127 lines
2.3 KiB
C++
127 lines
2.3 KiB
C++
#pragma once
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#include <stdint.h>
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#include <util/twi.h>
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namespace i2c {
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#if defined(__AVR_ATmega1284P__) || defined(__AVR_ATmega328P__)
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template <uint32_t Clock>
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class Hardware {
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public:
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static void init()
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{
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constexpr auto clock = calcClock();
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static_assert(checkClock(clock), "Unable to set requested I2C frequency");
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TWSR = clock.prescaler;
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TWBR = clock.bitrate;
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}
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template <uint8_t Addr>
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static bool start(bool read)
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{
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TWCR = (1 << TWINT) | (1 << TWSTA) | (1 << TWEN);
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while (!(TWCR & (1 << TWINT)))
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;
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uint8_t status = TW_STATUS & 0xF8;
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if (status != TW_START && status != TW_REP_START)
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return false;
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TWDR = (Addr << 1) | read;
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TWCR = (1 << TWINT) | (1 << TWEN);
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while (!(TWCR & (1 << TWINT)))
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;
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status = TW_STATUS & 0xF8;
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if (status != TW_MT_SLA_ACK && status != TW_MR_SLA_ACK)
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return false;
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return true;
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}
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static bool write(uint8_t data)
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{
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TWDR = data;
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TWCR = (1 << TWINT) | (1 << TWEN);
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while (!(TWCR & (1 << TWINT)))
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;
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uint8_t status = TW_STATUS & 0xF8;
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if (status != TW_MT_DATA_ACK)
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return false;
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return true;
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}
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template <bool LastByte = false>
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static uint8_t read()
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{
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TWCR = (1 << TWINT) | (1 << TWEN) | (!LastByte << TWEA);
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while (!(TWCR & (1 << TWINT)))
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;
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return TWDR;
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}
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static void stop()
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{
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TWCR = (1 << TWINT) | (1 << TWEN) | (1 << TWSTO);
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while (TWCR & (1 << TWSTO))
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;
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}
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private:
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struct ClockCfg {
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uint8_t prescaler;
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uint8_t bitrate;
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};
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static constexpr auto calcScl(ClockCfg clk)
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{
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return F_CPU / (16 + 2 * clk.bitrate * clk.prescaler);
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}
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static constexpr auto checkClock(ClockCfg clk)
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{
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constexpr auto constexprAbs = [](auto val) {
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if (val < 0)
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return -val;
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return val;
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};
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constexpr auto CLOCK_EPSILON = 10;
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auto scl = calcScl(clk);
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if (constexprAbs(static_cast<int>(scl) - static_cast<int>(Clock)) < CLOCK_EPSILON)
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return true;
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return false;
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}
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static constexpr auto calcClock()
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{
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constexpr auto calcBitRate = [](uint8_t prescaler) { return (F_CPU / Clock - 16) / (2 * prescaler); };
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auto clk = ClockCfg{1, 0};
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for (uint8_t prescaler = 1; prescaler <= 64; prescaler *= 4) {
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clk.prescaler = prescaler;
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clk.bitrate = calcBitRate(prescaler);
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if (checkClock(clk))
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break;
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}
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return clk;
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}
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};
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#endif
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} // namespace i2c
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