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//go:build stm32
package machine
// Peripheral abstraction layer for UARTs on the stm32 family.
import (
"device/stm32"
"runtime/interrupt"
"runtime/volatile"
"unsafe"
)
// UART representation
type UART struct {
Buffer *RingBuffer
Bus *stm32.USART_Type
Interrupt interrupt.Interrupt
TxAltFuncSelector uint8
RxAltFuncSelector uint8
// Registers specific to the chip
rxReg *volatile.Register32
txReg *volatile.Register32
statusReg *volatile.Register32
txEmptyFlag uint32
}
// Configure the UART.
func (uart *UART) Configure(config UARTConfig) {
// Default baud rate to 115200.
if config.BaudRate == 0 {
config.BaudRate = 115200
}
// Set the GPIO pins to defaults if they're not set
if config.TX == 0 && config.RX == 0 {
config.TX = UART_TX_PIN
config.RX = UART_RX_PIN
}
// STM32 families have different, but compatible, registers for
// basic UART functions. For each family populate the registers
// into `uart`.
uart.setRegisters()
// Enable USART clock
enableAltFuncClock(unsafe.Pointer(uart.Bus))
uart.configurePins(config)
// Set baud rate
uart.SetBaudRate(config.BaudRate)
// Enable USART port, tx, rx and rx interrupts
uart.Bus.CR1.Set(stm32.USART_CR1_TE | stm32.USART_CR1_RE | stm32.USART_CR1_RXNEIE | stm32.USART_CR1_UE)
// Enable RX IRQ
uart.Interrupt.SetPriority(0xc0)
uart.Interrupt.Enable()
}
// handleInterrupt should be called from the appropriate interrupt handler for
// this UART instance.
func (uart *UART) handleInterrupt(interrupt.Interrupt) {
uart.Receive(byte((uart.rxReg.Get() & 0xFF)))
}
// SetBaudRate sets the communication speed for the UART. Defer to chip-specific
// routines for calculation
func (uart *UART) SetBaudRate(br uint32) {
divider := uart.getBaudRateDivisor(br)
uart.Bus.BRR.Set(divider)
}
// WriteByte writes a byte of data to the UART.
func (uart *UART) WriteByte(c byte) error {
uart.txReg.Set(uint32(c))
for !uart.statusReg.HasBits(uart.txEmptyFlag) {
}
return nil
}
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