| Electronics > Projects, Designs, and Technical Stuff |
| CAN-bus msg validate, how? |
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| jhpadjustable:
--- Quote from: Jeroen3 on November 02, 2019, 07:53:36 pm ---To get your own interface you need the layer 1 tranceiver (eg: MCP2551) to get from a differential shared line to single ended split lines TX and RX. --- End quote --- For the lab, this might be good enough. |
| Chriss:
Ok. I will give a try to read the CAN bus of one of my ecu flaher. I never deal with CAN stuff on this level before. What is the proper way to connect the logic analyzer to the flasher tool? Do I need a 120 Ohm resistor first between CAN-H & CAN-L? Do I have to connect CAN-H & CAN-L to the logic analyanalyzer? Thank you. |
| Jeroen3:
You are not going to receive anything useful is you do not have at least two CAN controllers on the bus. Connecting only a logic analyzer will not work. CAN will error not-acknowledge. Yes, at least one 120 ohm is required for operation on your desk. In production each end of the bus requires the 120 ohm resistor. |
| Chriss:
Ok. Here is my new idea how to setup a bench CAN simulator, will this work or not? I have an Arduino Uno R3 If I buy this shield: https://s.click.aliexpress.com/e/4qkMTal2 I found this ecu simulator on github: https://github.com/AppSaloon/ecu-can-bus-simulator/blob/master/README.md So, if I would all this stich together and connect lets say one of my diag tool like VCDS or maybe a better option the ELM327, could I use my Loguc analyzer and play with this gadget? Or I need something more? Thanks. |
| Jeroen3:
ATMega based Arduino do not support this. You need a CAN controller. Available in STM32F042K6, STM32F446 , LPC1768, AT90CAN32, PIC18F458 and many other. But not ATMega. CPU -> CAN Controller -> GPIO -> CAN Transceiver -> CAN Bus H/L. Only the underlined bit is suitable for your logic analyzer. But a logic analyzer of little to no value with CAN bus, the signals are never wrong. The data is, and that is only visible in more complex software, like Busmaster. |
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