SENT Encoder Example

Table of Contents

• Introduction
• SENT Signal
• Supported Combinations
• Steps to Run the Example
  • Sample Output
• Steps to modify SENT encoder example

Introduction

This example emulates SENT sensor using PRU ICSS.

**The SENT encoder Example is a reference for software based implementation of sent sensor. It is meant for only validating SENT Decoder Example .**

SENT Signal

The sensor sends out a signal that is made up of a string of pulses with data encoded as falling to falling edge periods. It happens independently of any receiver module activity and takes place without the receiver module sending a synchronization signal. The modulated signal with a constant amplitude voltage and an evaluation of the time interval between two falling edges (a single edge) is delivered in units of 4 bits (1 nibble), which can represent values ranging from 0 to 15. According to the SAE J2716 specification, a transmitter-specific nominal clock period that is used to quantify the pulse period (tick time) can be between 3-90 ms. The sensor device can use low-cost RC oscillators because the maximum permitted clock deviation is 20% from the normal tick time. The specified tick time, the sent data value, and the message time of a SENT message determine its duration. The following pulses (all with nominal timings) make up the transmitting sequence:

1. Synchronization/calibration pulse, first (56 clock ticks)
2. A single pulse with a 4 bit Status and Serial Communication header (12 to 27 clock ticks)
3. A series of one to six data nibble pulses, each reflecting the values of the signal(s) to be conveyed and lasting 12 to 27 clock ticks. Since the trailing falling edge of the SENT transmission CRC nibble also serves as the leading falling edge of the subsequent SENT transmission synchronization/calibration pulse, the number of nibbles will be fixed for each application of the encoding scheme (such as throttle position sensors, mass air flow, etc.).
4. One 4-bit checksum(CRC) nibble pulse (12 to 27 clock ticks)
5. One optional pause pulse

SENT Signal

Supported Combinations

Parameter	Value
ICSSM	ICSSM - PRU0
Toolchain	pru-cgt
Board	am263x-cc
Example folder	examples/pru_io/sent/encoder/encoder_example

Steps to Run the Example

• When using CCS projects to build, Import sent_encoder_r5f project from the above mentioned Example folder path.
• Build the project.
• Load R5F project, run it.

Note

Prerequisite: PRU-CGT-2-3 (ti-pru-cgt) should be installed at: C:/ti/

Launch a CCS debug session and run the executable, see CCS Launch, Load and Run Open a UART terminal and use config menu to send SENT frames Setup UART Terminal

Sample Output

******************SENT ENCODER Application**********************
 
SENT PRU-ICSS firmware loaded and running
 
 
 
Test with one sent frame: Y or N
y
 
SENT Frame...transmitted
 
Number of Frames transmitted:    1
Test with one sent frame: Y or N
n
 
Exiting Application

Note

• See list supported firmware design and list of supported feature : SENT

Steps to modify SENT encoder example

Modification supported: Change hardcoded tick period in fw. Current release supports only 500ns tick period support in firmware. In order to modify it:

• When using CCS projects to build, Import encoder_pru_fw project from the above mentioned Example folder path.
• In main.asm file modify TICK_PRD_100ns to desired value divided by 100. For example for 3000ns.

  TICK_PRD_100ns .set  30 ;Hard coding Tick period for now

• Rebuild examples\pru_io\sent\encoder\encoder_pru1_fw project
• Rebuild examples\pru_io\sent\encoder\encoder_example
• Load R5F updated binary, run it.