SENT protocol support

The Pulsed Output Module supports the SAE J2716 Single Edge Nibble Transmission (SENT) protocol and can simulate SENT-compatible sensors used in automotive applications for measurement of temperature, pressure, throttle position, mass airflow, etc.

The SENT signal consists in a series of messages, each of them consisting in a given number of 4-bit 'nibbles'.

The SENT signals selection and configuration are performed from the CPU model and its interface. This information is used to build the POM pulse trains, which are then transferred to the FPGA module which manages the output signals of the POM card.

The reference model provides a set of SENT-specific sub-panels in the POM module LabView panels. Although any of the 24 POM channels (PO1_24) can output one of the 5 SENT signals defined in the reference model, throughput limits apply : at 2ms model loop time, a maximum of 6 independent SENT transmitters can be simulated at the maximum data rate (24 bit values with a unit of time of 3 microseconds).

The following control and configuration features are supported :

General features:

Compatibility with SAE J2716 protocol revision of January 2010.
Support of short and enhanced serial protocol as defined in chapter 5.2.4.2 and 5.2.4.3 of SAE J2716 Jan2010.
Enhanced transmission supports either 12 bits of data and 8 bits of ID, or 16 bits of data and 4 bits of ID.
CRC legacy implementation (as in revision Feb2008 and older) or recommended implementation (as in revision Jan2010) with 16 or 256 elements array CRC.
CRC table files are transferred to the real-time computer when the model is loaded.

Communication :

Support for SENT communication fundamental unit time (nominal transmitter clock period) in the range of 1 to 300 µs. The unit time can be set to a decimal value in order to adapt to the exact tick tolerance of the SENT receiver.
Control for Start/Stop of the transmission.
Support for continuous transmission or transmission of a given number of consecutive messages.
Support for LSB-first or MSB-first nibbles transfer.
Control of the low-driven tick number, i.e number of ticks maintained low between pulses.
Refresh of the sensor data at each model time step.

Message format

Each message consists in 1 to 6 data nibbles and 1 status nibble.
Data nibbles are converted from engineering value to raw value : double to signed/unsigned integer type (4 to 24 bits).
An optional pause pulse can be configured. The pulse has a constant frame length. This length can either be configured with a specified tick number (between 12 and 768 ticks) or it can be dynamically calculated to adjust to the desired message size.
An optional sync pulse with configurable length can be configured. The pulse's length is specified in ticks number (default 56). Decimal values are supported so the sync pulse can be adjusted to the exact sync pulse length in µs expected by the receiver.

For each of the 5 SENT signals, the reference model provides a configuration sub-panel for these parameters :

Error insertion

The following errors can be inserted in the SENT signals waveforms. The errors are defined for each SENT signal, and applied either continuously or for a specified duration (i.e a specified number of messages).

Dynamic change of the length of the synchronization/calibration pulse by changing the number of unit times (min. 5 ticks).
Suppression of the synchronization pulse.
Suppression of the status pulse.
Suppression of the pause pulse.
Addition/subtraction nibbles to/from the end of the messages. The user specifies the number of nibbles and the starting position of the added or substracted nibbles. If adding nibbles, the user also specifies the nibble values.
Corruption of nibbles by dynamically specifying the number of unit times for a data nibble (undersized nibble from 5 to 12 ticks, oversized nibble from 27 ticks).
Corruption of the low portion of the nibbles.
Corruption of the CRC.
Suppression of the CRC.

For each of the 5 SENT signals, the reference model provides two configuration sub-panel for the configuration and control of these errors: