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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MCU receive CAN data after a while

I am using stm32f4 and sensor with my Canbus experiments. When I transmit canbus data to sensor, sensor send to some data as in below picture( green is Canbus H line, pink is CAN-Rx line) And blue is,...
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Using CAN with Teensy 4.1 is better than using RS-485 which requires extra converter?

I am using Teensy 4.1 and need to communicate with motor driver which supports CAN and RS-485. In teeny4.1 CAN is supported yet it requires CAN transceiver whereas if I want to use RS-485 I need to ...
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Can Tx-Rx Data Line

I am trying to see some data on the CANBUS line , I show the CANH and CANL data on the osciloscope line. And detect Rx line, When I show the Transmit message on the CANBUS line, I show the this data ...
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How to find the data length code CAN frame?

Question written as its I want to find the data length code of the CAN data frame. In our textbook we are given a formula in picture which bits do I have to include to this formula: Which bits do I ...
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Reading CAN Bus without a ground [closed]

I need your help to find a transceiver that can read or write data on a CAN bus using only CANH and CANL, without the ground of the System I am connected to. Just to be clear, I need something that ...
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CANBUS troubleshooting

I'm currently having some trouble communicating my motors to a Speedgoat real-time target machine. Setup: My current setup includes the Speedgoat IO691 (CANBUS) module (https://www.speedgoat.com/...
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Detecting activity on CANbus

I would like to ask for help designing a circuit to turn on a relay when there is CANbus activity in a vehicle. (sounds like other questions but with CAN) What I have so far is a SPST bistable ...
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Can CANopen coexist with CAN2.0B on the same bus?

I am new to CAN protocol so I have questions about combinations of CAN-Bus nodes on same network: Is it possible to communicate with two different devices one having CAN in Automation (CiA) CANopen DS ...
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What is the purpose of LIN broadcast 0x7F NAD?

This is something that is not clear to me from the LIN 2.2A spec which is publicly available. Consider a network with one LIN master and three LIN slaves, and a schedule table with a slot for master ...
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CANOpen SDO block transfer retry if timeouted?

I'm using the CanFestival CANOpen library (https://canfestival.org/) for a PC app that talks to a device via CAN bus. The device is CIA-301 compliant. I'm using SDO block transfers for device firmware ...
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Tap into CAN bus

I'm thinking about tapping into an existing CAN bus. I'm going to attach in a middle point, and I don't want to introduce any issue in the original bus. In order not to disturb the original bus with ...
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Why does my CAN bus always default to "bus-off"?

My project requires me to make use of a CAN bus, and an electronic dial as a node on the CAN bus. One version of the program I wrote for it worked perfectly, no problems here. I then went back to ...
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Using a FDCAN controller with a CAN transciever on the STM32 platform (G431KB)

I have a source of can messages connected to the SN65HVD232D CAN controller, which is then wired to a NUCLEO-G431KB via the FDCAN1 TX and RX pins. I confirmed with an oscilloscope/digital decoder that ...
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CAN-Physical Layer PtP

In a current design i have to form a Point-To-Point communications link in an industrial environment. Based on some research and thinkering i came up with the idea to use a CAN-Physical layer for this....
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Why I am seeing 120 ohms resistance in obd connector Pin6 amd Pin16 and at ABS connector resistance between can+ and can- shows 60 ohms. Why?

I am seeing a resistance of 120 ohms between CAN high and CAN low at the OBD Connector between pin 6 and pin 14. I also checked the can bus resistance at the ABS/ESP module connector and it shows 60 ...
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candump and cansniffer are working but cansend is not working on Raspberry Pi + RS485 CAN HAT (MCP2515)

I connect it at 500k bitrate. Both candump and cansniffer are working, receiving a lot of messages. I've pinned down the packet ...
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CAN bus fault protection

Question: Is there a way to implement with discrete components the 70V CAN bus fault protection found in some transceivers, such as TCAN1051H-Q1 ? Background: We are using the CAN transceiver ...
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What can this CAN bus like protocol be?

I am currently probing what seems to me the CAN bus twisted pair of my car. But the signals are not what I expect. One of the pair is like a typical CAN HI signal, however the idle state is a 0V and a ...
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CAN bus wrong bit rate calculation - stm32f107 keil drivers

I am using keil drivers to use CAN bus on an STM22F107. The method below is used to set CAN baud rate. ...
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2 answers
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CAT6 for both RS485 and CAN in same cable

I have two devices which need to talk to two controllers about 60m away in the garden.One uses RS485 and one uses CAN. I have to run armoured CAT6 for this and wondering if I can use the same run for ...
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STM32 FDCAN Duplicate Messages

I'm working with the STM32L552ZEQ, and I'm noticing that it is sending duplicate CAN transmissions. I have two threads, one that adds transmissions to a FreeRTOS queue, and one that spins and ...
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STM32F107 CAN software driver does not work

I am using ST drivers to use CAN bus on an STM22F107 according to the code below. It does not work. The code is as below and is available here. ...
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Protect bus and remaning bus-attached devices for bus-attached device failure (CANBus)

What are options to protect CANBus from failure of device connected to bus? For example if CAN Transceiver pulls bus high or low. Or some other sort of electronics failure. Thx
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Best approach to program a PLC using dbc file? (CAN communication)

I'm pretty new using CAN Communication but I need to program a Phoenix Contact PLC in Structured Text. The PLC should communicate with a motor that uses CANOpen protocol. The only resource I have is ...
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How CAN devices should be connected

I am planning on connecting CAN devices from one single hub - where they are connected in parallel. Though on internet I found that most examples use 'device to device' connection. Is there a ...
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CAN bus idle voltage too low

I'm testing a CAN bus circuitry based on MAX3051. VCC is 3.3V Two nodes are only connected on the bus. Termination resistors 120 Ohm are on each end of the bus. When the bus is in idle state (no one ...
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Problem interfacing SD card module + CAN Bus MCP2515 module simultaneously on arduino UNO

I am trying to log data received on CAN bus to SD card using arduino UNO. each module works perfectly on its on, but when joining both modules together the CAN bus receives data normally but the SD ...
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1 answer
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CAN FD Bit Stuffing on the boundary between DATA and CRC fields

CAN FD specification states that there shall be a fixed STUFF-BIT before the first bit of the CRC SEQUENCE. However, there is an edge case according to this statement when the DATA field ends with a ...
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4 votes
1 answer
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Troubleshooting CANbus 2B comms on ESP32-WROVER-based custom PCB (ABOVE WARN, ERR PASSIVE, BUS ERROR)

I am building an ESP32 WROVER-based custom PCB which includes CANbus 2B communications. This PCB is a copycat of my breadboard project. Though on my breadboard version, the CANbus works like. charm, ...
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CAN/J1939 Bus Protocol - Difference between Command and Request

In a CAN Bus, there are no Master/Slave configurations. However, I've seen multiple uses of both command signals as well as request signals. Although they seem to be interchangeable, wouldn't "...
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Getting 45.6 Ω when it should be 60 or 120 Ω on CAN bus

We have a 2011 Chrysler 6.1L Hemi SRT. We can not get any diagnostic reading at the DLC or OBDII port. We have checked all the wiring, fuses etc. Our readings at the DTC connector are as follows: CAN ...
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CAN bus termination resistor

I'm trying to design a CAN device where the user can select which device is the beginning/end device and activate the 120 ohm resistor accordingly. I've seen some examples using a switch, but I'm ...
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Why does the CAN bus need termination resistors and other buses don't?

I've been working on a project based on CAN bus communication. In the past, I also worked on projects with other high-speed buses, for example SPI. Although SPI is a high-speed bus it does not need ...
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Using CAN bus on a NucleoH743 with Mbed

CAN bus is not working on my project. We are using a Nucleoh743 (STM32h743) programming it with mbed (Mbed OS 6.13) I have made sure the bus is properly made, with the correct termination resistors, ...
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Home automation using CAN bus

I am planning to make a prototype for wired home automation devices, and I am thinking of using CAN bus for communication between nodes and Gateway. The way I am planning to build it, there is one ...
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3 votes
1 answer
102 views

Different CAN-BUS specs on the same bus

I have several questions about different combinations of CAN-Bus nodes that are able to work together with realiability: CAN2.0A and CAN2.0B nodes can work on the same bus at the SAME speed? CAN2.0A ...
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The role of the VSPLIT in this CAN transceiver

I want to know how the VSPLIT (Pin 11) in the IC NCV7341 works and what its real effects in the citcuit are. In the data sheet it says it is used to stabilise the CAN signals, but how? What does &...
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CAN BUS : CAN_BUSY returned but other node recieved the previosus message

I have two can nodes in a CAN bus. node1 send messages periodically , node2 received only the first message (I can check with a CAN tool) for the first message, CAN_OK is returned for send routine. ...
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Protect RJ45 CAN from POE

I'm trying to design a PCB with CAN Bus connection with STM32 (will be using a CAN transceiver) where we're using RJ45 for the CAN port. One of the main concern is what if the user plug in a Power ...
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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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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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2 answers
101 views

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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1 answer
80 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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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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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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2 votes
1 answer
57 views

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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3 answers
947 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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2 answers
132 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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2 votes
2 answers
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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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2 answers
444 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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