MSPM0L1228: How to enable uart interrupt in low power mode

Sho Takayama

Intellectual 390 points

Part Number: MSPM0L1228
Other Parts Discussed in Thread: MSPM0-SDK, MSPM0G3507, LP-MSPM0L2228

Tool/software:

Hi,

I disabled the Async Clock Request of the UART to allow the MCU to enter low power mode (power policy Standby1).

However, as a result, I can no longer receive UART interrupts when a character is received.

My expectation is to exit low power mode when a character is received using a UART interrupt.

UART_0_INST->GPRCM.CLKCFG = 0xA9000100;
UART_1_INST->GPRCM.CLKCFG = 0xA9000100;
UART_2_INST->GPRCM.CLKCFG = 0xA9000100;

9 months ago

0 Helic Chi 9 months ago

TI__Mastermind 19947 points

Hi, Sho

please refer to https://www.ti.com/lit/ds/symlink/mspm0l1228.pdf

ULPCLK is dis in standby1, please use standby0.

Regards,

Helic

0 Sho Takayama 9 months ago in reply to Helic Chi

Intellectual 390 points

Hi Helic Chi

Can I use the asynchronous fast clock to wake up from Standby1 when a character is received through a UART interrupt?

I also tested Standby1 with GPIOA as a switch. The interrupt only occurs when the switch is pressed, causing the MCU to exit Standby1.

But it does not apply to the UART. As described above, if I don't disable the UART asynchronous fast clock (UART_0_INST->GPRCM.CLKCFG = 0xA9000100), the MCU cannot enter low power mode.

0 Helic Chi 9 months ago in reply to Sho Takayama

TI__Mastermind 19947 points

Hi, Sho

Sho Takayama said:
Can I use the asynchronous fast clock to wake up from Standby1 when a character is received through a UART interrupt?

Yes.

Sho Takayama said:
I also tested Standby1 with GPIOA as a switch.

GPIO interrupt can work in all low power mode, except shutdown.

Sho Takayama said:
But it does not apply to the UART. As described above, if I don't disable the UART asynchronous fast clock (UART_0_INST->GPRCM.CLKCFG = 0xA9000100), the MCU cannot enter low power mode.

Maybe there are interrupt still set in UART, please try wo observe the UART->RIS, MIS IMASK register,

before entering LPM, please only keep UART Rx interrupt enable and keep Rx interrupt clear.

Regards,

Helic

0 Sho Takayama 9 months ago in reply to Helic Chi

Intellectual 390 points

Hi Helic Chi

Helic Chi said:
Maybe there are interrupt still set in UART, please try wo observe the UART->RIS, MIS IMASK register,

before entering LPM, please only keep UART Rx interrupt enable and keep Rx interrupt clear.

I sent an example code.

In sysconf, UART0 is added but not used. The SysTick timer is still operating in Standby1 mode without disabling the UART asynchronous fast clock.

Could you check this and guide me on how to enter Standby1 mode with the SysTick timer stopped, then use the asynchronous fast clock to wake up from Standby1 when a character is received through a UART interrupt?

sysctl_power_policy_sleep_to_standby_LP_MSPM0L2228_nortos_ticlang.zip

0 Helic Chi 9 months ago in reply to Sho Takayama

TI__Mastermind 19947 points

Hi, Sho

Please refer to this code example in MSPM0-SDK:

C:\ti\mspm0_sdk_2_03_00_07\examples\nortos\LP_MSPM0G3507\driverlib\uart_echo_interrupts_standby

I have test it on launchpad, Both LP-MPSM0G3507 and LP-MSPM0L2228 work well.

Need to change LPM mode from STANBY0 to STANBY1 in syscfg.

Regards,

Helic

0 Sho Takayama 9 months ago in reply to Helic Chi

Intellectual 390 points

Hi Helic Chi

I tested uart_echo_interrupts_standby on LP-MSPM0L2228 and it works well.

(I also added SYSTICK to observe the LPM mode. And it only occurs when the UART interrupt is being processed.)

But,

When I change the RX and TX of UART from PA11/PA10 to PA1/PA0, SYSTICK always occurs even without a UART interrupt.

I am using pins PA1/PA0 for UART communication. How can I make the MCU's operation with PA1/PA0 behave the same as with PA11/PA10?

0 Helic Chi 9 months ago in reply to Sho Takayama

TI__Mastermind 19947 points

Hi, Sho

PA0 and PA1 are ODIO, need external pullup resistor.

Regards,

Helic

0 Sho Takayama 8 months ago in reply to Helic Chi

Intellectual 390 points

Hi Helic Chi

Helic Chi said:
PA0 and PA1 are ODIO, need external pullup resistor.

It works well. Thanks!

By the way, could you tell me why ODIO requires an external pull-up resistor?, and why SYSTICK still occurs even without a UART interrupt in LPM mode if external pull-up resistor is not used?

+1 Helic Chi 8 months ago in reply to Sho Takayama

TI__Mastermind 19947 points

Hi, Sho

Sho Takayama said:
By the way, could you tell me why ODIO requires an external pull-up resistor?

Please refer to TRM IOMUX section for ODIO M0 internal circuit schematic, IDIO do not have the ability to output a high level without external pullup.

Sho Takayama said:
why SYSTICK still occurs even without a UART interrupt in LPM mode if external pull-up resistor is not used?

May caused by UART keep wakeup the CPU when ODIO keep low.

Regards,

Helic

0 Sho Takayama 8 months ago in reply to Helic Chi

Intellectual 390 points

Hi Helic Chi

Thanks so much!

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MSPM0L1228: How to enable uart interrupt in low power mode