add skippable

main.go

@@ -3,6 +3,7 @@
 package main
 
 import (
+	"errors"
 	"flag"
 	"fmt"
 	"log"
@@ -108,6 +109,10 @@ func readRegs(client modbus.Client, start, qty uint16) {
 		}
 		val, err := reg.read(data[(addr-start-1)*2:])
 		if err != nil {
+			if errors.Is(err, errSkippableRead) {
+				log.Printf("Couldn't parse input register data, skipping: %v", err)
+				continue
+			}
 			log.Fatalf("Couldn't parse input register data: %v", err)
 		}
 		//fmt.Printf("%s: %v %s\n", reg.name, val, reg.unit)

sungrow_map.go

@@ -1,5 +1,11 @@
 package main
 
+import (
+	"encoding/binary"
+	"errors"
+	"fmt"
+)
+
 type register struct {
 	name string
 	conv func([]byte) (float64, error)
@@ -40,5 +46,20 @@ var sungrowInputRegs = map[uint16]*register{
 
 	5113: {"daily_running_time", u16, 1, "m"},
 	5144: {"total_power_yield_2", u32, 0.1, "kWh"},
-	5148: {"frequency_2", u16, 0.01, "Hz"},
+	5148: {"frequency_2", frequency2, 0.01, "Hz"},
+}
+
+var errSkippableRead = errors.New("skip read")
+
+func frequency2(data []byte) (float64, error) {
+	n := binary.BigEndian.Uint16(data)
+	if n == 0xFFFF {
+		// probably a misread
+		return 0, fmt.Errorf("likely misread: frequency_2 read %v", n)
+	}
+	if n == 100 {
+		// this translates as 1 Hz, which is unlikely
+		return 0, fmt.Errorf(" %w: frequency_2 is 1.00Hz", errSkippableRead)
+	}
+	return float64(n), nil
 }