Added ECHO cmd and fixed some timing issues

goTool/client_api.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"time"
 
 	"google.golang.org/protobuf/proto"
 
@@ -410,6 +411,66 @@ func (s *serialPort) espnowUnicastTest(clientID, seq uint32) (*pb.EspNowUnicastT
 	return r, nil
 }
 
+// EchoPingResult is the host-side round-trip for ESP-NOW echo ping.
+type EchoPingResult struct {
+	Success     bool    `json:"success"`
+	ClientID    uint32  `json:"client_id"`
+	TimestampUs uint64  `json:"timestamp_us"`
+	RttMs       float64 `json:"rtt_ms"`     // goTool: full UART round-trip
+	EspRttUs    uint32  `json:"esp_rtt_us"` // master: µs delta ping send → pong recv
+}
+
+func (s *serialPort) echoPing(clientID uint32) (*EchoPingResult, error) {
+	t0 := time.Now()
+	timestampUs := uint64(t0.UnixMicro())
+	req := &pb.EspNowEchoPingRequest{
+		ClientId:    clientID,
+		TimestampUs: timestampUs,
+	}
+	msg := &pb.UartMessage{
+		Type: pb.MessageType_ESPNOW_ECHO_PING,
+		Payload: &pb.UartMessage_EspnowEchoPingRequest{
+			EspnowEchoPingRequest: req,
+		},
+	}
+	body, err := proto.Marshal(msg)
+	if err != nil {
+		return nil, fmt.Errorf("encode: %w", err)
+	}
+	payload := append([]byte{byte(pb.MessageType_ESPNOW_ECHO_PING)}, body...)
+	respPayload, err := s.exchangePayload(payload, "ESPNOW_ECHO_PING")
+	if err != nil {
+		return nil, err
+	}
+	rttMs := float64(time.Since(t0).Microseconds()) / 1000.0
+
+	var respMsg pb.UartMessage
+	if err := proto.Unmarshal(respPayload[1:], &respMsg); err != nil {
+		return nil, fmt.Errorf("decode: %w", err)
+	}
+	r := respMsg.GetEspnowEchoPingResponse()
+	if r == nil {
+		return nil, fmt.Errorf("missing espnow_echo_ping_response")
+	}
+	if !r.GetSuccess() {
+		return &EchoPingResult{
+			Success:  false,
+			ClientID: r.GetClientId(),
+			RttMs:    rttMs,
+		}, nil
+	}
+	if r.GetTimestampUs() != timestampUs {
+		return nil, fmt.Errorf("timestamp mismatch: sent %d got %d", timestampUs, r.GetTimestampUs())
+	}
+	return &EchoPingResult{
+		Success:     true,
+		ClientID:    r.GetClientId(),
+		TimestampUs: r.GetTimestampUs(),
+		RttMs:       rttMs,
+		EspRttUs:    r.GetEspRttUs(),
+	}, nil
+}
+
 func (m *managedSerial) FindMe(clientID uint32) error {
 	return m.withPort(func(sp *serialPort) error {
 		return runFindMeClient(sp, clientID)
@@ -490,6 +551,20 @@ func (s *serialPort) EspnowUnicastTest(clientID, seq uint32) (*pb.EspNowUnicastT
 	return s.espnowUnicastTest(clientID, seq)
 }
 
+func (s *serialPort) EchoPing(clientID uint32) (*EchoPingResult, error) {
+	return s.echoPing(clientID)
+}
+
+func (m *managedSerial) EchoPing(clientID uint32) (*EchoPingResult, error) {
+	var result *EchoPingResult
+	err := m.withPort(func(sp *serialPort) error {
+		var e error
+		result, e = sp.echoPing(clientID)
+		return e
+	})
+	return result, err
+}
+
 func (s *serialPort) LedRing(req *pb.LedRingProgressRequest) (*pb.LedRingProgressResponse, error) {
 	return s.ledRingProgress(req)
 }