LoRa Protocol¶

The charger acts as a MQTT ↔ LoRa bridge. It translates all MQTT JSON commands into binary LoRa packets and vice versa.

Hardware¶

Property	Value
Module	EBYTE E32/E22 series
Frequency	433 MHz
UART	UART1 (TX=GPIO17, RX=GPIO18)
Mode pins	M0=GPIO12, M1=GPIO46

Operating Modes¶

M0	M1	Mode
0	0	Normal/transparent (data)
1	1	Configuration (AT-commands)

Packet Format¶

┌──────┬──────┬──────┬──────┬───────┬─────────────┬──────────┬──────┬──────┐
│ 0x02 │ 0x02 │ ADDR │ ADDR │ LEN+1 │ PAYLOAD...  │ XOR CSUM │ 0x03 │ 0x03 │
│ Start│ Start│ High │ Low  │       │             │          │ End  │ End  │
└──────┴──────┴──────┴──────┴───────┴─────────────┴──────────┴──────┴──────┘

Offset	Size	Value	Description
0-1	2	`0x02, 0x02`	Start bytes
2-3	2	Address	`0x00, 0x03` (TX to mower) / `0x00, 0x01` (RX from mower)
4	1	`len+1`	Payload length + 1
5..5+n	n	varies	Payload (command byte + data)
5+n	1	XOR	XOR checksum over all payload bytes
6+n, 7+n	2	`0x03, 0x03`	End bytes

Addresses¶

Address	Device
`0x00, 0x03`	Charger (sender)
`0x00, 0x01`	Mower (receiver)

Command Categories¶

The first byte of the payload identifies the command category:

Byte	Category	Description
`0x30` ('0')	CHARGER	Charger hardware (Hall sensor ACK, IRQ ACK)
`0x31` ('1')	RTK_RELAY	RTK GPS NMEA data relay to mower
`0x32` ('2')	CONFIG	Configuration commands
`0x33` ('3')	GPS	GPS position data (lat/lon/alt, 16 bytes)
`0x34` ('4')	REPORT	Status reports (heartbeat poll + mower data)
`0x35` ('5')	ORDER	Mowing commands (start/pause/stop/go_pile)
`0x36` ('6')	SCAN_CHANNEL	LoRa channel scan

See LoRa Packets for detailed packet structures. See LoRa Command Mapping for MQTT ↔ LoRa translation table.

Communication Flow¶

sequenceDiagram
    participant App
    participant Charger as Charger (MQTT + LoRa)
    participant Mower as Mower (LoRa)

    Note over Charger,Mower: Heartbeat (every ~1.5s)
    Charger->>Mower: LoRa [0x34, 0x01] (poll)
    Mower-->>Charger: LoRa [0x34, 0x02, status...] (19 bytes)
    Charger->>App: MQTT: up_status_info (includes mower data)

    Note over App,Mower: Command relay
    App->>Charger: MQTT: start_run
    Charger->>Charger: Translate to LoRa
    Charger->>Mower: LoRa [0x35, 0x01, mapName, area, height]
    Note over Charger: Wait max 3s for ACK
    Mower-->>Charger: LoRa ACK
    Charger->>App: MQTT: start_run_respond

    Note over Charger,Mower: RTK GPS relay
    Charger->>Charger: UM960 GNGGA NMEA
    Charger->>Mower: LoRa [0x31, NMEA_data...]
    Note over Mower: cm-accurate positioning

RSSI Measurement¶

Query:    [0xC0, 0xC1, 0xC2, 0xC3, 0x00, 0x01]
Response: [0xC1, 0x00, 0x01, <RSSI byte>]

RSSI < 146 (0x92) = good signal
Channel scan: tries all channels from lc to hc, sorts by RSSI (bubble sort), picks best