Modbux v0.3.9 Modbux.Rtu.Slave View Source

API for a Modbus RTU Slave device.

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Functions

Returns a specification to start this module under a supervisor.

Gets the current state of the Slave DB.

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

Send a raw frame through the serial port.

Updates the state of the Slave DB.

Starts a Modbus RTU Slave process.

Gets the Slave state.

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Returns a specification to start this module under a supervisor.

See Supervisor.

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get_db(pid)

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get_db(atom() | pid() | {atom(), any()} | {:via, atom(), any()}) :: any()

Gets the current state of the Slave DB.

Invoked when the server is started. start_link/3 or start/3 will block until it returns.

init_arg is the argument term (second argument) passed to start_link/3.

Returning {:ok, state} will cause start_link/3 to return {:ok, pid} and the process to enter its loop.

Returning {:ok, state, timeout} is similar to {:ok, state}, except that it also sets a timeout. See the "Timeouts" section in the module documentation for more information.

Returning {:ok, state, :hibernate} is similar to {:ok, state} except the process is hibernated before entering the loop. See c:handle_call/3 for more information on hibernation.

Returning {:ok, state, {:continue, continue}} is similar to {:ok, state} except that immediately after entering the loop the c:handle_continue/2 callback will be invoked with the value continue as first argument.

Returning :ignore will cause start_link/3 to return :ignore and the process will exit normally without entering the loop or calling c:terminate/2. If used when part of a supervision tree the parent supervisor will not fail to start nor immediately try to restart the GenServer. The remainder of the supervision tree will be started and so the GenServer should not be required by other processes. It can be started later with Supervisor.restart_child/2 as the child specification is saved in the parent supervisor. The main use cases for this are:

  • The GenServer is disabled by configuration but might be enabled later.
  • An error occurred and it will be handled by a different mechanism than the Supervisor. Likely this approach involves calling Supervisor.restart_child/2 after a delay to attempt a restart.

Returning {:stop, reason} will cause start_link/3 to return {:error, reason} and the process to exit with reason reason without entering the loop or calling c:terminate/2.

Callback implementation for GenServer.init/1.

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raw_write(pid, data)

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raw_write(atom() | pid() | {atom(), any()} | {:via, atom(), any()}, any()) ::
  any()

Send a raw frame through the serial port.

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request(pid, cmd)

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request(atom() | pid() | {atom(), any()} | {:via, atom(), any()}, any()) ::
  any()

Updates the state of the Slave DB.

cmd is a 4 elements tuple, as follows:

  • {: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.
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start_link(params)

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start_link(keyword()) :: :ignore | {:error, any()} | {:ok, pid()}

Starts a Modbus RTU Slave process.

The following options are available:

  • tty - defines the serial port to spawn the Slave.
  • gen_opts - defines extra options for the Genserver OTP configuration.
  • uart_opts - defines extra options for the UART configuration (defaults:

    [speed: 115200, rx_framing_timeout: 1000]).
  • model - defines the DB initial state.
  • active - (true or false) enable/disable DB updates notifications (mailbox).

The messages (when active mode is true) have the following form:

{:modbus_rtu, {:slave_request, payload}}

or

{:modbus_rtu, {:slave_error, payload, reason}}

The following are some reasons:

  • :ecrc - corrupted message (invalid crc).
  • :einval - invalid function.
  • :eaddr - invalid memory address requested.

Model (DB)

The model or data base (DB) defines the slave memory map, the DB is defined by the following syntax:

%{slave_id => %{{memory_type, address_number} => value}}

where:

  • slave_id - specifies a unique unit address from 1 to 247.
  • memory_type - specifies the memory between:

    • :c - Discrete Output Coils.
    • :i - Discrete Input Contacts.
    • :ir - Analog Input Registers.
    • :hr - Analog Output Registers.
  • address_number - specifies the memory address.
  • value - the current value from that memory.

Example

model = %{80 => %{{:c, 20818} => 0, {:hr, 20818} => 0}}
Modbux.Tcp.Server.start_link(model: model, port: 2000)
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state(pid)

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state(atom() | pid() | {atom(), any()} | {:via, atom(), any()}) :: any()

Gets the Slave state.

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stop(pid)

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stop(atom() | pid() | {atom(), any()} | {:via, atom(), any()}) :: :ok