MSP430F5507: No communication start of UART at low temp(0℃)

Tohru Sakuma

Part Number: MSP430F5507

My customer is facing the issue of "no communication start of UART at low temp(0℃)" on their system.

The UART communication using the USCI port did not start when the power was turned on occurred,

UART is working correctly at room temperature (23 ° C) or high temperature (45 ° C), but it occurs at low temperature.

I have attached the photo of the waveform observed by the oscilloscope at power-on,
Yellow: A signal that outputs Hi / Lo inversion every 200ms while operating with PU.1.
Blue and green: UCA1TXD, after this it should respond after boot, but the signal is falling to Lo (Hi-Z)
Red: UCA1RXD receives startup notification from the system's Main CPU after this

The customer expect the output of TXD drops to Lo 2s after the power is turned on, which is a clue to the problem phenomenon.

Could you advise what we should check like register setting and clock tree selection ?

since we request customer to do it .

over 3 years ago

0 Winter Yu over 3 years ago

TI__Genius 12315 points

Hello,

What's the current clock source of UART?

Could you monitor this clock?

0 Tohru Sakuma over 3 years ago in reply to Winter Yu

TI__Prodigy 580 points

The UART clock source uses the internal clock, and the waveform cannot be acquired.

As one correction

Although it is set to UART at startup, the output of TXD becomes High impedance at low temp(0℃)

(The attached waveform has dropped to Low because Pull Down is on the receiving side of TXD).

The customer would like to know possibility related to USCI31 of errata.

Do you think about this ?

0 Winter Yu over 3 years ago in reply to Tohru Sakuma

TI__Genius 12315 points

Hello,

For USCI31, customer need reset USCI-UART (software reset via UCSWRST) during an ongoing receive operation.

So customer has this operation in their code?

The UART clock source uses the internal clock, and the waveform cannot be acquired.

Which clock? SMCLK?ACLK?

0 Shota Mago over 3 years ago in reply to Winter Yu

TI__Expert 6580 points

Hi Winter-san

I'm an FAE in charge of same customer with Sakuma-san.

Thank you for supporting this post.

I'm checking that which internal clock is used and if their code include operation related to USCI31.

Meanwhile, they would like to know why TXD output becomes Hi-Z at low temperature(0℃).

Do you have any idea of this phenomena?

Best regards,

Shota Mago

0 Tohru Sakuma over 3 years ago in reply to Winter Yu

TI__Prodigy 580 points

We have got response about your question.

Which clock? SMCLK?ACLK?

-They use SMCLK for UART.

So customer has this operation in their code?

-They don't use such a operation related to USCI31 of errata.

If you can give some suggestion to find root cause, it will be very helpful.

T.Sakuma

0 Winter Yu over 3 years ago in reply to Tohru Sakuma

TI__Genius 12315 points

Could you output the SMCLK via P2.2 and see if it's status when UART communication failed at low temp(0℃)?

**Attention** This is a public forum

MSP low-power microcontrollers

MSP low-power microcontroller forum

MSP430F5507: No communication start of UART at low temp(0℃)