Online PDU Encoder

Why use PDU mode instead of Text mode?

When sending SMS using a GSM modem or AT commands (such as AT+CMGS), PDU mode provides complete control over the message content, especially when dealing with Unicode/Chinese messages, long messages (concatenated messages), and status reports. While Text mode is simpler, it often results in garbled text when handling non-ASCII characters. Our online PDU encoding and decoding tool supports GSM 7-bit, 8-bit, and UCS2 encoding, helping developers quickly debug hardware.

Encode PDU by https://www.smsdeliverer.com

 
Text message:
SMSC:
Destination Number:
Encoding:
Validity period (hours):
Message refrence No.:
Source port:
Destination port:
Message class:
Status report:
Flash message:
 
PDU Code:

Detailed SMS-SUBMIT PDU Structure

The SMS-SUBMIT (Mobile Originated) PDU structure consists of the Service Center Address (SCA) and the Protocol Data Unit (PDU) itself. Below is the precise breakdown of each field.

Field Name Size Technical Detail & Encoding
SCA Length 1 Octet SMSC Address Length: Indicates the total length of the SMSC info (Type + Number).
SCA Type & Number Variable The phone number of the Service Center. Encoded as Address-Type (e.g., 91 for international) followed by the BCD-encoded number.
First Octet 1 Octet PDU Type: Defines parameters such as TP-MTI (Message Type Indicator), TP-RD (Reject Duplicates), and TP-VPF (Validity Period Format).
TP-MR 1 Octet Message Reference: A sequential reference number for the submitted message.
TP-DA Variable Destination Address: The recipient's number. Includes Digit Length, Type of Address, and BCD-encoded digits.
TP-PID 1 Octet Protocol Identifier: Identifies the higher layer protocol or interworking with specific networks (e.g., teletex, email).
TP-DCS 1 Octet Data Coding Scheme: Defines the alphabet and message class (GSM 7-bit, 8-bit Data, or UCS2/Unicode).
TP-VP Variable Validity Period: Specifies how long the message remains valid at the SMSC before being deleted.
TP-UDL 1 Octet User Data Length: Indicates the number of septets (for 7-bit) or octets (for 8/16-bit) in the message body.
TP-UD Variable User Data: The actual encoded message content (the payload).

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See also:
Online SMS PDU decoder