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
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
Start the server
Link to this section Types
opt()
opt() :: MCP300X.read_opt() | {:name, module() | atom()}
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 (defaultMCP300X.id/1
):name
- a name for the server to globally register it (defaults to no name)
t()
t() :: pid()
t() :: pid()
Link to this section Functions
child_spec(init_arg)
Returns a specification to start this module under a supervisor.
See Supervisor
.
init(list)
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 callingSupervisor.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
.
read_channel(server, channel_number)
read_channel(t(), MCP300X.channel_number()) ::
{:ok, non_neg_integer()} | {:error, term()}
read_channel(t(), MCP300X.channel_number()) :: {:ok, non_neg_integer()} | {:error, term()}
start_link(bus_name, driver, opts \\ [])
start_link(binary() | charlist(), MCP300X.ADC.Driver.t(), [opt()]) ::
{:ok, t()} | GenServer.on_start()
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.
stop(server)
stop(t()) :: :ok
stop(t()) :: :ok