Update README.md

Added API description

README.md

@@ -268,6 +268,54 @@ Select “App” under Settings. Here you have the option to configure some fron
 
 5. Voltage to SoC: Conversion of voltage to state of charge (simple linear interpolation). The recommended voltage min (0%) is the shutdown voltage from the config.h of your sunray FW +0.5V. The recommended voltage max (100%) is the final charging voltage from the config.h of your sunray FW -0.5V. The SoC display has no controlling function and only serves as an overview on the home page.
 
+### Api
+To control CaSSAndRA without UI an API can be activated. To set it up, go to Settings, then select API, click on MQTT, enter your data, save, and restart the backend server.
+If everything is entered correctly, you should see the following messages:
+    status
+    robot
+    maps
+    tasks
+    mow parameters
+    map
+    coords (only on request)
+The commands are sent to the "api_cmd" topic:
+You can find available names in the "maps" and "tasks" topics.
+1. Switch map:
+```{"maps": {"command": "load", "value": ["map name"]}}```
+
+2. Select task:
+```{"tasks": {"command": "select", "value": ["task name"]}}```
+
+3. Mow (all):
+```{"robot":{"command": "mow", "value": ["all"]}}```
+
+Mow (task):
+```{"robot":{"command": "mow", "value": ["task"9}}```
+
+Mow (selection):
+```{"robot":{"command": "mow", "value": ["selection"]}}```
+
+4. Stop:
+```{"robot":{"command": "stop"}}```
+
+5. Dock:
+```{"robot":{"command": "dock"}}```
+
+6. Change mow parameters:
+```{"mow parameters":{"pattern": "squares", "width": "0.20", "angle": 160, "distancetoborder": 5, "mowarea": true, "mowborder": 3, "mowexclusion": false, "mowborderccw": true}}```
+
+7. Set selection:
+```{"map":{"command":"set selection", "value":{"x": [0, 1, 1], "y": [0, 1, 0]}}}```
+
+8. Robot move (command should be sent continuously approx. every 0.1s):
+```{"robot":{"command":"move", "value":[value for linear speed, value for angular speed]}}```
+
+9. Get coordinates of current map:
+```{"coords":{"command":"update", "value":["current map"]}}```
+
+after that CaSSAndRA will publish coordinates of current map in GeoJSON format (coords topic)
+
+
 ## Mapping
 A new map or existing map can be created/modified on the "Mapping" page.