ardop: Add experimental FSKONLY mode

Set `ARDOP_FSKONLY_EXPERIMENT=1` to enable this.

Ref #84

transport/ardop/command.go

@@ -86,6 +86,7 @@ const (
 	cmdFECmode       command = "FECMODE"    // FECMODE<8FSK.200.25|4FSK.200.50S|4FSK.200.50,4PSK.200.100S|4PSK.200.100|8PSK.200.100|16FSK.500.25S|16FSK.500.25|4FSK.500.100S|4FSK.500.100| 4PSK.500.100|8PSK.500.100|4PSK.500.167|8PSK.500.167|4FSK.1000.100|4PSK.1000.100|8PSK.1000.100|4PSK.1000.167|8PSK.1000.167|4FSK.2000.600S|4FSK.2000.600|4FSK.2000.100|4PSK.2000.100|8PSK.2000.100|4PSK.2000.167|8PSK.2000.167
 	cmdFECrepeats    command = "FECREPEATS" // <0-5> Sets the number of times a frame is repeated in FEC (multicast) mode. Higher number of repeats increases good copy probability under marginal conditions but reduces net throughput.
 	cmdFECsend       command = "FECSEND"    // Start/Stop FEC broadcast/multicast mode for specific FECMODE. FECSEND <False> will abort a FEC broadcast.
+	cmdFSKOnly       command = "FSKONLY"    // <TRUE|FALSE> If true, only FSK modulation are used for ARQ connections (ARDOPc only?)
 
 )
 
@@ -128,7 +129,7 @@ func parseCtrlMsg(str string) ctrlMsg {
 
 	switch msg.cmd {
 	// bool
-	case cmdCodec, cmdPTT, cmdBusy, cmdTwoToneTest, cmdCWID, cmdListen, cmdAutoBreak:
+	case cmdCodec, cmdPTT, cmdBusy, cmdTwoToneTest, cmdCWID, cmdListen, cmdAutoBreak, cmdFSKOnly:
 		msg.value = strings.ToLower(parts[1]) == "true"
 
 	// Undocumented

transport/ardop/tnc.go

@@ -11,7 +11,9 @@ import (
 	"io"
 	"log"
 	"net"
+	"os"
 	"runtime"
+	"strconv"
 	"strings"
 	"time"
 
@@ -153,6 +155,13 @@ func (tnc *TNC) init() (err error) {
 		return fmt.Errorf("Disable listen failed: %s", err)
 	}
 
+	// FSKONLY experiment
+	if t, _ := strconv.ParseBool(os.Getenv("ARDOP_FSKONLY_EXPERIMENT")); t {
+		if err = tnc.setFSKOnly(true); err != nil {
+			return fmt.Errorf("Set FSK only failed: %s", err)
+		}
+		log.Println("Experimental FSKONLY mode enabled")
+	}
 	return nil
 }
 
@@ -536,6 +545,13 @@ func (tnc *TNC) SetListenEnabled(listen bool) error {
 	return tnc.set(cmdListen, fmt.Sprintf("%t", listen))
 }
 
+// Enable/disable the FSKONLY mode.
+//
+// When enabled, the TNC will only use FSK modulation for ARQ connections.
+func (tnc *TNC) setFSKOnly(t bool) error {
+	return tnc.set(cmdFSKOnly, fmt.Sprintf("%t", t))
+}
+
 // Disconnect gracefully disconnects the active connection or cancels an ongoing connect.
 //
 // The method will block until the TNC is disconnected.