Hei all,
After getting the LLWU functionality via an external Pin (LLWU_P6) to work, I still struggle to understand some features when using the LLWU.
I have a Codewarrior project with Processor Expert, running on a FRDM-KL26Z development kit. LLWU_P6 is used to receive a ready signal from an ADC when the ADC is done with its conversion. Until then the MCU should save some power and be in sleep mode.
Case 1: LED on, MCU put to sleep, LED off in Cpu_OnLLSWakeUpINT
The function that sets the MCU to stop mode:
static uint8_t SpiAdc_WaitForReadySignal()
{
/* Interrupt based solution
* The MCU is put into STOP mode (LLS - Low Leakage Stop), and is waken up
* using the SPI MISO / Ready signal from the ADC. The Ready pulse wakes up
* the MCU from STOP mode using the LLWU (Low Leakage Wake Up) functionality.
* This is configured in PE, and currently LLWU_P6 /PTC1 is used for the Ready signal.
*/
Red_LED_ClrVal(Red_LED_DeviceData); /* Turn on red LED */
Cpu_SetOperationMode(DOM_STOP, NULL, NULL);
return ERR_OK;
}
Events.c , where Cpu_OnLLSWakeUpINT is located:
void Cpu_OnLLSWakeUpINT(void)
{
/* Write your code here ... */
volatile uint32_t tmp;
tmp = Cpu_GetLLSWakeUpFlags();
Red_LED_SetVal(Red_LED_DeviceData); /* Turn off red LED */
}
This is how things look on the scope.
The green LED signal indicates the ADC readout procedure, the red LED indicated entering the sleep mode and exiting it again (see above in the source code).
Instead of turning of the red LED when entering Cpu_OnLLSWakeUpINT, it is only toggled, and never turned off.
Case 2: LED on, MCU put to sleep, LED off in same function
If the code for putting the MCU to sleep is changed to the following:
static uint8_t SpiAdc_WaitForReadySignal()
{
/* Interrupt based solution
* The MCU is put into STOP mode (LLS - Low Leakage Stop), and is waken up
* using the SPI MISO / Ready signal from the ADC. The Ready pulse wakes up
* the MCU from STOP mode using the LLWU (Low Leakage Wake Up) functionality.
* This is configured in PE, and currently LLWU_P6 /PTC1 is used for the Ready signal.
*/
Red_LED_ClrVal(Red_LED_DeviceData); /* Turn on red LED */
Cpu_SetOperationMode(DOM_STOP, NULL, NULL);
Red_LED_SetVal(Red_LED_DeviceData); /* Turn off red LED */
return ERR_OK;
}
The Cpu_OnLLSWakeUpINT then does nothing, essentially...
void Cpu_OnLLSWakeUpINT(void)
{
/* Write your code here ... */
volatile uint32_t tmp;
tmp = Cpu_GetLLSWakeUpFlags();
// Red_LED_SetVal(Red_LED_DeviceData); /* Turn off red LED */
}
And the scope picture of this event looks like this:
Again yellow is the SPI Ready signal, green shows the whole ADC readout procedure, and red LED signal is the time that the mcu is sleeping.
The one source code line turning off the red LED is the only source code line that was changed in the project.
- In case 1, how come the LED never gets turned off in Cpu_OnLLSWakeUpINT, even though the CPU clearly wakes up from its sleep? Is the Cpu_OnLLSWakeUpINT not executed?
- In case 2, what causes the two spikes on the red led signal, they happen 240µs before the yellow spikes on the SPI/Ready signal?
Thanks for your help!
Dominik
Hi,
I apologize for the late response, I was working on this issue but I have some problems to understand exactly the issues you are experimenting. Attached you will find an example I created to test this, I will explained later. First I want to give you some hints and ideas when working with LLS mode in Processor Expert and none Processor expert projects.
- It is not necessary to configure the PORT and GPIO registers for the Pin used as the wake up source. The pin pad is connected directly to the LLWU, then the LLWU is sensitive to the pin changes. This is because the PORT and GPIO registers remain static during LLS mode.
- In Processor Expert setting the External Pins is enough to say the LLWU that such pin will be a wake up source:
- When exiting LLS mode the code line before the GoToLLSMode instruction will be excecuted and after that the code will run normally.
- Is better to have a small code in the Interrupt Service Routine (ISR) then try to just set flags that will be checked after the ISR ends.
- Debug is not possible during LLS mode.
- When debugging the application, after the LLS mode enter the debug mode will be disconnected, then it is not possible to return to debug mode. In this case if you continue running the application without disconnecting the board after the Connection Lost message in CodeWarrior the MCU will be trying to restart the Debug mode and you application will not run normally. The recommend way to test the application is in standalone mode: after flashing the program into the device disconnect and connect again the board.
As I mentioned attached you will find a simple project I created to demonstrate the use of External pins to wake up the MCU from LLS mode.
The philosophy of the code is the next:
- Wait 5 seconds
- Leds Blue+Green are toggled.
- MCU moves to LLS mode
- Wait for a change in the Wake up pins. The pins are: PTC3 (connected to SW1), PTC5 (connected to J4[9]) or PTC1 (connected to J4[12]).
- When the MCU is waken up from one of this sources the Cpu_OnLLSWakeUpINT is called and set some flags.
- The code returns to the line after the Cpu_SetOperationMode(DOM_STOP,NULL,NULL) function and evaluates the flags: If PTC3 was the source Blue led is toggled, if PTC5 was the source Green led is toggled and if PTC3 nor PTC5 (this means PTC1 or other source) were the source Red led is toggled.
- The steps are repeated.
Please refer to the attached example for better explanation.
If you have any question please do not hesitate to ask.
Hope this information can help you
Best Regards,
Adrian Sanchez Cano
Technical Support Engineer
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