Main.swift

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift open source project
//
// Copyright (c) 2023 Apple Inc. and the Swift project authors.
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
//
//===----------------------------------------------------------------------===//

enum STM32F746Board {
  static func initialize() {
    // Configure pin I1 as an LED

    // (1) AHB1ENR[i] = 1 ... enable clock
    setRegisterBit(
      baseAddress: RCC.BaseAddress, offset: RCC.Offsets.AHB1ENR, bit: 8,
      value: 1)
    // (2) MODER[1] = 1 ... set mode to output
    setRegisterTwoBitField(
      baseAddress: GPIO.GPIOi_BaseAddress, offset: GPIO.Offsets.MODER,
      bitsStartingAt: 2, value: 1)
    // (3) OTYPER[1] = 0 ... output type is push-pull
    setRegisterBit(
      baseAddress: GPIO.GPIOi_BaseAddress, offset: GPIO.Offsets.OTYPER, bit: 1,
      value: 0)
    // (4) OSPEEDR[1] = 2 ... speed is high
    setRegisterTwoBitField(
      baseAddress: GPIO.GPIOi_BaseAddress, offset: GPIO.Offsets.OSPEEDR,
      bitsStartingAt: 2, value: 2)
    // (5) PUPDR[1] = 2 ... set pull to down
    setRegisterTwoBitField(
      baseAddress: GPIO.GPIOi_BaseAddress, offset: GPIO.Offsets.PUPDR,
      bitsStartingAt: 2, value: 2)

    ledOff()
  }

  static func ledOn() {
    // ODR[1] = 1
    setRegisterBit(
      baseAddress: GPIO.GPIOi_BaseAddress, offset: GPIO.Offsets.ODR, bit: 1,
      value: 1)
  }

  static func ledOff() {
    // ODR[1] = 0
    setRegisterBit(
      baseAddress: GPIO.GPIOi_BaseAddress, offset: GPIO.Offsets.ODR, bit: 1,
      value: 0)
  }

  static func delay(milliseconds: Int) {
    for _ in 0..<10_000 * milliseconds {
      nop()
    }
  }
}

@main
struct Main {
  typealias Board = STM32F746Board

  static func main() {
    Board.initialize()

    while true {
      Board.ledOn()
      Board.delay(milliseconds: 100)
      Board.ledOff()
      Board.delay(milliseconds: 300)
    }
  }
}