Elixir Serial Port with Modbus RTU.

1. Add baud to your list of dependencies in mix.exs:

def deps do
  [{:baud, "~> MAJOR.MINOR"}]
end

2. Enumerate your serial ports.

["COM1", "/dev/ttyUSB0", "/dev/tty.usbserial-FTVFV143"] = Baud.Enum.list()

3. Interact with your serial port.

# this echo sample requires a loopback plug
tty =
  case :os.type() do
    {:unix, :darwin} -> "/dev/tty.usbserial-FTYHQD9MA"
    {:unix, :linux} -> "/dev/ttyUSB0"
    {:win32, :nt} -> "COM5"
  end

{:ok, pid} = Baud.start_link(device: tty)

Baud.write(pid, "01234\n56789\n98765\n43210")
{:ok, "01234\n"} = Baud.readln(pid)
{:ok, "56789\n"} = Baud.readln(pid)
{:ok, "98765\n"} = Baud.readln(pid)
{:to, "43210"} = Baud.readln(pid)

Baud.write(pid, "01234\r56789\r98765\r43210")
{:ok, "01234\r"} = Baud.readcr(pid)
{:ok, "56789\r"} = Baud.readcr(pid)
{:ok, "98765\r"} = Baud.readcr(pid)
{:to, "43210"} = Baud.readcr(pid)

Baud.write(pid, "01234\n56789\n98765\n43210")
{:ok, "01234\n"} = Baud.readn(pid, 6)
{:ok, "56789\n"} = Baud.readn(pid, 6)
{:ok, "98765\n"} = Baud.readn(pid, 6)
{:to, "43210"} = Baud.readn(pid, 6)
{:ok, ""} = Baud.readn(pid, 0)

Baud.write(pid, "01234\n")
Baud.write(pid, "56789\n")
Baud.write(pid, "98765\n")
Baud.write(pid, "43210")
:timer.sleep(100)
{:ok, "01234\n56789\n98765\n43210"} = Baud.readall(pid)

Baud.stop(pid)

4. Connect the RTU master to the testing RTU slave:

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

tty0 =
  case :os.type() do
    {:unix, :darwin} -> "/dev/tty.usbserial-FTYHQD9MA"
    {:unix, :linux} -> "/dev/ttyUSB0"
    {:win32, :nt} -> "COM5"
  end

tty1 =
  case :os.type() do
    {:unix, :darwin} -> "/dev/tty.usbserial-FTYHQD9MB"
    {:unix, :linux} -> "/dev/ttyUSB1"
    {:win32, :nt} -> "COM6"
  end

# 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, device: tty0, speed: 115_200)
{:ok, master} = Master.start_link(device: tty1, speed: 115_200)

# 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)

# test with socat ttys
./test.sh
# test with custom ttys (null modem)
export TTY0="/dev/ttyUSB0"
export TTY1="/dev/ttyUSB1"
mix test
#in Windows
#requires COM98/COM99 com0com ports
test.bat

Install Visual C++ 2015 Build Tools by one of the following methods:

• Download and install visualcppbuildtools_full.exe
• Thru Chocolatey choco install VisualCppBuildTools.

From the Windows run command launch cmd /K c:\Users\samuel\Desktop\baud\setenv.bat adjusting your code location accordingly.

Give yourself access to serial ports with sudo gpasswd -s samuel dialout. Follow the official Elixir installation instructions and install build-essential erlang-dev as well.

Give yourself access to serial ports with sudo dseditgroup -o edit -a samuel -t user wheel.

Future

• Remote compile mix task to Linux & Windows

0.6.1

• Added test.bat for Windows com0com ports

0.6.0

• Using now the transport and protocol behaviors defined in modbus package

0.5.7

• Updated to sniff 0.1.7
• Updated to modbus 0.3.9
• Added RTU slave for testability
• Master module rewrite for readability
• Baud module rewrite for readability

0.5.6

• Updated to sniff 0.1.6 (bug fix)
• Test with fake socat ttys
• Full posix tty paths required
• Pass test serial port thru environment variables

0.5.4

• Updated to sniff 0.1.4

0.5.3

• Updated to sniff 0.1.3
• Document Windows/Ubuntu dependencies

0.5.2

• Updated to sniff 0.1.2 need for ´iex -S mix´ to find native library in Elixir 1.5.1
• Updated to modbus 0.3.7

0.5.1

• Updated to sniff 0.1.1
• Extract NIF to its own repo (sniff)

0.5.0

• Posix NIF implementation
• Win32 NIF implementation
• Baud api simplification
• Refactored to NIF for improved speed and test isolation
• Removed sock/loop (will be implemented as part of forward)

0.4.3

• Add wait4ch to handle non standard line/packet terminators

0.4.2

• Port proxy added to ensure proper closing on exit status msg
• Kill tests added for both baud and sock
• Refactored from genserver to actor

0.4.1

• Updated Makefile for Windows 10

0.4.0

• Added sample script (1 y 2)
• Improved documentation
• Update to modbus 0.2.0 (refactoring required)

0.3.0

• Integration test script for modport
• Added test.sh to isolate tests run
• RTU master, slave, and tcpgw loop modes
• Serial port export to socket in raw, text, and modbus mode
• RTU API matched to modbus package (1,2,3,4,5,6,15,16)
• Improved timeout handling for shorter test times

0.2.0

• Interactive RTU: read/write up to 8 coils at once

0.1.0

• Cross platform native serial port (mac, win, linux)
• Modbus (tcu-rtu), raw and text loop mode

• Support udoo neo
• Support beaglebone black
• Support raspberry pi 3 B
• Assess rewriting the windows native code using the win32 api
• Assess rewriting the windows native code using c#/.net
• Split into a core package and OS dependant packages holding native code
• loop* tests still show data corruption when run all at once
• Implement Modbus ASCII support (no available device)
• Implement DTR/RTS control and CTS/DSR monitoring
• Implement separate discard for input and output buffers
• Unit test 8N1 7E1 7O1 and baud rate setup against a confirmed gauge
• Get port names required for unit testing from environment variables
• Implement a clean exit to loop mode for a timely port close and to ensure test isolation
• Improve debugging: stderr messages are interlaced in mix test output
• Improve debugging: dev/test/prod conditional output
• Move from polling to overlapped on Windows
• Research why interchar timeout is applied when reading a single byte even having many already in the input buffer. Happens on MAC.
• Research how to bypass the 0.1s minimum granularity on posix systems
• Research higher baud rates support for posix and win32
• Research Mix unit test isolation (OS resources cleanup)
• Research printf to embed variable sized arrays as hex strings