Elm Electronics – Circuits for the Hobbyist
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ELM327DSH
Electrical Information Pin Descriptions........................................................................... 3
Unused Pins.................................................................................5
Ordering Information.................................................................... 5
Absolute Maximum Ratings......................................................... 5
Electrical Characteristics..............................................................6
Using the ELM327 Overview...................................................................................... 7
Communicating with the ELM327................................................ 7
AT Commands............................................................................. 9
AT Command Summary...............................................................9
AT Command Descriptions........................................................ 11
Reading the Battery Voltage...................................................... 27
OBD Commands........................................................................28
Talking to the Vehicle.................................................................29
Interpreting Trouble Codes........................................................ 31
Resetting Trouble Codes........................................................... 32
Quick Guide for Reading Trouble Codes................................... 32
Bus Initiation...............................................................................33
Wakeup Messages.....................................................................33
Selecting Protocols.................................................................... 34
OBD Message Formats..............................................................35
Setting the Headers................................................................... 37
Monitoring the Bus..................................................................... 40
CAN Messages and Filtering..................................................... 41
Multiline Responses...................................................................42
CAN Message Formats..............................................................44
Restoring Order..........................................................................45
Advanced Features Altering Flow Control Messages................................................ 46
Using CAN Extended Addresses............................................... 47
SAE J1939 Messages................................................................48
Using J1939............................................................................... 50
The FMS Standard.....................................................................53
Programmable Parameters........................................................54
Programmable Parameter Summary......................................... 55
Using Higher RS232 Baud Rates...............................................59
Setting Timeouts - AT ST and AT AT Commands..................... 61
Power Control............................................................................ 62
Design Examples Microprocessor Interfaces..........................................................64
Example Applications.................................................................65
Modifications for Low Power Standby Operation....................... 70
Misc. Error Messages and Alerts.........................................................72
Outline Diagrams....................................................................... 74
Copyright and Disclaimer...........................................................74
Index.......................................................................................... 75
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