modbus v0.3.0 Modbus.Master

TCP Master server.

Example

alias Modbus.Master

# opto22 rack configured as follows
# m0 - 4p digital input
#  p0 - 24V
#  p1 - 0V
#  p2 - m1.p2
#  p3 - m1.p3
# m1 - 4p digital output
#  p0 - NC
#  p1 - NC
#  p2 - m0.p2
#  p3 - m0.p3
# m2 - 2p analog input (-10V to +10V)
#  p0 - m3.p0
#  p1 - m3.p1
# m3 - 2p analog output (-10V to +10V)
#  p0 - m2.p0
#  p1 - m2.p1

{:ok, pid} = Master.start_link([ip: {10,77,0,2}, port: 502])

#turn off m1.p0
:ok = Master.tcp(pid, {:fc, 1, 4, 0})
#turn on m1.p1
:ok = Master.tcp(pid, {:fc, 1, 5, 1})
#alternate m1.p2 and m1.p3
:ok = Master.tcp(pid, {:fc, 1, 6, [1, 0]})

#write -5V (IEEE 754 float) to m3.p0
:ok = Master.tcp(pid, {:phr, 1, 24, [0xc0a0, 0x0000]})
#write +5V (IEEE 754 float) to m3.p1
:ok = Master.tcp(pid, {:phr, 1, 26, [0x40a0, 0x0000]})

:timer.sleep(20) #outputs settle delay

#read previous coils as inputs
{:ok, [0, 1, 1, 0]} = Master.tcp(pid, {:ri, 1, 4, 4})

#read previous analog channels as input registers
{:ok, [0xc0a0, 0x0000, 0x40a0, 0x0000]} = Master.tcp(pid, {:rir, 1, 24, 4})

Summary

Functions

Starts the Server

Stops the Server

Executes a Modbus TCP command

Functions

start_link(params, opts \\ [])

Starts the Server.

state is a keyword list where: ip is the internet address to connect to. port is the tcp port number to connect to. timeout is the connection timeout.

Returns {:ok, pid}.

Example

Modbus.Master.start_link([ip: {10,77,0,2}, port: 502, timeout: 2000])
stop(pid)

Stops the Server.

tcp(pid, cmd, timeout \\ 2000)

Executes a Modbus TCP 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]}.