doc: Add OpenAPI specification for modbus node-type

Signed-off-by: Philipp Jungkamp <Philipp.Jungkamp@opal-rt.com>

doc/openapi/components/schemas/config/node_obj.yaml

@@ -34,6 +34,7 @@ discriminator:
     influxdb: nodes/_influxdb.yaml
     kafka: nodes/_kafka.yaml
     loopback: nodes/_loopback.yaml
+    modbus: nodes/_modbus.yaml
     mqtt: nodes/_mqtt.yaml
     nanomsg: nodes/_nanomsg.yaml
     ngsi: nodes/_ngsi.yaml

doc/openapi/components/schemas/config/nodes/_modbus.yaml

@@ -0,0 +1,3 @@
+allOf:
+- $ref: ../node_obj.yaml
+- $ref: modbus.yaml

doc/openapi/components/schemas/config/nodes/modbus.yaml

@@ -0,0 +1,108 @@
+# yaml-language-server: $schema=http://json-schema.org/draft-07/schema
+---
+
+allOf:
+- type: object
+  anyOf:
+  - required: [transport, remote]
+    properties:
+
+      transport:
+        type: string
+        enum:
+        - tcp
+
+      remote:
+        type: string
+        description: The hostname or IP of the modbus TCP device.
+        example: example.com
+
+      port:
+        type: integer
+        description: The port number of the modbus TCP device.
+        default: 1883
+
+      unit:
+        type: integer
+        description: The addressed unit used for serial communication. This is optional for TCP.
+        minimum: 0
+        maximum: 65535
+        example: 1
+
+  - required: [transport, device, baudrate, parity, data_bits, stop_bits, unit]
+    properties:
+
+      transport:
+        type: string
+        enum:
+        - rtu
+
+      device:
+        type: string
+        description: Path to the serial device file.
+        example: /dev/ttyS0
+
+      baudrate:
+        type: integer
+        description: The baudrate used for serial communication.
+        example: 9600
+
+      parity:
+        type: string
+        enum:
+        - none
+        - even
+        - odd
+        description: The parity used for serial communication.
+        example: none
+
+      data_bits:
+        type: integer
+        description: The data bits used for serial communication.
+        minimum: 5
+        maximum: 8
+        example: 5
+
+      stop_bits:
+        type: integer
+        description: The stop bits used for serial communication.
+        minimum: 1
+        maximum: 2
+        example: 5
+
+      unit:
+        type: integer
+        description: The addressed unit used for serial communication. This is optional for TCP.
+        minimum: 0
+        maximum: 65535
+        example: 1
+
+  properties:
+
+    response_timeout:
+      type: number
+      description: The timeout in seconds when waiting for responses from a modbus server.
+      example: 1.0
+
+    rate:
+      type: number
+      description: The rate at which modbus device registers are queried for changes.
+      example: 1.0
+
+    in:
+      type: object
+      properties:
+        signals:
+          type: array
+          items:
+            $ref: ./signals/modbus_signal.yaml
+
+    out:
+      type: object
+      properties:
+        signals:
+          type: array
+          items:
+            $ref: ./signals/modbus_signal.yaml
+
+- $ref: ../node.yaml

doc/openapi/components/schemas/config/nodes/signals/modbus_signal.yaml

@@ -0,0 +1,45 @@
+# yaml-language-server: $schema=http://json-schema.org/draft-07/schema
+---
+
+allOf:
+- type: object
+  required: [type, address]
+  properties:
+
+    address:
+      type: integer
+      description: The modbus register address.
+
+    word_endianess:
+      type: string
+      enum:
+      - big
+      - little
+      description: The ordering of two modbus registers joined together to form a larger number.
+      default: "big"
+
+    byte_endianess:
+      type: string
+      enum:
+      - big
+      - little
+      description: The ordering of the bytes within a modbus register.
+      default: "big"
+
+    scale:
+      type: number
+      description: The scale of the register's value.
+      default: 1.0
+
+    offset:
+      type: number
+      description: The offset of the register's value.
+      default: 0.0
+
+    bit:
+      type: integer
+      description: The bit index within a register.
+      minimum: 0
+      maximum: 15
+
+- $ref: ../../signal.yaml