LAUNCHXL-F28379D: CAN CHIP QUERY

VIKRAM ROY CHOWDHURY

Part Number: LAUNCHXL-F28379D
Other Parts Discussed in Thread: TMS320F28379D

Hello

My name is Vikram and I have a tms320f28379D docking station. I am trying to get CAN communication and have connected transceiver chip of SN65HVD233DR in my breakout board. First, I am little confused that in this chip I have something called an LBK port which is for loopback. Since I do not have any loopback I have grounded it. Is it correct? Then I have RS and for high speed mode I have also grounded it. Then CAN L and CAN H are terminated on a 120 ohm resistor. Then I am trying to connect this CAN L and CAN H on a TMS320f28379D launchpad that has SN65HVD234DR transceiver chip. The issue I have is when I use my code and use two launchpads I can successfully accomplish CAN communication as expected from my code application. But with a docking station and launchpad I do not see any CAN communication. What can be the possible reason? Can it be that docking station breakout board has SN65HVD233DR and launchpad has SN65HVD234DR that is why they are not communicating. I am actually pretty new to CAN so I am unsure how to fix this.

Can anyone kindly help me to solve this issue.

Thank you in advance.

over 3 years ago

0 Hareesh Janakiraman over 3 years ago

TI__Guru* 95315 points

VIKRAM ROY CHOWDHURY said:
Since I do not have any loopback I have grounded it. Is it correct?

Yes.

VIKRAM ROY CHOWDHURY said:
Then I have RS and for high speed mode I have also grounded it.

Better to use a 10K series resistor or higher. Else the slew rate may be very slow.

VIKRAM ROY CHOWDHURY said:
But with a docking station and launchpad I do not see any CAN communication.

Note that the input clock to the 28379D device is different on the launchpad (10 MHz) and the ControlCard (20 MHz). You need to account for this in your code. This is probably the root cause of the issue you are facing.

VIKRAM ROY CHOWDHURY said:
Can it be that docking station breakout board has SN65HVD233DR and launchpad has SN65HVD234DR that is why they are not communicating.

No, you are free to use any transceiver from any company. That does not matter.

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to Hareesh Janakiraman

Prodigy 70 points

Thank you for your reply. I just tried that but did not fix it. However, I am trying something with a scope in the lab. Where I have connected the canh and canL to the oscilloscope for the launchpad. The same code is burnt on the docking station dsp f28379d and I directly connected to the gpio and ground I just see 3v3. What can be the possible cause

0 Hareesh Janakiraman over 3 years ago in reply to VIKRAM ROY CHOWDHURY

TI__Guru* 95315 points

VIKRAM ROY CHOWDHURY said:
The same code is burnt on the docking station dsp f28379d

You cannot use the same code on LP and CC due to the difference in i/p clock values. Another possible area of difference is the GPIO pins. Are you using the same GPIO pins for the CANTX & CANRX pins on both boards?

In general, it is easier to trigger the scope on CANTX and CANRX pins rather than CAN_H & CAN_L pins.

Please refer to www.ti.com/lit/SPRACE5. I have provided all the debug tips you need to debug an issue like this. I have also clearly explained how to do the GPIO re-mapping.

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to Hareesh Janakiraman

Prodigy 70 points

Thank you also this is the schematic of my can chip can you kindly let me know your thoughts

Thank you in advance.

0 Hareesh Janakiraman over 3 years ago in reply to VIKRAM ROY CHOWDHURY

TI__Guru* 95315 points

Sorry, I cannot make out anything from the image. All the text is blurred.

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to Hareesh Janakiraman

Prodigy 70 points

I apologize for this kindly find the attached pdf that has the schematic with the top left and bottom left being the can chip connectionsInterface_v7.pdf

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to VIKRAM ROY CHOWDHURY

Prodigy 70 points

Also one more point I used one of the example codes 'can_ex2_loopback_interrupts' it shows pulses every 1 sec on the GPIO pin however, when I gave them as input to the can TX and CANRX based on the code GPIO settings, I could see only 0 on the canH and CAN L. Kindly help.

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to VIKRAM ROY CHOWDHURY

Prodigy 70 points

Does it mean that since I am seeing all 0 for this example my CAN chip is gone (burnt)

0 Hareesh Janakiraman over 3 years ago in reply to VIKRAM ROY CHOWDHURY

TI__Guru* 95315 points

Vikram,

The connection between the MCU and the CAN transceiver is very straightforward and is shown in all Launchpad schematics. Please go through my debug tips in SPRACE5. It is hard to debug this without access to the hardware.

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to Hareesh Janakiraman

Prodigy 70 points

Thank you for your suggestion I have everything as per schematic only I am using 233Dr and launchpad used 234DR and I grounded RS to direct ground that should not be an issue as you mentioned earlier. Finally, thank you for sharing the link to your document I am reading it just wanted to know from your perspective if the CAN connection as per the schematic I shared may be an issue. I apologize as I am very new to CAN and doing it for the first time so I have pretty trivial queries.

0 Hareesh Janakiraman over 3 years ago in reply to VIKRAM ROY CHOWDHURY

TI__Guru* 95315 points

I am unable to make out anything from your schematics. I need to see the connection from the CANTX/CANRX pins (of MCU1) through the transceiver to the other transceiver and then to the CANTX/CANRX pins of the other MCU (MCU2). The connections are really very simple. See fig 1-1 in www.ti.com/lit/SPRACU9. It is a simple wiring diagram. For details on the connections below, all you need to do is to refer to the LP schematic.

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to Hareesh Janakiraman

Prodigy 70 points

Thank you for your reply. I again apologize and attach my connection diagram with this text. Can you kindly let me know if I made something wrong. As the board is already printed it will be very difficult to change.
Thank you in advance.

0 Hareesh Janakiraman over 3 years ago in reply to VIKRAM ROY CHOWDHURY

TI__Guru* 95315 points

120 ohm terminator is needed at the output of both transceivers.

On the LP, CAN pins are GPIO12 and GPIO17.

All inputs on the MCU can only handle 3.3v. I noticed some 5v pull-ups in your circuit.

0 VIKRAM ROY CHOWDHURY over 3 years ago in reply to Hareesh Janakiraman

Prodigy 70 points

Thank you for letting me know yes the LP is at GPIO 12 and and GPIO 17 and also there was by mistake a 5V pull up on the GPIOs which I initially connected but now disconnected

But initially I powered it up with 5 V can it burn the chip

0 Hareesh Janakiraman over 3 years ago in reply to VIKRAM ROY CHOWDHURY

TI__Guru* 95315 points

VIKRAM ROY CHOWDHURY said:
But initially I powered it up with 5 V can it burn the chip

No, it will not burn the chip right away, but will definitely create a long-term reliability risk.

Focus on these 3 areas:

The clock speed on the CPU: You can run the simple transmit example, capture the bit-stream on the scope, look at the bit-width to verify whether the device is indeed running at the desired clock-speed.
Whether the correct GPIO pins are used: The GPIO pins your code is using should match the GPIO pins you have used for the CAN connection.
The connection between the two nodes: SPRACU9 shows the connection at a top-level and the LP schematics shows the finer details.

I have also explained this process in a video: https://training.ti.com/getting-started-dcan-module

Good luck.

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LAUNCHXL-F28379D: CAN CHIP QUERY