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May 17, 2024 04:03
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package main | |
import ( | |
"encoding/json" | |
"flag" | |
"path/filepath" | |
"time" | |
nats "github.com/nats-io/nats.go" | |
log "github.com/sirupsen/logrus" | |
"prostocklivestock.com.au/thetooth/tagreader/internal/tag" | |
"github.com/tarm/serial" | |
) | |
func main() { | |
var urls = flag.String("s", "nats://192.168.0.246:4222,nats://192.168.0.245:4222,nats://192.168.0.244:4222", "The nats server URLs (separated by comma)") | |
var subj = flag.String("subject", "v1.ring.reader", "Subject to publish tags to.") | |
var port = flag.String("port", "/dev/ttyUSB0", "The _SERIAL_ port to use.") | |
var tim1 = flag.Int("timeout", 1000, "Time in milliseconds before assuming reader has failed.") | |
var tim2 = flag.Int("holdoff", 30, "Number of timeouts before assuming failure is critical.") | |
flag.Parse() | |
log.SetFormatter(&log.JSONFormatter{}) | |
// Connect to NATs | |
nc, err := nats.Connect(*urls, nats.Name("reader-agent"), nats.DisconnectErrHandler(func(_ *nats.Conn, err error) { | |
log.Fatalf("Client disconnected: %v", err) | |
})) | |
if err != nil { | |
log.Fatalf("Can't connect: %v\n", err) | |
} | |
defer nc.Close() | |
// Connect to serial port | |
c := &serial.Config{Name: *port, Baud: 9600, Parity: serial.ParityNone, StopBits: 1} | |
s, err := serial.OpenPort(c) | |
if err != nil { | |
log.Fatal(err) | |
} | |
defer s.Close() | |
// Perform initial set-up of the reader. | |
initReader(s, time.Millisecond*time.Duration(*tim1)) | |
// Reset handler | |
if _, err := nc.Subscribe(*subj+".reset", func(msg *nats.Msg) { | |
log.Infof("Got reset, reconfiguring S251B at %s", *port) | |
if _, err := s.Write([]byte("L\n\r")); err != nil { | |
log.Error(err) | |
} | |
}); err != nil { | |
log.Error(err) | |
} | |
st := make(chan string) | |
go func() { | |
buf := make([]byte, 1) | |
for { | |
_, err := s.Read(buf) | |
if err != nil { | |
log.Fatal(err) | |
} | |
st <- string(buf) | |
} | |
}() | |
// Reader loop. Scan port at 1 byte per pass, when we identify 'L' | |
// character clear tag value and start appending. When encountering | |
// a carriage return '\r', check if the contents of tag constitutes | |
// a valid TIRIS Animal Format. | |
// See: http://www.ti.com/lit/ug/scbu028/scbu028.pdf | |
tagbuf := "" | |
timeout := time.NewTicker(time.Millisecond * time.Duration(*tim1)) | |
timeoutCount := 0 | |
for { | |
select { | |
case symbol := <-st: | |
switch symbol { | |
case "L": | |
tagbuf = "" | |
case "\r": | |
if len(tagbuf) < 27 || tagbuf[:2] != "LA" { | |
if len(tagbuf) > 27 && tagbuf[:1] == "L" && tagbuf[3:4] == "A" { | |
log.Debug("Special reader") | |
} else { | |
log.Debug("Invalid tag") | |
continue | |
} | |
} | |
// Comply with NLIS format | |
tagbuf = tagbuf[len(tagbuf)-16:] | |
log.Printf("Port: %s Tag: %s", *port, tagbuf) | |
pack := tag.Payload{Tag: tagbuf, ReaderName: filepath.Base(*port)} | |
b, err := json.Marshal(pack) | |
if err != nil { | |
log.Fatal(err) | |
return | |
} | |
if err := nc.Publish(*subj+".stream", b); err != nil { | |
log.Fatal(err) | |
return | |
} | |
} | |
// Append symbol | |
tagbuf = tagbuf + symbol | |
// Reset timeout on symbol | |
timeout.Stop() | |
timeout = time.NewTicker(time.Millisecond * time.Duration(*tim1)) | |
timeoutCount = 0 | |
case <-timeout.C: | |
log.Warnf("Timer expired after %d ms waiting for a symbol, reconfiguring S251B at %s", *tim1, *port) | |
initReader(s, time.Millisecond*time.Duration(*tim1)) | |
if timeoutCount >= *tim2 { | |
log.Fatalf("Timeout occured %d times in a row! Going down!!!", timeoutCount) | |
} | |
timeoutCount++ | |
} | |
} | |
} | |
func initReader(s *serial.Port, timeout time.Duration) { | |
t := time.NewTimer(timeout) | |
c := make(chan struct{}, 1) | |
go func() { | |
if _, err := s.Write([]byte("L\n\r")); err != nil { | |
log.Error(err) | |
} | |
c <- struct{}{} | |
}() | |
select { | |
case <-t.C: | |
log.Fatal("Writing to port timed out!") | |
case <-c: | |
return | |
} | |
} |
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