Hongyuv ultrasonic anemometer + RPI RS486 HAT

main.go

package main

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"time"
)
import "github.com/goburrow/modbus"

func main() {
	fmt.Println("Starting...")

	handler := modbus.NewRTUClientHandler("/dev/ttyAMA0")

	handler.BaudRate = 9600
	handler.DataBits = 8
	handler.Parity = "E"
	handler.StopBits = 1

	handler.SlaveId = 1
	handler.Timeout = 5 * time.Second
	//    handler.Logger = log.New(os.Stdout, "mb: ", log.Lshortfile)

	if err := handler.Connect(); err != nil {
		panic("RS485 error conecting: " + err.Error())
	}

	fmt.Println("RS485 initialized...")
	//...

	for true {
		client := modbus.NewClient(handler)
		results, err := client.ReadHoldingRegisters(0, 41)
		if err != nil {
			panic("RS485 error reading modbus: " + err.Error())
		}

		var response struct {
			Id        uint16
			Direction uint16

			Speed float32
		}

		// some weird chinese float encoding flipping, we are fixing that
		l1 := results[6]
		l2 := results[7]
		results[6] = results[4]
		results[7] = results[5]
		results[4] = l1
		results[5] = l2
		// end of weird chinese trickery

		reader := bytes.NewReader(results)
		if err := binary.Read(reader, binary.BigEndian, &response); err != nil {
			panic("binary.Read failed:" + err.Error())
		}

		//    fmt.Print("ID: ")
		//    fmt.Println(response.Id)
		fmt.Print(time.Now().Format(time.RFC3339))
		fmt.Print(" direction: ")
		fmt.Print(response.Direction)
		fmt.Print(", speed: ")
		fmt.Println(response.Speed)

		time.Sleep(time.Second)
	}
}