uart/hardware.hpp

#pragma once

#define FORCE_INLINE __attribute__((always_inline))

namespace uart {

enum class Mode {
	ASYNCHRONOUS,
	ASYNCHRONOUS_2X,
	SYNCHRONOUS_MASTER,
	SYNCHRONOUS_SLAVE,
	SPI,
};

enum class Driven {
	INTERRUPT,
	BLOCKING,
};

namespace detail {

template <class Registers, typename CtrlFlagsA, typename CtrlFlagsB, typename CtrlFlagsC, class cfg, Mode mode>
class Hardware {
  public:
	static void init() FORCE_INLINE
	{
		constexpr auto baudVal = calcBaud();

		*Registers::BAUD_REG_H = static_cast<uint8_t>(baudVal >> 8);
		*Registers::BAUD_REG_L = static_cast<uint8_t>(baudVal);

		constexpr auto dataBitsVal = calcDataBits();
		constexpr auto parityVal = calcParity();
		constexpr auto stopBitsVal = calcStopBits();
		constexpr auto modeVal = calcMode();
		constexpr auto enableRx = calcRxState<true>();
		constexpr auto enableTx = calcTxState<true>();

		constexpr uint8_t controlRegB = dataBitsVal.regBVal | enableRx | enableTx;
		constexpr uint8_t controlRegC = dataBitsVal.regCVal | parityVal | stopBitsVal | modeVal;

		*Registers::CTRL_STAT_REG_B = controlRegB;
		*Registers::CTRL_STAT_REG_C = controlRegC;
	}

	static void txByte(typename cfg::data_t byte) FORCE_INLINE
	{
		while (!(*Registers::CTRL_STAT_REG_A & (1 << CtrlFlagsA::DATA_REG_EMPTY)))
			;

		*Registers::IO_REG = byte;
	}

  private:
	struct DataBitsVal {
		uint8_t regCVal = 0;
		uint8_t regBVal = 0;
	};

	static constexpr auto calcBaud()
	{
		// The actual formula is (F_CPU / (16 * baudRate)) - 1, but this one has the advantage of rounding correctly
		constexpr auto baudVal = (F_CPU + 8 * cfg::BAUD_RATE) / (16 * cfg::BAUD_RATE) - 1;
		return baudVal;
	}

	static constexpr auto calcDataBits()
	{
		DataBitsVal dataBitsVal;

		switch (cfg::DATA_BITS) {
		case DataBits::FIVE:
			dataBitsVal.regCVal = 0;
			break;
		case DataBits::SIX:
			dataBitsVal.regCVal = (1 << CtrlFlagsC::CHAR_SIZE_0);
			break;
		case DataBits::SEVEN:
			dataBitsVal.regCVal = (1 << CtrlFlagsC::CHAR_SIZE_1);
			break;
		case DataBits::EIGHT:
			dataBitsVal.regCVal = (1 << CtrlFlagsC::CHAR_SIZE_1) | (1 << CtrlFlagsC::CHAR_SIZE_0);
			break;
		case DataBits::NINE:
			dataBitsVal.regCVal = (1 << CtrlFlagsC::CHAR_SIZE_1) | (1 << CtrlFlagsC::CHAR_SIZE_0);
			dataBitsVal.regBVal = (1 << CtrlFlagsB::CHAR_SIZE_2);
			break;
		}

		return dataBitsVal;
	}

	static constexpr auto calcParity()
	{
		uint8_t parityVal = 0;

		if (cfg::PARITY == Parity::EVEN)
			parityVal = (1 << CtrlFlagsC::PARITY_MODE_1);
		else if (cfg::PARITY == Parity::ODD)
			parityVal = (1 << CtrlFlagsC::PARITY_MODE_1) | (1 << CtrlFlagsC::PARITY_MODE_0);

		return parityVal;
	}

	static constexpr auto calcStopBits()
	{
		uint8_t stopBitsVal = 0;

		if (cfg::STOP_BITS == StopBits::TWO)
			stopBitsVal = (1 << CtrlFlagsC::STOP_BIT_SEL);

		return stopBitsVal;
	}

	static constexpr auto calcMode()
	{
		static_assert(mode != Mode::SPI, "SPI mode can not be used with uart");

		uint8_t modeVal = 0;

		if (mode == Mode::SYNCHRONOUS_MASTER || mode == Mode::SYNCHRONOUS_SLAVE) {
			modeVal = (1 << CtrlFlagsC::MODE_SEL_0);
		}

		return modeVal;
	}

	template <bool enable>
	static constexpr auto calcRxState()
	{
		uint8_t enableVal = 0;

		if (enable)
			enableVal = (1 << CtrlFlagsB::RX_ENABLE);

		return enableVal;
	}

	template <bool enable>
	static constexpr auto calcTxState()
	{
		uint8_t enableVal = 0;

		if (enable)
			enableVal = (1 << CtrlFlagsB::TX_ENABLE);

		return enableVal;
	}
};

} // namespace detail

} // namespace uart

#undef FORCE_INLINE