Multiple Arduino CAN nodes create form error on CAN bus

[surban2364]

I am using 5 Arduino megas with DF Robot CAN shields on each of them. All of them are on the same CAN bus. I am sending messages on the CAN bus using Vector VN1630A.

Each of the Arduinos are receiving messages using code receiveCheck.ino from DF Robot: DFRobot_MCP2515/examples/receiveCheck/receiveCheck.ino at 7c8a7a98c15f99712a46445ad505f2d065138c8c · DFRobot/DFRobot_MCP2515 · GitHub

With 3 of these nodes on the same CAN channel, I am able to communicate to each of them with no error.

Once 4 nodes are on the same CAN channel, I receive a form error on the CAN channel:

The error stops all communication on the CAN channel. I have added this filter to each Arduino:

CAN.initMask(MCP2515_RXM0, 0, 0x05FF);                         // there are 2 mask in mcp2515, you need to set both of them
CAN.initMask(MCP2515_RXM1, 0, 0x05FF);

/*
 * set filter, we can receive id from 0x0534
 * // there are 6 filter in mcp2515,so it can filter six id,i.e.0x04~0x09.
 */
CAN.initFilter(MCP2515_RXF0, 0, 0x0534);

There was no change after adding this filter. Everything I know about these CAN error messages points to a hardware issue. Any help is appreciated.

Hardware details:
Vector: VN1600 Family - Network Interfaces for CAN, CAN FD, LIN, K-Line, J1708 and IO | Vector
Arduino Mega: https://www.amazon.com/ELEGOO-ATmega2560-ATMEGA16U2-Projects-Compliant/dp/B01H4ZLZLQ/ref=sr_1_2_sspa?dib=eyJ2IjoiMSJ9.mz1D_mMr7EDgH2SXGDwsrcr8OpUS1dbM5BUDhRY6ADdSL60H8dDf948EJ05ngi2Xwc5iytHKFRx-cGqzvFr2BWq-BCdGj1-YdsaZVRddxPZfhGmiBOcxt6PAma839xp7hxh_CFPS9-ZjCrT5dqWCf_xmNtOur1tLFosabZk64kASqbd0y9dpO1k1mRNw-THPkATh3DIx0xBeSnO1XWCGLJ6LlxZskJAxJHQ_zGwDHhg.HL0ZZcykHQWbUOEFFS0m_CEfzZj0jU1dUIaHNMUFQ1o&dib_tag=se&hvadid=174256732038&hvdev=c&hvlocphy=9016994&hvnetw=g&hvqmt=e&hvrand=199518857279254025&hvtargid=kwd-24718511749&hydadcr=24658_9648989&keywords=arduino+mega+2560&qid=1708534323&sr=8-2-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1
CAN Shield: Arduino CAN BUS Shield - DFRobot

[mikb55]

@surban2364

DF Robot CAN shield

The schematic shows a 120 ohm termination resistor labelled R2.
A bus only works properly when there are 2 resistors, one at each end.
You need to desolder the excess resistors.

[gilshultz]

@surban2364

CAN shields on each of them.

mikb55 is correct, CAN is a 60 Ohm bus. Remove all termination jumpers except the ones at the physical ends of the bus. After that you should be able to plug in at least a dozen more if the termination is not enabled.

[surban2364]

Well, that makes things easy. Thank you for your response... you made my day

After depopulating each R2 resistor on the CAN shields the issue is resolved.