Add grisp example

Author: fhunleth

.credo.exs

@@ -4,7 +4,7 @@
     %{
       name: "default",
       files: %{
-        included: ["lib/"],
+        included: ["lib/", "examples/"],
         excluded: ["lib/i2c/i2c_nif.ex"]
       },
       strict: true,

examples/backends/grisp.ex

@@ -0,0 +1,78 @@
+defmodule Circuits.I2C.GRiSP do
+  @moduledoc """
+  Circuits.I2C backend for GRiSP
+
+  This is completely untested.
+  """
+  @behaviour Circuits.I2C.Backend
+
+  alias Circuits.I2C.Backend
+  alias Circuits.I2C.Bus
+
+  defstruct [:ref]
+
+  @doc """
+  Return the I2C bus names on this system
+
+  No supported options
+  """
+  @impl Backend
+  def bus_names(_options) do
+    :grisp_i2c.buses() |> Map.keys() |> Enum.map(&Atom.to_string/1)
+  end
+
+  @doc """
+  Open an I2C bus
+  """
+  @impl Backend
+  def open(bus_name, _options) do
+    ref = :grisp_i2c.open(String.to_atom(bus_name))
+    {:ok, %__MODULE__{ref: ref}}
+  end
+
+  @doc """
+  Return information about this backend
+  """
+  @impl Backend
+  def info() do
+    %{backend: __MODULE__}
+  end
+
+  defimpl Bus do
+    @impl Bus
+    def read(%Circuits.I2C.GRiSP{ref: ref}, address, count, _options) do
+      with [result] <- :grisp_i2c.transfer(ref, [{:read, address, 0, count}]) do
+        {:ok, result}
+      end
+    end
+
+    @impl Bus
+    def write(%Circuits.I2C.GRiSP{ref: ref}, address, data, _options) do
+      with [:ok] <- :grisp_i2c.transfer(ref, [{:write, address, 0, data}]) do
+        :ok
+      end
+    end
+
+    @impl Bus
+    def write_read(
+          %Circuits.I2C.GRiSP{ref: ref},
+          address,
+          write_data,
+          read_count,
+          options
+        ) do
+      with [:ok, result] <-
+             :grisp_i2c.transfer(ref, [
+               {:write, address, 0, write_data},
+               {:read, address, 0, count}
+             ]) do
+        {:ok, result}
+      end
+    end
+
+    @impl Bus
+    def close(%Circuits.I2C.GRiSP{ref: ref}) do
+      :ok
+    end
+  end
+end

mix.exs

@@ -32,7 +32,7 @@ defmodule Circuits.I2C.MixProject do
     ]
   end
 
-  defp elixirc_paths(env) when env in [:test, :dev], do: ["lib", "examples"]
+  defp elixirc_paths(env) when env in [:test, :dev], do: ["lib", "examples/circuits_sim"]
   defp elixirc_paths(_env), do: ["lib"]
 
   def application do