Reading battery capacity nodeMCU - lua

battery_capacity_nodemcu

id=0
-- represent actually PIN on nodeMCU such as 
-- D7 and D5 in this case
-- GND needs to be connected
sda=7   -- GPIO13
scl=5   -- GPIO14

    -- initialize i2c, set pin1 as sda, set pin2 as scl
    i2c.setup(id,sda,scl,i2c.SLOW)

    -- user defined function: read from reg_addr content of dev_addr
    function read_reg(dev_addr, reg_addr)
      i2c.start(id)
      a = i2c.address(id, dev_addr ,i2c.TRANSMITTER)
      print(a)
      i2c.write(id,reg_addr)
      i2c.stop(id)
      i2c.start(id)
      i2c.address(id, dev_addr,i2c.RECEIVER)
      c=i2c.read(id,1)
      i2c.stop(id)
      return c
    end

    -- get content of register 0x0d (13) of device 0x0B (11)
     reg = read_reg(0x0B, 0x0d)
     print("Battery capacity: " , string.byte(reg))