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CAN Bus

The Controller Area Network (CAN) bus is a high-integrity serial communication protocol designed for real-time data exchange in embedded systems, particularly in automotive and industrial applications. It operates on a multi-master, message-oriented architecture, allowing multiple devices (nodes) to communicate on the same network without a central controller.

Interact

pip install python-can
pip install python-can-utils

import can
bus = can.Bus()
while True:
    msg = can.Message(3, data=[0 for _ in range(8)])
    bus.send(msg)

UDS

Unified Diagnostic Services (UDS) is a communication protocol used in automotive Electronic Control Units (ECUs) to enable diagnostics, firmware updates, routine testing and more.

Implementation

UDS message structure

SID

UDS SID (Request) UDS SID (Response) UDS Service Details
0x10 0x50 Diagnostic session control Control which UDS services are available.
0x11 0x51 ECU Reset It resets the ECU (includes hard reset, key off and soft reset)
0x27 0x67 Security access It enables use of security critical services via authentication.
0x28 0x68 Communication control This field turns send/receive of messages ON or OFF in the ECU.
0x29 0x69 Aunthentication Enables more advanced authentication vs. 0x27 (PKI based exchange).
0x3E 0x7E Tester present Send a heartbeat message periodically to remain in existing session .
0x83 0xC3 Access timing parameters View/Modify timing parameters used in client/server communication.
0x84 0xC4 Secured Data Transmission Send encrypted data via ISO 15764 (extended data link security)
0x85 0xC5 Control DTC Settings Enable/Disable detection of errors (e.g. used during diagnostics)
0x86 0xC6 Response On Event Request that ECU processes a service request if an event happens
0x87 0xC7 Link Control Set the baud rate for diagnostic access
0x22 0x62 Read Data by Identifier Read data from targetted ECU - e.g. VIN, sensor data etc.
0x23 0x63 Read Data by Address Read data from physical memory (e.g. to understand software behaviour)
0x24 0x64 Read Scaling Data By Identifier Read information about how to scale data identifiers
0x2A 0x6A Read Data by Identifier Periodic Request ECU to broadcast sensor data at slow/medium/fast/stop rate
0x2C 0x6C Dynamically Define Data Identifier Define data parameter for use in 0x22 or 0x2A dynamically
0x2E 0x6E Write Data By Identifier Program specific variables determined by data parameters
0x3D 0x7D Write Memory By address Write information to the ECU's memory
0x14 0x54 Clear Diagnostic Information Delete stored DTCs
0x19 0x59 Read DTC Information Read stored DTCs as well as related information
0x2F 0x6F Input Output Control By Identifier Gain control over ECU analog/digital inputs/outputs
0x31 0x71 Routine Control Initiate/stop routines (e.g. self testing, erasing of flash memory)
0x34 0x74 Request Download Start request to add software/data to ECU (including location/size)
0x35 0x75 Request Upload Start request to read software/data from ECU (including location/size)
0x36 0x76 Transfer Data Perform actual transfer of data following use of 0x74/0x75
0x37 0x77 Request Transfer Exit Stop the transfer of data
0x38 0x78 Request File Transfer Perform a file download/upload to/from the ECU
0x7F Negative Response Send with a negative response code when a request can not be handled.

References