feat(inputs.modbus): Add RS485 specific config options (#12786)

plugins/inputs/modbus/README.md

@@ -41,6 +41,7 @@ See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
   controller = "tcp://localhost:502"
 
   ## Serial (RS485; RS232)
+  ## For RS485 specific setting check the end of the configuration.
   ## For unix-like operating systems use:
   # controller = "file:///dev/ttyUSB0"
   ## For Windows operating systems use:
@@ -235,6 +236,21 @@ See the [CONFIGURATION.md][CONFIGURATION.md] for more details.
       machine = "impresser"
       location = "main building"
 
+  ## RS485 specific settings. Only take effect for serial controllers.
+  ## Note: This has to be at the end of the modbus configuration due to
+  ## TOML constraints.
+  # [inputs.modbus.rs485]
+    ## Delay RTS prior to sending
+    # delay_rts_before_send = "0ms"
+    ## Delay RTS after to sending
+    # delay_rts_after_send = "0ms"
+    ## Pull RTS line to high during sending
+    # rts_high_during_send = false
+    ## Pull RTS line to high after sending
+    # rts_high_after_send = false
+    ## Enabling receiving (Rx) during transmission (Tx)
+    # rx_during_tx = false
+
   ## Enable workarounds required by some devices to work correctly
   # [inputs.modbus.workarounds]
     ## Pause after connect delays the first request by the specified time.

plugins/inputs/modbus/modbus.go

@@ -33,23 +33,34 @@ type ModbusWorkarounds struct {
 	ReadCoilsStartingAtZero bool            `toml:"read_coils_starting_at_zero"`
 }
 
+// According to github.com/grid-x/serial
+type RS485Config struct {
+	DelayRtsBeforeSend config.Duration `toml:"delay_rts_before_send"`
+	DelayRtsAfterSend  config.Duration `toml:"delay_rts_after_send"`
+	RtsHighDuringSend  bool            `toml:"rts_high_during_send"`
+	RtsHighAfterSend   bool            `toml:"rts_high_after_send"`
+	RxDuringTx         bool            `toml:"rx_during_tx"`
+}
+
 // Modbus holds all data relevant to the plugin
 type Modbus struct {
-	Name             string            `toml:"name"`
+	Name              string            `toml:"name"`
-	Controller       string            `toml:"controller"`
+	Controller        string            `toml:"controller"`
-	TransmissionMode string            `toml:"transmission_mode"`
+	TransmissionMode  string            `toml:"transmission_mode"`
-	BaudRate         int               `toml:"baud_rate"`
+	BaudRate          int               `toml:"baud_rate"`
-	DataBits         int               `toml:"data_bits"`
+	DataBits          int               `toml:"data_bits"`
-	Parity           string            `toml:"parity"`
+	Parity            string            `toml:"parity"`
-	StopBits         int               `toml:"stop_bits"`
+	StopBits          int               `toml:"stop_bits"`
-	Timeout          config.Duration   `toml:"timeout"`
+	RS485             *RS485Config      `toml:"rs485"`
-	Retries          int               `toml:"busy_retries"`
+	Timeout           config.Duration   `toml:"timeout"`
-	RetriesWaitTime  config.Duration   `toml:"busy_retries_wait"`
+	Retries           int               `toml:"busy_retries"`
-	DebugConnection  bool              `toml:"debug_connection"`
+	RetriesWaitTime   config.Duration   `toml:"busy_retries_wait"`
-	Workarounds      ModbusWorkarounds `toml:"workarounds"`
+	DebugConnection   bool              `toml:"debug_connection"`
-	Log              telegraf.Logger   `toml:"-"`
+	Workarounds       ModbusWorkarounds `toml:"workarounds"`
-	// Register configuration
+	ConfigurationType string            `toml:"configuration_type"`
-	ConfigurationType string `toml:"configuration_type"`
+	Log               telegraf.Logger   `toml:"-"`
+
+	// Configuration type specific settings
 	ConfigurationOriginal
 	ConfigurationPerRequest
 
@@ -285,6 +296,14 @@ func (m *Modbus) initClient() error {
 			if m.DebugConnection {
 				handler.Logger = m
 			}
+			if m.RS485 != nil {
+				handler.RS485.Enabled = true
+				handler.RS485.DelayRtsBeforeSend = time.Duration(m.RS485.DelayRtsBeforeSend)
+				handler.RS485.DelayRtsAfterSend = time.Duration(m.RS485.DelayRtsAfterSend)
+				handler.RS485.RtsHighDuringSend = m.RS485.RtsHighDuringSend
+				handler.RS485.RtsHighAfterSend = m.RS485.RtsHighAfterSend
+				handler.RS485.RxDuringTx = m.RS485.RxDuringTx
+			}
 			m.handler = handler
 		case "ASCII":
 			handler := mb.NewASCIIClientHandler(path)
@@ -296,6 +315,14 @@ func (m *Modbus) initClient() error {
 			if m.DebugConnection {
 				handler.Logger = m
 			}
+			if m.RS485 != nil {
+				handler.RS485.Enabled = true
+				handler.RS485.DelayRtsBeforeSend = time.Duration(m.RS485.DelayRtsBeforeSend)
+				handler.RS485.DelayRtsAfterSend = time.Duration(m.RS485.DelayRtsAfterSend)
+				handler.RS485.RtsHighDuringSend = m.RS485.RtsHighDuringSend
+				handler.RS485.RtsHighAfterSend = m.RS485.RtsHighAfterSend
+				handler.RS485.RxDuringTx = m.RS485.RxDuringTx
+			}
 			m.handler = handler
 		default:
 			return fmt.Errorf("invalid transmission mode %q for %q", m.TransmissionMode, u.Scheme)

plugins/inputs/modbus/sample_general_begin.conf

@@ -24,6 +24,7 @@
   controller = "tcp://localhost:502"
 
   ## Serial (RS485; RS232)
+  ## For RS485 specific setting check the end of the configuration.
   ## For unix-like operating systems use:
   # controller = "file:///dev/ttyUSB0"
   ## For Windows operating systems use:

plugins/inputs/modbus/sample_general_end.conf

@@ -1,3 +1,18 @@
+  ## RS485 specific settings. Only take effect for serial controllers.
+  ## Note: This has to be at the end of the modbus configuration due to
+  ## TOML constraints.
+  # [inputs.modbus.rs485]
+    ## Delay RTS prior to sending
+    # delay_rts_before_send = "0ms"
+    ## Delay RTS after to sending
+    # delay_rts_after_send = "0ms"
+    ## Pull RTS line to high during sending
+    # rts_high_during_send = false
+    ## Pull RTS line to high after sending
+    # rts_high_after_send = false
+    ## Enabling receiving (Rx) during transmission (Tx)
+    # rx_during_tx = false
+
   ## Enable workarounds required by some devices to work correctly
   # [inputs.modbus.workarounds]
     ## Pause after connect delays the first request by the specified time.