modbus v0.4.0

Modbus.Master (modbus v0.4.0)

Modbus Master.

Example 

# run with: mix slave
alias Modbus.Slave
alias Modbus.Master

# start your slave with a shared model
model = %{
0x50 => %{
  {:c, 0x5152} => 0,
  {:i, 0x5354} => 0,
  {:i, 0x5355} => 1,
  {:hr, 0x5657} => 0x6162,
  {:ir, 0x5859} => 0x6364,
  {:ir, 0x585A} => 0x6566
}
}

{:ok, slave} = Slave.start_link(model: model)
# get the assigned tcp port
port = Slave.port(slave)

# interact with it
{:ok, master} = Master.start_link(ip: {127, 0, 0, 1}, port: port)

# read input
{:ok, [0, 1]} = Master.exec(master, {:ri, 0x50, 0x5354, 2})
# read input registers
{:ok, [0x6364, 0x6566]} = Master.exec(master, {:rir, 0x50, 0x5859, 2})

# toggle coil and read it back
:ok = Master.exec(master, {:fc, 0x50, 0x5152, 0})
{:ok, [0]} = Master.exec(master, {:rc, 0x50, 0x5152, 1})
:ok = Master.exec(master, {:fc, 0x50, 0x5152, 1})
{:ok, [1]} = Master.exec(master, {:rc, 0x50, 0x5152, 1})

# increment holding register and read it back
{:ok, [0x6162]} = Master.exec(master, {:rhr, 0x50, 0x5657, 1})
:ok = Master.exec(master, {:phr, 0x50, 0x5657, 0x6163})
{:ok, [0x6163]} = Master.exec(master, {:rhr, 0x50, 0x5657, 1})

:ok = Master.stop(master)
:ok = Slave.stop(slave)

Link to this section Summary

Functions

exec(master, cmd, timeout \\ 2000)

Executes a Modbus command.

start_link(opts)

Opens the connection.

stop(master)

Closes the connection.

Link to this section Functions

Link to this function

exec(master, cmd, timeout \\ 2000)

Executes a Modbus command.

cmd is one of:

  • {:rc, slave, address, count} read count coils.
  • {:ri, slave, address, count} read count inputs.
  • {:rhr, slave, address, count} read count holding registers.
  • {:rir, slave, address, count} read count input registers.
  • {:fc, slave, address, value} force single coil.
  • {:phr, slave, address, value} preset single holding register.
  • {:fc, slave, address, values} force multiple coils.
  • {:phr, slave, address, values} preset multiple holding registers.

Returns :ok | {:ok, [values]} | {:error, reason}.

Link to this function

start_link(opts)

Opens the connection.

opts is a keyword list where:

  • trans is the transport to use. Only the :tcp transport is available but other transports can be registered.
  • proto is the protocol to use. Available protocols are :tcp and :rtu. Defaults to :tcp.

The rest of options are passed verbatim to the transport constructor.

The following are the options needed by the default TCP transport.

  • ip is the internet address to connect to.
  • port is the tcp port number to connect to.
  • timeout is the optional connection timeout.

Returns {:ok, master} | {:error, reason}.

Example 

Modbus.Master.start_link(ip: {10,77,0,10}, port: 502, timeout: 2000)
Link to this function

stop(master)

Closes the connection.

Returns :ok | {:error, reason}.