OTA (Over-The-Air) Packet: Difference between revisions

Revision as of 09:20, 21 July 2025

Field	Size (bits)	Bit Range	Description	Breakdown
Header
Start byte	8	0–7	Starting character $ (ASCII value 36)	$
Data length	12	8–18	2-byte length of the data following the header	—
Num of data packets	5	19–23	Number of packets (0–32)	0 - 32
IMEI	50	24–74	Unique device identifier	Integer type: e.g., 887744556677882
Packet Type	5	75–79	Type of packet	00 - Device info 01 - Alert packet 02 - OTA pkt 03 - Error Packet 04 - Device configuration packet 05 - IP configuration packet
Data
OTA Source	5	—	Source of OTA	00 - OTA_SRC_SERIAL 01 - OTA_SRC_SMS 02 - OTA_SRC_IP_TRANSIGHT 03 - OTA_SRC_IP_CUSTOMER
Error status	8	—	Non-zero value indicates an error	0 = No Error, Non-zero = Error
Cell Number	51	—	First bit (MSB) indicates presence of country code. Remaining 50 bits = mobile number	Example: 400D6276ACF52 (+919784312658)
Date & Time	32	—	UTC Timestamp	UTC time in seconds
Timezone	8	—	Timezone in quarter-hours (e.g., 22 = +5:30)	22 × 15 mins = 330 mins = +5:30
Command Length	8	—	Length of command string	—
Command	up to 600 bits (75 bytes)	—	Command with arguments, null-terminated string	Example: SET CUIOCFG:IO1-DI-IGNIO2_AN_GENIO3-DI-PBNIO4-DO-IMB
Response Length	8	—	Length of response string	—
Response	up to 512 bits (64 bytes)	—	Response string from device	Example: IOCFG:IO1-DI-IGNIO2-AN_GENIO3-DI-PBNIO4-DO-IMB
Tail
End Character	8	0–7	End character * (ASCII value 42)	*
CRC	8	8–15	8-bit XOR CRC from $ to * (excluding both)	—

Sample Packet

 {"HEX:240340e1cabd09208ca210000000000000006824646f160947455420545355524c1c55524c3a5443503a3134312e3134372e3132382e3135303a383738382aa2",
  "cell_no": 0,
  "command": "GET TSURL",
  "command_length": 9,
  "dateTime": 1747215471,
  "dateTime_tz": "2025-05-14 15:07:51.000",
  "error_status": 0,
  "imei": 860187062240357,
  "insert_time": "Wed, 14 May 2025 09:38:03 GMT",
  "ota_source": 2,
  "packetType": 2,
  "response": "URL:TCP:141.147.128.150:8788",
  "response_length": 28,
  "send_time": "2025-05-14 15:07:51",
  "timezone": 22}

 <meta charset="UTF-8">
 <title>OTA Packet Parser</title>
 <style>
   body { font-family: Arial, sans-serif; padding: 20px; }
   textarea { width: 100%; height: 100px; font-family: monospace; margin-bottom: 10px; }
   button {
     padding: 10px 20px; border-radius: 20px;
     font-weight: bold; background-color: #680022; color: white;
     border: none; cursor: pointer;
   }
   button:hover { background-color: #680022; }
   table { width: 100%; border-collapse: collapse; margin-top: 20px; }
   th, td { border: 1px solid #ccc; padding: 8px; }
   th { background-color: #680022; color: white; }
 </style>

</head> <body>

OTA Packet Parser

<textarea id="hexInput" placeholder="Paste OTA packet hex here..."></textarea>
<button onclick="parseOTAPacket()">Parse OTA Packet</button>

Parsed Output:

 <tbody></tbody>

Field	Value

 return hex.match(/.{1,2}/g).map(b =>
   parseInt(b, 16).toString(2).padStart(8, '0')).join();

}

function bitsToInt(bits) {

 return parseInt(bits, 2);

}

function bitsToSignedInt(bits) {

 let value = parseInt(bits, 2);
 const max = Math.pow(2, bits.length);
 return value >= max / 2 ? value - max : value;

}

function bigIntFromBits(bits) {

 return BigInt('0b' + bits).toString();

}

function bitsToAscii(bits) {

 let ascii = ;
 for (let i = 0; i < bits.length; i += 8) {
   const byte = bits.slice(i, i + 8);
   ascii += String.fromCharCode(parseInt(byte, 2));
 }
 return ascii;

}

function parseOTAPacket() {

 const hex = document.getElementById("hexInput").value.trim().toLowerCase();
 const resultBody = document.querySelector("#resultTable tbody");
 resultBody.innerHTML = "";

 if (!hex.startsWith("24")) {
   alert("Packet must start with hex '24'");
   return;
 }

 const bits = hexToBits(hex);
 const getBits = (start, end) => bits.slice(start, end);
 const output = (label, value) => {
   const row = document.createElement("tr");

row.innerHTML = `${label}${value}`;

   resultBody.appendChild(row);
 };

 // Parse known fixed fields
 const imei = bigIntFromBits(getBits(25, 75));  // Correct IMEI parse
 output("IMEI", imei);

 output("Packet Type", bitsToInt(getBits(75, 80)));
 output("OTA Source", bitsToInt(getBits(80, 85)));
 output("Error Status", bitsToInt(getBits(85, 93)));

 const cellBits = getBits(93, 144);
 const isWithCountryCode = cellBits[0] === '1';
 const cellNo = parseInt(cellBits.slice(1), 2);
 output("Cell Number", isWithCountryCode ? `+${cellNo}` : cellNo);

 const dt = bitsToInt(getBits(144, 176));
 output("UTC Timestamp", new Date(dt * 1000).toISOString());

 const timezoneRaw = bitsToSignedInt(getBits(176, 184));
 const offsetMinutes = timezoneRaw * 15;
 const h = Math.floor(Math.abs(offsetMinutes) / 60);
 const m = Math.abs(offsetMinutes % 60);
 const tzSign = offsetMinutes >= 0 ? "+" : "-";
 output("Timezone", `${offsetMinutes} mins = UTC${tzSign}${h}:${m.toString().padStart(2, '0')}`);

 const localTime = new Date((dt + offsetMinutes * 60) * 1000)
   .toISOString().replace("T", " ").replace(".000Z", "");
 output("DateTime (Local)", localTime);

 const cmdLength = bitsToInt(getBits(184, 192));
 output("Command Length", cmdLength);

 const cmdBits = getBits(192, 192 + cmdLength * 8);
 const command = bitsToAscii(cmdBits);
 output("Command", command);

 const respLenStart = 192 + cmdLength * 8;
 const responseLength = bitsToInt(getBits(respLenStart, respLenStart + 8));
 output("Response Length", responseLength);

 const respBits = getBits(respLenStart + 8, respLenStart + 8 + responseLength * 8);
 const response = bitsToAscii(respBits);
 output("Response", response);

} </script>