-- John Longworth December 2017
-- Read time from an external RTC
-- Uses I2C module
-- NOTE: time is stored in BCD format

local id, sda, scl, device = 0, 3, 4, 0x68
i2c.setup(id, sda, scl, i2c.SLOW)

i2c.start(id)
i2c.address(id, device, i2c.TRANSMITTER)
i2c.write(id, 0)
i2c.stop(id)
i2c.start(id)
i2c.address(id, device, i2c.RECEIVER)
c = i2c.read(id, 7)  -- Read 7 bytes of data
i2c.stop(id)

print(" hr "..string.format("%X",string.byte(c, 3)),
      "min "..string.format("%X",string.byte(c, 2)),
      "sec "..string.format("%X",string.byte(c, 1)))
print("Day No "..string.format("%X",string.byte(c, 4)))
print("day", string.format("%X",string.byte(c, 5)))
print("mnt", string.format("%X",string.byte(c, 6)))
print(" yr", string.format("%X",string.byte(c, 7)))