AT24CXX.h

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#ifndef AT24CXX_H
#define AT24CXX_H

#include "TWI.h"

#ifndef CHARBITS
#define CHARBITS 8
#endif

class AT24CXX : protected TWI::Device {
public:
  const uint16_t PAGE_MAX;

  const uint16_t PAGE_MASK;

  const size_t SIZE;

  AT24CXX(TWI& twi,
          uint8_t subaddr = 0,
          const size_t size = 32,
          const uint16_t page_max = 32) :
    TWI::Device(twi, 0x50 | (subaddr & 0x07)),
    PAGE_MAX(page_max),
    PAGE_MASK(page_max - 1),
    SIZE((size / CHARBITS) * 1024)
  {}

  bool is_ready()
  {
    if (!acquire()) return (false);
    int res = write(NULL);
    if (!release()) return (false);
    return (res == 0);
  }

  int read(void* dest, uint16_t src, size_t count)
  {
    uint8_t retry = RETRY_MAX;
    src = __builtin_bswap16(src);
    do {
      if (!acquire()) return (-1);
      int res = write(&src, sizeof(src));
      if (res == sizeof(src)) {
        res = read(dest, count);
        if (!release()) break;
        if (res == (int) count) return (res);
      }
      if (!release()) return (-1);
      delay(RETRY_DELAY_MS);
    } while (--retry);
    return (-1);
  }

  int write(uint16_t dest, const void* src, size_t count)
  {
    uint8_t* p = (uint8_t*) src;
    size_t s = count;
    size_t n = PAGE_MAX - (dest & PAGE_MASK);
    if (n > s) n = s;
    while (1) {
      uint8_t retry = RETRY_MAX;
      uint16_t addr = __builtin_bswap16(dest);
      iovec_t vec[3];
      iovec_t* vp = vec;
      int res = -1;
      iovec_arg(vp, &addr, sizeof(addr));
      iovec_arg(vp, p, n);
      iovec_end(vp);
      do {
        if (!acquire()) continue;
        res = write(vec);
        if (!release()) continue;
        if (res > 0) break;
        delay(RETRY_DELAY_MS);
      } while (--retry);
      if (res < 0) return (-1);
      s -= n;
      if (s == 0) return (count);
      dest += n;
      p += n;
      n = (s < PAGE_MAX ? s : PAGE_MAX);
    }
  }

  using TWI::Device::read;
  using TWI::Device::write;

private:
  static const uint8_t RETRY_MAX = 20;

  static const uint8_t RETRY_DELAY_MS = 1;
};

class AT24C32 : public AT24CXX {
public:
  AT24C32(TWI& twi, uint8_t subaddr = 0) :
    AT24CXX(twi, subaddr, 32, 32)
  {}
};

class AT24C64 : public AT24CXX {
public:
  AT24C64(TWI& twi, uint8_t subaddr = 0) :
    AT24CXX(twi, subaddr, 64, 32)
  {}
};

class AT24C128 : public AT24CXX {
public:
  AT24C128(TWI& twi, uint8_t subaddr = 0) :
    AT24CXX(twi, subaddr, 128, 64)
  {}
};

class AT24C256 : public AT24CXX {
public:
  AT24C256(TWI& twi, uint8_t subaddr = 0) :
    AT24CXX(twi, subaddr, 256, 64)
  {}
};

class AT24C512 : public AT24CXX {
public:
  AT24C512(TWI& twi, uint8_t subaddr = 0) :
    AT24CXX(twi, subaddr, 512, 128)
  {}
};
#endif