Add set_servo_angle to Firmware Behaviour.

lib/farmbot/firmware/handler.ex

@@ -77,4 +77,7 @@ defmodule Farmbot.Firmware.Handler do
   @doc "Request firmware version."
   @callback request_software_version(handler) :: fw_ret_val
 
+  @doc "Set angle on a servo pin."
+  @callback set_servo_angle(handler, pin, number) :: fw_ret_val
+
 end

lib/farmbot/firmware/stub_handler.ex

@@ -70,6 +70,10 @@ defmodule Farmbot.Firmware.StubHandler do
     GenStage.call(handler, :request_software_version)
   end
 
+  def set_servo_angle(handler, pin, number) do
+    GenStage.call(handler, {:set_servo_angle, pin, number})
+  end
+
   ## GenStage Behaviour
 
   defmodule State do
@@ -164,4 +168,8 @@ defmodule Farmbot.Firmware.StubHandler do
   def handle_call(:request_software_version, _, state) do
     {:reply, :ok, [{:report_software_version, "STUBFW"}, :done], state}
   end
+
+  def handle_call({:set_servo_angle, pin, angle}, _, state) do
+    {:reply, :ok, [], state}
+  end
 end

lib/farmbot/firmware/uart_handler/uart_handler.ex

@@ -68,6 +68,10 @@ defmodule Farmbot.Firmware.UartHandler do
     GenStage.call(handler, :request_software_version)
   end
 
+  def set_servo_angle(handler, pin, number) do
+    GenStage.call(handler, {:set_servo_angle, pin, number})
+  end
+
   ## Private
 
   defmodule State do
@@ -287,6 +291,10 @@ defmodule Farmbot.Firmware.UartHandler do
     do_write("F83", state)
   end
 
+  def handle_call({:set_servo_angle, pin, angle}, _, state) do
+    do_write("F61 P#{pin} V#{angle}", state)
+  end
+
   def handle_call(_call, _from, state) do
     {:reply, {:error, :bad_call}, [], state}
   end