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Part Number: SN65HVD230
HI! I've started working with a board already developed and needed to implement CAN protocol on a non-TI MCU. I've tested first an internal loop to get the libraries working and then, when I tried to output and transmit on CANP and CANH differential signals, I couldn't get anything. So I started testing the modules. Here's the schematic implemented:
I measured CANTXD and CANRXD signals outside the microcontroller, and are correct, and are getting correctly to pins 1 and 4 of the SN65HVD230:
Then I measured the device's differential output at pins 6 and 7 and this is what I got:
I measured the Common Mode Line Filter's output too, but still, SN65HVD230's output doesn't seem right to me. I would appreciate any tips or ideas regarding what to check here, so I can keep testing this module.
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In reply to Eric Schott48:
thanks for the reply. I'll see what I can do about C20 and C21.
To answer your questions, the only device connected to the bus is a development board, directly connected to this custom board. This is the setup:
In Figure 2, Channel 1 is TxD and Channel 2 is RxD. In my previous tests running only CAN bus on the development board, I got the same results, even though it wasn't connected to any other devices. What I mean is that RxD was exactly the same as TxD although no other device was transmitting, since there was no other device connected.
Anyways, I still don't have any signal after R18 and R21, and doesn't matter if anything is connected to the bus, since signals don't reach CAN_P and CAN_N pins:
In reply to Franco Polo:
As an update, I found that when one of the modules (one with an Ethernet connector and two CAN connectors) is attached to the circuit through a terminal strip, then every signal is connected to ground. Here are CAN_P and CAN_H signals after detaching the module:
I belibeve then, that this is my problem.
Thanks for the help!
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