115 lines
2.9 KiB
C++
115 lines
2.9 KiB
C++
#pragma once
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#include "../clock.hpp"
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#include <type_traits>
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#include <utility>
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#include <cstdint>
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#include <avr/interrupt.h>
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#include "../io/io.hpp"
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#include "../util/util.hpp"
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namespace spi {
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template <typename Cfg>
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class Software {
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static constexpr double calcClockDelay()
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{
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constexpr auto staticClockCycles = 10;
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constexpr auto maxFrequency = F_CPU / staticClockCycles;
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static_assert(Cfg::FREQ <= maxFrequency, "SPI frequency not achievable using selected clock speed");
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constexpr auto staticDelay = (1.0 * 1000 * 1000 / maxFrequency);
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const auto delayUs = ((1.0 * 1000 * 1000 / Cfg::FREQ) - staticDelay) / 2;
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return (delayUs > 0 ? delayUs : 0);
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}
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public:
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static_assert(Cfg::BITS >= 1 && Cfg::BITS <= 64, "Word size must be in range [1-64]");
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// clang-format off
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using word_t = std::conditional_t<Cfg::BITS <= 8, std::uint8_t,
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std::conditional_t<Cfg::BITS <= 16, std::uint16_t,
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std::conditional_t<Cfg::BITS <= 32, std::uint32_t,
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std::uint64_t>>>;
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// clang-format on
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static void init()
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{
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sm_sck = ((Cfg::MODE == Mode::MODE_0 || Cfg::MODE == Mode::MODE_1) ? false : true);
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sm_ss = true;
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sm_sck.dir(io::Dir::OUT);
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sm_miso.dir(io::Dir::IN);
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sm_miso.pullup(Cfg::PULLUP);
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sm_mosi.dir(io::Dir::OUT);
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sm_ss.dir(io::Dir::OUT);
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}
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static word_t transfer(const word_t data)
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{
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const auto oldInterruptState = disableInterrupts();
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auto dataIn = word_t{};
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util::for_constexpr(
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[&](const auto idx) {
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constexpr auto i = idx.value;
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constexpr auto bitPos = (Cfg::BIT_ORDER == BitOrder::MSB_FIRST ? Cfg::BITS - i - 1 : i);
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if constexpr (Cfg::MODE == Mode::MODE_0 || Cfg::MODE == Mode::MODE_2) {
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sm_mosi = data >> bitPos & 1;
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_delay_us(DELAY_US);
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sm_sck.toggle();
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const auto receivedBit = sm_miso.read();
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dataIn |= word_t{receivedBit} << bitPos;
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_delay_us(DELAY_US);
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sm_sck.toggle();
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} else {
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sm_sck.toggle();
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sm_mosi = data >> bitPos & 1;
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_delay_us(DELAY_US);
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sm_sck.toggle();
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const auto receivedBit = sm_miso.read();
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dataIn |= word_t{receivedBit} << bitPos;
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_delay_us(DELAY_US);
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}
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},
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std::make_index_sequence<Cfg::BITS>{});
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enableInterrupts(oldInterruptState);
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return dataIn;
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}
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static void select(const bool selectState)
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{
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sm_ss = !selectState;
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}
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private:
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static io::Pin<Cfg::SCK_PIN> sm_sck;
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static io::Pin<Cfg::MISO_PIN> sm_miso;
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static io::Pin<Cfg::MOSI_PIN> sm_mosi;
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static io::Pin<Cfg::SS_PIN> sm_ss;
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static constexpr auto DELAY_US = calcClockDelay();
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static inline std::uint8_t disableInterrupts()
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{
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const auto oldInterruptState = SREG;
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cli();
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return oldInterruptState;
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}
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static inline void enableInterrupts(const std::uint8_t oldInterruptState)
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{
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SREG = oldInterruptState;
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}
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};
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} // namespace spi
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