AM3358: DCAN loopback questions

Chetan Patel46

Part Number: AM3358

There are two types of loopback supported in AM335x. (1) Loopback(Internal) and (2) External Loopback.

This question pertains to both loopback types: Does DCAN module set RXOK bit in ES register when any of the loopback modes are enabled ?

It was observed on AM3358 and J6 processors that RXOK bit works as expected when DCAN is operating in normal mode but the DCAN module does not set(or reset) RXOK when internal loopback mode is enabled. AM335x TRM document does not talk anything about this.

Does TI have any documentation(other than TRM) on what all things that DCAN module do and don't do when loopback mode is enabled/disabled.

over 6 years ago

0 melissaw over 6 years ago

TI__Genius 15910 points

Hi,

Your observations are accurate. The RXOK bit will not be set when any of the loopback modes are enabled.

To my knowledge, there isn't any additional documentation addressing things that DCAN module do and don't do when loopback mode is enabled/disabled.

Regards,

Melissa

0 Chetan Patel46 over 6 years ago in reply to melissaw

Prodigy 250 points

Great. Thank you for clarifying that. Another question on external loopback. Are there any other steps involved in enabling external loopback mode compared to internal loopback mode ?

Here are the upper level steps that I follow to test loopbacks. Internal loopback works fine but for external loopback we do not get interrupted at all. When embedded software sends a message, I see that transmit was requested but no transmit complete interrupt gets fired.

Steps to enable internal loopback:(1) Enable test mode (2) Enable internal loopback mode

Steps to enable external loopback (1) Enable test mode (2) Disable internal loopback mode (3) Enable external loopback mode.

0 melissaw over 6 years ago in reply to Chetan Patel46

TI__Genius 15910 points

Hi Chetan,

I'm not aware of other steps. Are you seeing any activity on the DCAN_TX pin?

Also, you may find this e2e post helpful-- https://e2e.ti.com/support/microcontrollers/c2000/f/171/t/686198?TMS320F28377S-Difference-between-Loopback-mode-and-External-Loopback-mode-in-CAN-module-in-TMS320F28377S. It's about another TI device, but it looks like the CAN module is similar to AM335x's DCAN module.

Regards,

Melissa

0 Chetan Patel46 over 6 years ago in reply to melissaw

Prodigy 250 points

No. I do not see anything on TX pin. Also, that thread did not help.

Processors

Processors forum

AM3358: DCAN loopback questions