sda = 23 -- pins as on Adafruit Huzzah32 silkscreen
scl = 22
id = i2c.HW0 -- hardware interface
speed = i2c.SLOW

-- values for TCA9534A
i2c_addr = 0x3F

-- initialize i2c software interface
i2c.setup(id, sda, scl, speed)

port_input = 0x00
port_output = 0x01
reg_polarity = 0x02
reg_config = 0x03

function write_reg(addr, reg, data, callback)
   i2c.start(id)
   i2c.address(id, dev_address, i2c.TRANSMITTER)
   i2c.write(id, reg, data, true)
   i2c.stop(id)
   return i2c.transfer(id, callback, 5000)
end

function read_reg(dev_address, dev_register, callback)
  i2c.start(id)
  i2c.address(id, dev_address, i2c.TRANSMITTER)
  i2c.write(id, dev_register)
  i2c.start(id) -- repeated start condition
  i2c.address(id, dev_address, i2c.RECEIVER)
  i2c.read(id, 1)
  i2c.stop(id)
  return i2c.transfer(id, callback, 5000)
end

write_reg(i2c_addr, reg_config, 0x00, function(_,_) print("8-mosfet: reg_config done") end)

function set_mosfet(value)
   write_reg(i2c_addr, reg_config, value, function(_,a)
		print("set mosfet")
   end)
end

mosfet_value = 0xFF
function publish_status(value)
   mosfet_value = read_reg(i2c_addr, reg_output)
   for i = 0,8 do
      oskar_m:publish("/shannon/kontrol/relay/"..i, bit.band(bit.rshift(mosfet_value, i), 0x1), 0, 0)
   end
end

oskar_topichandle["/shannon/kontrol/relay"] = function (client, topic, data)
   n = tonumber(string.sub(topic, -1))
   if n<8 and n>=0 then
      if data then mosfet_value = bit.band(mosfet_value, bit.lshift(1, n))
      else mosfet_value = bit.bor(mosfet_value, bit.bnot(bit.lshift(1, n))) end
      set_mosfet(mosfet_value)
   end
end