mcp300x v0.1.0 MCP300X.Server

Use a MCP300X family ADC in a GenServer so it can be supervised.

This is useful for long running applications that will need to read from the ADC.

children = [
  {MCP300X.Server, ["spidev0.0", MCP300X.MCP3008, [name: MyApp.MCP3008]]}
]

opts = [strategy: :one_for_one, name: MyApp.Supervisor]
Supervisor.start_link(children, opts)

This you can use it so:

MCP300X.Server.read_channel(MyApp.MCP3008, 0)

Link to this section Summary

Types

Options for the MCP300X server

t()

Functions

Returns a specification to start this module under a supervisor

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

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opt()
opt() :: MCP300X.read_opt() | {:name, module() | atom()}

Options for the MCP300X server.

  • :convert_func - a conversion function to be used when readin the ADC value (default MCP300X.id/1)
  • :name - a name for the server to globally register it (defaults to no name)

Link to this section Functions

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child_spec(init_arg)

Returns a specification to start this module under a supervisor.

See Supervisor.

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 handle_info(:timeout, state) will be called after timeout milliseconds if no messages are received within the timeout.

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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read_channel(server, channel_number)
read_channel(t(), MCP300X.channel_number()) ::
  {:ok, non_neg_integer()} | {:error, term()}

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start_link(bus_name, driver, opts \\ [])
start_link(binary() | charlist(), MCP300X.ADC.Driver.t(), [opt()]) ::
  {:ok, t()} | GenServer.on_start()

Start the server.

Takes a SPI bus name, a Driver.t(), and opt.

If the SPI bus is invalid you will get {:error, :access_denied} when trying to start this process.

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stop(server)
stop(t()) :: :ok