SENT (protocol)

SENT ( Single Edge Nibble Transmission ) is a digital interface for communication between sensors and control units in automotive electronics. It is described in SAE J2716.

Properties

There is a way, asynchronous voltage interface that requires three wires: power supply voltage (5V ) signal voltage (low- level < 0.5 V, high level> 4.1 V ) and ground. Data is transmitted in units of 4 bits = 1 nibble for which the time between two falling edges ( falling edge ) is evaluated with a constant amplitude of the modulated signal voltage. A data frame consists of 24 bits for data (each 3 nibbles for two measuring channels, eg for pressure and temperature), 4 bits = 1 nibble for error detection (CRC) and 4 bits = 1 nibble of status and communication, in total 8 nibbles. Alternatively, data can be transferred in a 5 - nibble - frame, with three nibbles for a single measurement channel and each one nibble for CRC and for status / communication.

In addition, 2 bits is defined from the nibble for " status and communication " another serial transport stream can be transmitted over the additional messages with correspondingly slower transfer rate ( "slow channel" ). Such a message is made up of an identifier (ID) and a value of a CRC checksum for the message; Catalog Sets the Sensor IDs is typically transmitted cyclically. The transmission is either 4-bit ID and 8-bit data into 16 consecutive data frames (short message format), or by 8-bit and 12-bit ID data into 18 consecutive data frames (Enhanced Message Format ).

Contents are static values ​​such as Identification of sensor type, manufacturer identification, sensor characteristic ( assignment of the measured value to physical sizes), but also variable values ​​such as Error code or temperature with lower requirements on the repetition rate. This means that an automatic detection of sensor types or a recognition of Falschverbau.