defmodule Circuits.UART do
@moduledoc """
Find and use UARTs, serial ports, and more.
"""
use GenServer
alias Circuits.UART.Enumerator
# Many calls take timeouts for how long to wait for reading and writing
# serial ports. This is the additional time added to the GenServer message passing
# timeout so that the interprocess messaging timers don't hit before the
# timeouts on the actual operations.
@genserver_timeout_slack 500
# There's a timeout when interacting with the port as well. If the port
# doesn't respond by timeout + @port_timeout_slack, then there's something
# wrong with it.
@port_timeout_slack 400
defmodule State do
@moduledoc false
# port: C port process
# controlling_process: where events get sent
# name: port name when opened
# framing: framing behaviour
# framing_state: framing behaviour's state
# rx_framing_timeout: how long to wait for incomplete frames
# queued_messages: queued messages when in passive mode
# rx_framing_tref: frame completion timer
# is_active: active or passive mode
defstruct port: nil,
controlling_process: nil,
name: :closed,
framing: Circuits.UART.Framing.None,
framing_state: nil,
rx_framing_timeout: 0,
queued_messages: [],
rx_framing_tref: nil,
is_active: true,
id: :name
end
@type uart_option ::
{:active, boolean}
| {:speed, non_neg_integer}
| {:data_bits, 5..8}
| {:stop_bits, 1..2}
| {:parity, :none | :even | :odd | :space | :mark | :ignore}
| {:flow_control, :none | :hardware | :software}
| {:framing, module | {module, [term]}}
| {:rx_framing_timeout, integer}
| {:id, :name | :pid}
| {:rs485_enabled, boolean()}
| {:rs485_rts_on_send, boolean()}
| {:rs485_rts_after_send, boolean()}
| {:rs485_rx_during_tx, boolean()}
| {:rs485_terminate_bus, boolean()}
| {:rs485_delay_rts_before_send, pos_integer()}
| {:rs485_delay_rts_after_send, pos_integer()}
# Public API
@doc """
Return a map of available ports with information about each one. The map
looks like this:
```elixir
%{"ttyS0" -> %{vendor_id: 1234, product_id: 1,
manufacturer: "Acme Corporation", serial_number: "000001"},
"ttyUSB0" -> %{vendor_id: 1234, product_id: 2}}
```
Depending on the port and the operating system, not all fields may be
returned. Informational fields are:
* `:vendor_id` - The 16-bit USB vendor ID of the device providing the port. Vendor ID to name lists are managed through usb.org
* `:product_id` - The 16-bit vendor supplied product ID
* `:manufacturer` - The manufacturer of the port
* `:description` - A description or product name
* `:serial_number` - The device's serial number if it has one
"""
@spec enumerate() :: map()
defdelegate enumerate(), to: Enumerator
@doc """
Find UARTs.
This is intended as a diagnostic function for finding UARTs that you may have
opened and forgotten about. Since a UART can only be opened once, this helps
you find the problematic one so that you can close it.
It returns a list of {pid, uart_name} tuples.
NOTE: Do not rely on this function in production code. It may change if
updates to the interface make it more convenient to use.
"""
@spec find_pids() :: [{binary | :closed, pid()}]
def find_pids() do
Process.list()
|> Enum.filter(&is_circuits_uart_process/1)
|> Enum.map(&circuits_uart_info/1)
end
defp is_circuits_uart_process(pid) do
case Process.info(pid, :dictionary) do
{:dictionary, dictionary} ->
Keyword.get(dictionary, :"$initial_call") == {Circuits.UART, :init, 1}
_ ->
false
end
end
defp circuits_uart_info(pid) do
{name, _opts} = configuration(pid)
{pid, name}
end
@doc """
Start up a UART GenServer.
You usually don't need to pass options here unless you'd like to register a
name for the GenServer. See `open/3` for opening all of the configuration
options.
"""
@spec start_link(GenServer.options()) :: GenServer.on_start()
def start_link(opts \\ []) do
GenServer.start_link(__MODULE__, [], opts)
end
@doc """
Stop the UART GenServer.
"""
@spec stop(GenServer.server()) :: :ok
def stop(pid) do
GenServer.stop(pid)
end
@doc """
Open a serial port.
The following options are available:
* `:active` - (`true` or `false`) specifies whether data is received as
messages or by calling `read/2`. See discussion below.
* `:speed` - (number) set the initial baudrate (e.g., 115200)
* `:data_bits` - (5, 6, 7, 8) set the number of data bits (usually 8)
* `:stop_bits` - (1, 2) set the number of stop bits (usually 1)
* `:parity` - (`:none`, `:even`, `:odd`, `:space`, or `:mark`) set the
parity. Usually this is `:none`. Other values:
* `:space` means that the parity bit is always 0
* `:mark` means that the parity bit is always 1
* `:ignore` means that the parity bit is ignored (Linux/OSX only)
* `:flow_control` - (`:none`, `:hardware`, or `:software`) set the flow control
strategy.
* `:framing` - (`module` or `{module, args}`) set the framing for data.
The `module` must implement the `Circuits.UART.Framing` behaviour. See
`Circuits.UART.Framing.None`, `Circuits.UART.Framing.Line`, and
`Circuits.UART.Framing.FourByte`. The default is `Circuits.UART.Framing.None`.
* `:rx_framing_timeout` - (milliseconds) this specifies how long incomplete
frames will wait for the remainder to be received. Timed out partial
frames are reported as `{:partial, data}`. A timeout of <= 0 means to
wait forever.
* `:id` - (`:name` or `:pid`) specify what to return with the uart active
messages. with `:name` the messages are returned as `{:circuits_uart,
serial_port_name, data}` otherwise they are returned as `{:circuits_uart,
pid, data}`. The name and pid are the name of the connected UART or the pid
of the Circuits.UART server pid as returned by `start_link/1`. The default
value is `:name`.
The following options are supported on Linux only:
* `:rs485_enabled` - (`true` or `false`) enable RS485 mode.
* `:rs485_rts_on_send` - (`true` or `false`) enable RTS on send.
* `:rs485_rts_after_send` - (`true` or `false`) enable RTS after send.
* `:rs485_rx_during_tx` - (`true` or `false`) enable RX during TX (loopback).
* `:rs485_terminate_bus` - (`true` or `false`) enable bus termination.
* `:rs485_delay_rts_before_send` - (milliseconds) delay RTS before send.
* `:rs485_delay_rts_after_send` - (milliseconds) delay RTS after send.
Active mode defaults to true and means that data received on the UART is
reported in messages. The messages have the following form:
```elixir
{:circuits_uart, serial_port_id, data}
```
or
```elixir
{:circuits_uart, serial_port_id, {:error, reason}}
```
When in active mode, flow control can not be used to push back on the sender
and messages will accumulated in the mailbox should data arrive fast enough.
If this is an issue, set `:active` to false and call `read/2` manually when
ready for more data.
On success, `open/3` returns `:ok`. On error, `{:error, reason}` is returned.
The following are some reasons:
* `:enoent` - the specified port couldn't be found
* `:eagain` - the port is already open
* `:eacces` - permission was denied when opening the port
"""
@spec open(GenServer.server(), binary, [uart_option]) :: :ok | {:error, File.posix()}
def open(pid, name, opts \\ []) do
GenServer.call(pid, {:open, name, opts})
end
@doc """
Close the serial port. The GenServer continues to run so that a port can
be opened again.
"""
@spec close(GenServer.server()) :: :ok | {:error, File.posix()}
def close(pid) do
GenServer.call(pid, :close)
end
@doc """
Change the serial port configuration after `open/3` has been called. See
`open/3` for the valid options.
"""
@spec configure(GenServer.server(), [uart_option]) :: :ok | {:error, File.posix()}
def configure(pid, opts) do
GenServer.call(pid, {:configure, opts})
end
@doc """
Get the configuration of the serial port.
"""
@spec configuration(GenServer.server()) :: {binary() | :closed, [uart_option]}
def configuration(pid) do
GenServer.call(pid, :configuration)
end
@doc """
Send a continuous stream of zero bits for a duration in milliseconds.
By default, the zero bits are transmitted at least 0.25 seconds.
This is a convenience function for calling `set_break/2` to enable
the break signal, wait, and then turn it off.
"""
@spec send_break(GenServer.server(), integer) :: :ok | {:error, File.posix()}
def send_break(pid, duration \\ 250) do
:ok = set_break(pid, true)
:timer.sleep(duration)
set_break(pid, false)
end
@doc """
Start or stop sending a break signal.
"""
@spec set_break(GenServer.server(), boolean) :: :ok | {:error, File.posix()}
def set_break(pid, value) when is_boolean(value) do
GenServer.call(pid, {:set_break, value})
end
@doc """
Write data to the opened UART. It's possible for the write to return before all
of the data is actually transmitted. To wait for the data, call drain/1.
This call blocks until all of the data to be written is in the operating
system's internal buffers. If you're sending a lot of data on a slow link,
supply a longer timeout to avoid timing out prematurely.
Returns `:ok` on success or `{:error, reason}` if an error occurs.
Typical error reasons:
* `:ebadf` - the UART is closed
"""
@spec write(GenServer.server(), iodata(), non_neg_integer()) :: :ok | {:error, File.posix()}
def write(pid, data, timeout \\ 5000) do
GenServer.call(pid, {:write, data, timeout}, genserver_timeout(timeout))
end
@doc """
Read data from the UART. This call returns data as soon as it's available or
after timing out.
Returns `{:ok, binary}`, where `binary` is a binary data object that contains the
read data, `{:error, reason}` if an error occurs, or `{:ok, <<>>}` after timing out.
Typical error reasons:
* `:ebadf` - the UART is closed
* `:einval` - the UART is in active mode
"""
@spec read(GenServer.server(), non_neg_integer()) ::
{:ok, binary} | {:ok, {:partial, binary}} | {:error, File.posix()}
def read(pid, timeout \\ 5000) do
GenServer.call(pid, {:read, timeout}, genserver_timeout(timeout))
end
@doc """
Waits until all data has been transmitted. See
[tcdrain(3)](http://linux.die.net/man/3/tcdrain) for low level details on
Linux or OSX. This is not implemented on Windows.
"""
@spec drain(GenServer.server()) :: :ok | {:error, File.posix()}
def drain(pid) do
GenServer.call(pid, :drain)
end
@doc """
Flushes the `:receive` buffer, the `:transmit` buffer, or `:both`.
See [tcflush(3)](http://linux.die.net/man/3/tcflush) for low level details on
Linux or OSX. This calls `PurgeComm` on Windows.
"""
@spec flush(GenServer.server()) :: :ok | {:error, File.posix()}
def flush(pid, direction \\ :both) do
GenServer.call(pid, {:flush, direction})
end
@doc """
Returns a map of signal names and their current state (true or false).
Signals include:
* `:dsr` - Data Set Ready
* `:dtr` - Data Terminal Ready
* `:rts` - Request To Send
* `:st` - Secondary Transmitted Data
* `:sr` - Secondary Received Data
* `:cts` - Clear To Send
* `:cd` - Data Carrier Detect
* `:rng` - Ring Indicator
"""
@spec signals(GenServer.server()) :: map | {:error, File.posix()}
def signals(pid) do
GenServer.call(pid, :signals)
end
@doc """
Set or clear the Data Terminal Ready signal.
"""
@spec set_dtr(GenServer.server(), boolean) :: :ok | {:error, File.posix()}
def set_dtr(pid, value) when is_boolean(value) do
GenServer.call(pid, {:set_dtr, value})
end
@doc """
Set or clear the Request To Send signal.
"""
@spec set_rts(GenServer.server(), boolean) :: :ok | {:error, File.posix()}
def set_rts(pid, value) when is_boolean(value) do
GenServer.call(pid, {:set_rts, value})
end
@doc """
Change the controlling process that
receives events from an active uart.
"""
@spec controlling_process(GenServer.server(), pid) :: :ok | {:error, File.posix()}
def controlling_process(pid, controlling_process) when is_pid(controlling_process) do
GenServer.call(pid, {:controlling_process, controlling_process})
end
# gen_server callbacks
def init([]) do
executable = Application.app_dir(:circuits_uart, ["priv", "circuits_uart"]) |> to_charlist()
port =
Port.open({:spawn_executable, executable}, [
{:args, []},
{:packet, 2},
:use_stdio,
:binary,
:exit_status
])
state = %State{port: port}
{:ok, state}
end
def handle_call({:open, name, opts}, {from_pid, _}, state) do
new_framing = Keyword.get(opts, :framing, nil)
new_rx_framing_timeout = Keyword.get(opts, :rx_framing_timeout, state.rx_framing_timeout)
is_active = Keyword.get(opts, :active, true)
id_mode = Keyword.get(opts, :id, :name)
response = call_port(state, :open, {name, opts})
new_state =
change_framing(
%{
state
| name: name,
controlling_process: from_pid,
rx_framing_timeout: new_rx_framing_timeout,
is_active: is_active,
id: id_mode
},
new_framing
)
{:reply, response, new_state}
end
def handle_call(:configuration, _from, state) do
opts =
call_port(state, :configuration, {}) ++
[
active: state.is_active,
id: state.id,
rx_framing_timeout: state.rx_framing_timeout,
framing: state.framing
]
{:reply, {state.name, opts}, state}
end
def handle_call(:close, _from, state) do
# Clean up the C side
response = call_port(state, :close, nil)
# Clean up the Elixir side
new_framing_state = state.framing.flush(:both, state.framing_state)
new_state =
handle_framing_timer(
%{state | name: :closed, framing_state: new_framing_state, queued_messages: []},
:ok
)
{:reply, response, new_state}
end
def handle_call({:read, _timeout}, _from, %{queued_messages: [message | rest]} = state) do
# Return the queued response.
new_state = %{state | queued_messages: rest}
{:reply, {:ok, message}, new_state}
end
def handle_call({:read, timeout}, from, state) do
call_time = System.monotonic_time(:millisecond)
# Poll the serial port
case call_port(state, :read, timeout, port_timeout(timeout)) do
{:ok, <<>>} ->
# Timeout
{:reply, {:ok, <<>>}, state}
{:ok, buffer} ->
# More data
{rc, messages, new_framing_state} =
state.framing.remove_framing(buffer, state.framing_state)
new_state = handle_framing_timer(%{state | framing_state: new_framing_state}, rc)
if messages == [] do
# If nothing, poll some more with reduced timeout
elapsed = System.monotonic_time(:millisecond) - call_time
retry_timeout = max(timeout - elapsed, 0)
handle_call({:read, retry_timeout}, from, new_state)
else
# Return the first message
[first_message | rest] = messages
new_state = %{new_state | queued_messages: rest}
{:reply, {:ok, first_message}, new_state}
end
response ->
# Error
{:reply, response, state}
end
end
def handle_call({:write, data, timeout}, _from, state) do
bin_data = IO.iodata_to_binary(data)
{:ok, framed_data, new_framing_state} =
state.framing.add_framing(bin_data, state.framing_state)
response = call_port(state, :write, {framed_data, timeout}, port_timeout(timeout))
new_state = %{state | framing_state: new_framing_state}
{:reply, response, new_state}
end
def handle_call({:configure, opts}, _from, state) do
new_framing = Keyword.get(opts, :framing, nil)
new_rx_framing_timeout = Keyword.get(opts, :rx_framing_timeout, state.rx_framing_timeout)
is_active = Keyword.get(opts, :active, state.is_active)
id_mode = Keyword.get(opts, :id, state.id)
state =
change_framing(
%{state | rx_framing_timeout: new_rx_framing_timeout, is_active: is_active, id: id_mode},
new_framing
)
response = call_port(state, :configure, opts)
{:reply, response, state}
end
def handle_call(:drain, _from, state) do
response = call_port(state, :drain, nil)
{:reply, response, state}
end
def handle_call({:flush, direction}, _from, state) do
fstate = state.framing.flush(direction, state.framing_state)
new_state = %{state | framing_state: fstate}
response = call_port(new_state, :flush, direction)
{:reply, response, new_state}
end
def handle_call(:signals, _from, state) do
response = call_port(state, :signals, nil)
{:reply, response, state}
end
def handle_call({:set_dtr, value}, _from, state) do
response = call_port(state, :set_dtr, value)
{:reply, response, state}
end
def handle_call({:set_rts, value}, _from, state) do
response = call_port(state, :set_rts, value)
{:reply, response, state}
end
def handle_call({:set_break, value}, _from, state) do
response = call_port(state, :set_break, value)
{:reply, response, state}
end
def handle_call({:controlling_process, pid}, _from, state) do
new_state = %{state | controlling_process: pid}
{:reply, :ok, new_state}
end
def handle_info({_, {:data, <<?n, message::binary>>}}, state) do
msg = :erlang.binary_to_term(message)
handle_port(msg, state)
end
def handle_info(:rx_framing_timed_out, state) do
{:ok, messages, new_framing_state} = state.framing.frame_timeout(state.framing_state)
new_state =
notify_timedout_messages(
%{state | rx_framing_tref: nil, framing_state: new_framing_state},
messages
)
{:noreply, new_state}
end
defp notify_timedout_messages(%{is_active: true, controlling_process: dest} = state, messages)
when dest != nil do
Enum.each(messages, &report_message(state, &1))
state
end
defp notify_timedout_messages(%{is_active: false} = state, messages) do
# IO.puts("Queuing... #{inspect(messages)}")
new_queued_messages = state.queued_messages ++ messages
%{state | queued_messages: new_queued_messages}
end
defp notify_timedout_messages(state, _messages), do: state
defp change_framing(state, nil), do: state
defp change_framing(state, framing_mod) when is_atom(framing_mod) do
change_framing(state, {framing_mod, []})
end
defp change_framing(state, {framing_mod, framing_args}) do
{:ok, framing_state} = framing_mod.init(framing_args)
%{state | framing: framing_mod, framing_state: framing_state}
end
defp call_port(state, command, arguments, timeout \\ 4000) do
msg = {command, arguments}
send(state.port, {self(), {:command, :erlang.term_to_binary(msg)}})
# Block until the response comes back since the C side
# doesn't want to handle any queuing of requests. REVISIT
receive do
{_, {:data, <<?r, response::binary>>}} ->
:erlang.binary_to_term(response)
after
timeout ->
# Not sure how this can be recovered
exit(:port_timed_out)
end
end
defp handle_port({:notif, data}, state) when is_binary(data) do
# IO.puts "Received data on port #{state.name}"
{rc, messages, new_framing_state} = state.framing.remove_framing(data, state.framing_state)
new_state = handle_framing_timer(%{state | framing_state: new_framing_state}, rc)
if state.controlling_process do
Enum.each(messages, &report_message(new_state, &1))
end
{:noreply, new_state}
end
defp handle_port({:notif, data}, state) do
# Report an error from the port
if state.controlling_process do
report_message(state, data)
end
{:noreply, state}
end
defp report_message(state, message) do
event = {:circuits_uart, message_id(state.id, state.name), message}
send(state.controlling_process, event)
end
defp message_id(:pid, _name), do: self()
defp message_id(:name, name), do: name
defp genserver_timeout(timeout) when timeout >= 0 do
timeout + @genserver_timeout_slack
end
defp port_timeout(timeout) when timeout >= 0 do
timeout + @port_timeout_slack
end
# Stop the framing timer if active and a frame completed
defp handle_framing_timer(%{rx_framing_tref: tref} = state, :ok) when tref != nil do
_ = :timer.cancel(tref)
%{state | rx_framing_tref: tref}
end
# Start the framing timer if ended on an incomplete frame
defp handle_framing_timer(%{rx_framing_timeout: timeout} = state, :in_frame) when timeout > 0 do
_ = if state.rx_framing_tref, do: :timer.cancel(state.rx_framing_tref)
{:ok, tref} = :timer.send_after(timeout, :rx_framing_timed_out)
%{state | rx_framing_tref: tref}
end
# Don't do anything with the framing timer for all other reasons
defp handle_framing_timer(state, _rc), do: state
end
