modbus

# run with: mix opto22
alias Modbus.Master
alias Modbus.Float

# opto22 learning center configured with script/opto22.otg
# the otg is for an R2 but seems to work for R1, EB1, and EB2
# digital points increment address by 4 per module and by 1 per point
# analog points increment address by 8 per module and by 2 per point

{:ok, master} = Master.start_link(ip: {10, 77, 0, 10}, port: 502)

# turn on 'alarm'
:ok = Master.exec(master, {:fc, 1, 4, 1})
# turn on 'outside light'
:ok = Master.exec(master, {:fc, 1, 5, 1})
# turn on 'inside light'
:ok = Master.exec(master, {:fc, 1, 6, 1})
# turn on 'freezer door status'
:ok = Master.exec(master, {:fc, 1, 7, 1})

:timer.sleep(400)

# turn off all digital outputs
:ok = Master.exec(master, {:fc, 1, 4, [0, 0, 0, 0]})

# read the 'emergency' switch
{:ok, [0]} = Master.exec(master, {:rc, 1, 8, 1})

# read the 'fuel level' knob (0 to 10,000)
{:ok, data} = Master.exec(master, {:rir, 1, 32, 2})
[_] = Float.from_be(data)

# write to the 'fuel display' (0 to 10,000)
data = Float.to_be([+5000.0])
:ok = Master.exec(master, {:phr, 1, 16, data})

:ok = Master.stop(master)