TMS320F28335: Why did BRKDT and FE happen unexpectedly often

Wayne Huang

Part Number: TMS320F28335

Dear Champs,

I am asking this for our customer.

They use SCI at 115200 bps and use RXBKINTENA as the only ISR for testing.

On SCI RX pin, they could see the RX bauds were correct from oscilloscope, but from F28335 SCI, it often generated BRKDT and FE.

They could reset this by SW RESET, but the frequency (around 1 time out of 10 sending bytes) of BRKDT and FE was too high and troubled them.

They wonder why there were BRKDT and FE but from oscilloscope on the scope, they did not see anything wrong.

Do you have any suggestion how they can debug and clarify this?

Wayne Huang

over 3 years ago

0 Marlyn Rosales Castaneda20 over 3 years ago

TI__Mastermind 25210 points

Hi Wayne,

Thank you for the question.

Would it be possible to provide scope captures of the communication to showcase the expected baud rate is met for the two devices and the data sent. It would also be nice to toggle a GPIO upon a break detect/FE condition to show where in the communication the SCI module flags these errors.

How many stop bits are being used?

Best Regards,

Marlyn

0 Wayne Huang over 3 years ago in reply to Marlyn Rosales Castaneda20

TI__Genius 16435 points

Dear Marlyn,

The user changed a RS485 transceiver and drastically improved this, so it seems high-freq. noise would be the cause.

They are clarifying and will let us know if any further question.

Do you think it's good to use GPIO input qualification to deal with such high-freq. noise on pin SCI RX?

Wayne Huang

+1 Marlyn Rosales Castaneda20 over 3 years ago in reply to Wayne Huang

TI__Mastermind 25210 points

Hi Wayne,

Wayne Huang said:
The user changed a RS485 transceiver and drastically improved this, so it seems high-freq. noise would be the cause.

Thank you for the insight.

Wayne Huang said:
Do you think it's good to use GPIO input qualification to deal with such high-freq. noise on pin SCI RX?

Typically for SCI it is advised/ highly recommended to use asynchronous qualification mode. If you don't this could interfere with how the SCI is sampling each bit.

We list it this in our troubleshooting guide: https://e2e.ti.com/support/microcontrollers/c2000-microcontrollers-group/c2000/f/c2000-microcontrollers-forum/1031947/faq-my-c2000-sci-is-not-transmitting-and-or-receiving-data-correctly-how-do-i-fix-this

Best Regards,

Marlyn

C2000™︎ microcontrollers

C2000 microcontrollers forum

TMS320F28335: Why did BRKDT and FE happen unexpectedly often