Allow configuring modbus connection timeout (evcc-io#613)

Author: andig

meter/modbus.go

@@ -3,6 +3,7 @@ package meter
 import (
 	"errors"
 	"fmt"
+	"time"
 
 	"github.com/andig/evcc/api"
 	"github.com/andig/evcc/util"
@@ -34,6 +35,7 @@ func NewModbusFromConfig(other map[string]interface{}) (api.Meter, error) {
 		Model              string
 		modbus.Settings    `mapstructure:",squash"`
 		Power, Energy, SoC string
+		Timeout            time.Duration
 	}{
 		Power: "Power",
 	}
@@ -55,6 +57,11 @@ func NewModbusFromConfig(other map[string]interface{}) (api.Meter, error) {
 		return nil, err
 	}
 
+	// set non-default timeout
+	if cc.Timeout > 0 {
+		conn.Timeout(cc.Timeout)
+	}
+
 	conn.Logger(log.TRACE)
 
 	// prepare device