudRate(config)
+
+	// set bit transfer order
+	if config.LSBFirst {
+		conf |= stm32.SPI_CR1_LSBFIRST
+	}
+
+	// set polarity and phase on the SPI interface
+	switch config.Mode {
+	case Mode0:
+		conf &^= (1 << stm32.SPI_CR1_CPOL_Pos)
+		conf &^= (1 << stm32.SPI_CR1_CPHA_Pos)
+	case Mode1:
+		conf &^= (1 << stm32.SPI_CR1_CPOL_Pos)
+		conf |= (1 << stm32.SPI_CR1_CPHA_Pos)
+	case Mode2:
+		conf |= (1 << stm32.SPI_CR1_CPOL_Pos)
+		conf &^= (1 << stm32.SPI_CR1_CPHA_Pos)
+	case Mode3:
+		conf |= (1 << stm32.SPI_CR1_CPOL_Pos)
+		conf |= (1 << stm32.SPI_CR1_CPHA_Pos)
+	default: // to mode 0
+		conf &^= (1 << stm32.SPI_CR1_CPOL_Pos)
+		conf &^= (1 << stm32.SPI_CR1_CPHA_Pos)
+	}
+
+	// set to SPI master
+	conf |= stm32.SPI_CR1_MSTR
+
+	// disable MCU acting as SPI slave
+	conf |= stm32.SPI_CR1_SSM | stm32.SPI_CR1_SSI
+
+	// now set the configuration
+	spi.Bus.CR1.Set(conf)
+
+	// init pins
+	if config.SCK == 0 && config.MOSI == 0 && config.MISO == 0 {
+		config.SCK = SPI0_SCK_PIN
+		config.MOSI = SPI0_MOSI_PIN
+		config.MISO = SPI0_MISO_PIN
+	}
+	spi.configurePins(config)
+
+	// enable SPI interface
+	spi.Bus.CR1.SetBits(stm32.SPI_CR1_SPE)
+}
+
+// Transfer writes/reads a single byte using the SPI interface.
+func (spi SPI) Transfer(w byte) (byte, error) {
+	// Write data to be transmitted to the SPI data register
+	spi.Bus.DR.Set(uint32(w))
+
+	// Wait until transmit complete
+	for !spi.Bus.SR.HasBits(stm32.SPI_SR_TXE) {
+	}
+
+	// Wait until receive complete
+	for !spi.Bus.SR.HasBits(stm32.SPI_SR_RXNE) {
+	}
+
+	// Wait until SPI is not busy
+	for spi.Bus.SR.HasBits(stm32.SPI_SR_BSY) {
+	}
+
+	// Return received data from SPI data register
+	return byte(spi.Bus.DR.Get()), nil
+}