Questions tagged [can]

CAN stands for Controller Area Network and is a bus often used in automotive applications. It is a two-wire differential protocol and works on baud rates from 10 kbits/sec to 1 Mbits/sec.

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42 views

CAN protocol CRC Generation and validation

AS per CAN communication protocol we have 15 bit of CRC field. Who is responsible for inserting the CRC field into CAN transmitting messages and validating the Receiving messages using checksum? ...
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39 views

Multiple CANOpen SDO requests "in the air" at once

In CANOpen, expedited SDO requests and responses include the index and sub-index of the request. All CANOpen master implementations that I've looked at require only one SDO per device be sent at once, ...
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Pullup resistor for automotive protocol like CAN and LIN

I understand that how open collector works on protocol like I2C. However, from my understanding, the automotive protocols like CAN and LIN also use open collector to talk to other devices. LIN is ...
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66 views

CAN bus - voltage drop with new component

I am trying to connect a new board to my CAN bus and I have an issue with the voltage. The new board is a Raspi 4 and has a "RS485 CAN HAT" connected to it. To debug, I use can-utils. When I ...
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41 views

Why does the CAN ID 7DF not work yet 7E0 does?

I am using https://github.com/Ircama/ELM327-emulator in order to simulate the can/elm327 response from a toyota euris hybrid. My understanding is that the header 7DF should be used when requesting ...
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52 views

Hardware based ECU flasher vs software

Why all of the automotive flash equipment require a hardware to write/read Flash memories? (Such as kess/bflash etc) It isn't possible with just a good quality OBD cable to connect to CAN BUS and read/...
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MCP2510 CAN controller: 16MHz Crystal not oscillating or oscillating at 150KHz

Issue: I have a board which uses a MCP2510 CAN controller and ATMega 32U4. During testing I found I couldn't communicate with the CAN controller. After some probing I found the CAN controller clock ...
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3answers
505 views

Stand alone CAN bus module or STM32 embedded CAN?

I have spent days studying and trying to achieve simple communications with CAN bus from scratch using stm32f1, but I still have not achieved the desired results and it is difficult to understand and ...
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71 views

Adding two termination resistors on the same node?

Can someone please explain to me why this is the wrong way to set up a CAN bus? When I measure the resistance between CANH and CANL I get 60Ω, so why must I put the termination resistor on node 2 when ...
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Alternatives to CAN for multi-master transmission

As usual these days I'm fighting against component shortage. As in completely redesigning boards since they give us lead times in the 2023 years. At the moment I have this product line where the ...
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118 views

Strange behavior of auto retransmission on STM32 CAN bus

I have two STM32L4Q5 controllers communicating over 500kBit/s CAN bus. The test application generates messages with variable length and data. The data checksum is used as low byte of message ID, while ...
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Transmit and receive in PDO for CANopen - Why use transmit channel?

According to CiA 301, there is something called TPDO Mapping and TPDO Communication. TPDO communication is used for describing ...
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Process Data Objects - CANopen - How do they work?

I'm searching for information about PDO and the protocol CiA 301 V4.2.0 at topic 7.2.2.5.1 does not exactly show how PDO's work. ...
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How do I find CAN bus?

I have 9 pins on power supply unit. Some of these pins are very likely CAN bus. What is a the best way to learn which pins are CAN bus? It is quit hard to disassemble that power supply unit to see ...
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When should I use normal SDO transfer in CANopen?

CANopen have two types of methods for transferring and receiving data between server and client. Expedited mode = Send fixed bytes (maximum 4 bytes) Normal mode = Send maximum 7 bytes at the time If ...
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1answer
70 views

Peer to Peer in CANopen - How does it work?

CANopen have something called an 11 bit COB-ID, it contains function code of 4 bits + node ID of 7 bits. For example: Image from here. Does this mean if the MASTER send a request to the CLIENT for ...
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Why are NMT masters acting as SDO clients and not SDO masters in CANopen?

According to CSSeletronics. What is the SDO service? The SDO service allows a CANopen node to read/edit values of another node's object dictionary over the CAN network. As mentioned under '...
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CAN-FD bit stuffing worst case standard identifier arbitration phase

This question arises from another one where the bit stuffing in data phase was under discussion. I replicate the computation performed in this document, but according to my computation the stuff bits ...
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60 views

CAN bus stub length calculation

I want to connect an MCP2562 to an ESP32 IC. I have desinged a PCB to accomdate these two ICs. The CAN bus runs at a 250 baud rate. I have done some research on how long the stubs must be between the ...
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What does Reset Node and Reset Communcation do in CANopen?

According to NI, NTM commands can be sent to the Node. They are the follwing: Start Remote Node Stop Remote Node Enter Pre-Operational Reset Node Reset Communication. Start Remote Node enables all ...
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Sending raw data with CANopen - Which function/COB should I use then?

I want to send raw data with CANopen. Which COB-ID should I use then? My goal is to transmit for example an array of X bytes and when the receiver got that array, it going to understand how to ...
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82 views

Why does SAE J1939 Commanded Address requires a delay when sending multiple package message?

I wonder why the command Commanded Address from SAE J1939-21 protocol, requries a delay between 50-200ms for every multiple package message for the transmitter. Why? Does the microcontroller unit not ...
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72 views

CAN bus terms relation

I'm trying to understand the relation among CAN clock frequency, Baud Rate Prescaler (BRP), Bus Baud rate and Bit Time. What is the relation between these 4 terms? How to get the Bus Baud Rate? I knew ...
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Modbus Vs CANopen - Which one should I choose?

Modbus Vs CANopen - Which one should I choose if I want: Broadcast to all units Talk to specific units Robust Send lots of data Implement for embedded systems Easy to use Using in new projects with ...
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Continuous polling, or continuous remote requests on a canbus

How can I establish continuous polling, or continuous remote requests on a canbus at a reasonable rate? Goal: A can node WSMSTR (Working Set Master) regularly acquires data from its can node WSMEMs (...
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Connecting CAN mcu [duplicate]

I have two TivaC M4C123G boards. Each board has MCU with two CANs. Within the same board if I connect the TX pin into RX pin would it work? Within the two boards if I connected the TX pin of MCU1 into ...
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Why common-mode choke on differential-signal serial lines?

I have 2 questions: Why using a common-mode choke on serial communication lines (like CAN, RS485) if the signal is differential? Wouldn't the common-mode noise simply be cancelled in the receiver? I ...
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66 views

Quick question regarding CANbus wiring

New to CANbus and just wondering about something. I want two nodes connected with CANbus. They have different MCU, transceivers and so on. Question is, can I just connect these on the same wire? (see ...
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Difference between Rs and INH Pin

I have this CANH CANL transceiver which I unfortunately cannot order anymore. I've found these two ICs: 1 2 The pins match with the original IC except for one pin. On the original IC it's called INH ...
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132 views

MCP2525 not initialized for CAN bus implementation

https://github.com/coryjfowler/MCP_CAN_lib/blob/master/examples/CAN_loopback/CAN_loopback.ino I'm using this library to implement CAN bus and I am using the loopback mode example using a single ...
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216 views

CAN bus voltage too low but resistance ok

I have a CAN device (PiCAN2 for Raspberry 2) that fails to send or receive CAN messages. The device itself is working, but no CAN messages are received or sent. Termination resistance is ok, so I ...
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48 views

Can0 return no data, but with no error

I'm actually trying to get data from a CAN on vehicle connected by DB9 on my raspberry. The DB9 provides also energy to the raspberry (here the material that i'm using). I've followed every of these ...
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Can a node on a terminated end of a CAN bus self-identify that it is the final node?

Using the example below, is there any way for Node1 or Node3 to be able to recognize that they are the final nodes on the CAN bus? I want to allow my device to automatically enable a 120Ohm ...
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CAN BUS circuit using arduino and STM32 not receiving data

I tried to connect arduino uno R3 to STM32 using MCP2515 CAN bus transceiver. This was the transmitter code: ...
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STM32 CAN not working - MIT Cheetah Controller

First of all, we produced two of the MIT-Motorcontrollers from this Repository: https://github.com/bgkatz/3phase_integrated with this Firmware: https://github.com/bgkatz/motorcontrol The controllers ...
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CAN connect two galvanic isolated systems

I have two sytems, one is a master system and the other is a slave system. Both systems are galvanic isolated and share no common potential. The two systems need to communicate over CAN (around 1m ...
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69 views

Help to identify CAN packets of a lift-fork

I have monitored the CAN bus of a lift-fork but I can't recognize the meaning of the packets that was being sent periodically on the bus. Do somebody have an idea on how to interpret these packets ...
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Wiggling connector receptacle housing causes CAN signal dropout?

I am currently using a 4pin molex Microlock 1.25mm connector that has a CAN connection as well as a power connection. pin 1 = power pin 2 = ground pin 3 = CAN_H pin 4 = CAN_L We recently discovered an ...
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MCP2515 CAN controller is not transmitting CAN frames , when loading CAN data through SPI interface at less than 8MHz frequency SCLK

MCP2515 CAN controller is not transmitting CAN frames , when loading CAN data through SPI interface at less than 8MHz frequency SCLK i am using MCP2515 CAN controller+ mcp2551 transceiver ...
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104 views

Sniffing a CAN Bus with strange behavior

I want to sniff data from a CAN Bus where are nodes using these parts: 1 - 18F24K20 - Microcontroller 2 - VP233 - CAN Transceiver 3 - 78L33A - Voltage Regulator These nodes are sensors that detect ...
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Role of CAN bus protection circuitry

Here is CAN protection circuitry as suggested by MORNSUN in their datasheet of CAN transceiver with integrated power. I have few questions regarding few components used there: What is the purpose of ...
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CAN: End-Of-Frame for detecting stuffing errors?

The end-of-frame consists of 7 recessive bits. It is often written that it is used to detect stuffing errors by a receiver. I also read that if the 7th bit is driven to dominant level, the transmitter ...
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50 views

Connecting two ports of arduino together

I want to implement the working of a CAN transceiver using Arduino. But the problem is - I have only one Arduino. So, I thought of sending and receiving signals using different ports of the same ...
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CAN Bus Hardware Design with 1000 nodes

I am looking to develop a CAN Bus System employing up to 1000 nodes on a single network. I am using an existing design based on STM32F072CB that has the CAN Controller embedded along with TJA1050 as ...
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136 views

Beaglebone Black CAN bus overlay does not work

I'm trying to use the CAN1 bus on the Beaglebone Black board (the pins at P9.24 and P9.26). First I tried the config-pin commands to change the pinmux mode from its ...
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80 views

Different canbus modules can work together?

Can ı use different canbus modules(vp230 and mcp2561) transmit and receive, respectively. long: I set up can transciever side vp230 based longan module(https://docs.longan-labs.cc/1030001/) with ...
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120 views

Help in deciding between RS485 or CAN [closed]

PROBLEM I'm building a robot control board to attach to a Raspberry Pi as an hobby. I like to have specialized boards for various functions, and I'm exploring solutions for the communication bus. In ...
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CAN Transceiver circuit problem with TJA1042T/3

I am a novice designer who recently started designing circuits. Using the STM32f407VGT MCU operating at 3.3V, using the CAN1TX(PB9) CAN1RX(PB8) pins, the circuit was configured by referring to NXP's ...
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Shownig RTNETLINK answers: Operation not supported while setting CAN bus modes

I'm new to CAN bus and I'm trying to write some data frame on CAN bus from a CAN node to another CAN node. I have enabled CAN device driver through my build source. But whenever I try to select mode ...
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How can 3.3v CAN-bus transceiver communicate with 5 volt CAN-bus transceiver?

I'm suing TCAN33x from Texas Instruments and it's a 3.3v CAN-bus tranciever. I have succeed to listen for CAN-bus messages from a 24V J1939 CAN-bus stepper motor. Very industrial. But I haven't ...

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