topic Error in Multi-Rate Timer (MRT) with multiple channel in LPC Microcontrollers

Error in Multi-Rate Timer (MRT) with multiple channel

hemanthvasista — Thu, 23 Jul 2020 08:42:28 GMT

Hello ,

I am working on the LPC546xx based device. I tried using Multi-Rate Timer (MRT) with multiple channel.

When I configure either of one channel, they work fine individually.
But when I enable both channel, channel-0 is interrupted at different time and no interrupt is generated on channel-1.

Below is code snippet

    /* mrtConfig.enableMultiTask = false; */
    MRT_GetDefaultConfig(&mrtConfig);
    /* Init mrt module */
    MRT_Init(MRT0, &mrtConfig);
    /* Setup Channel 0 to be repeated */
    MRT_SetupChannelMode(MRT0, kMRT_Channel_0, kMRT_RepeatMode);
    MRT_SetupChannelMode(MRT0, kMRT_Channel_1, kMRT_RepeatMode);
    /* Enable timer interrupts for channel 0 */
    MRT_EnableInterrupts(MRT0, kMRT_Channel_0, kMRT_TimerInterruptEnable);
    MRT_EnableInterrupts(MRT0, kMRT_Channel_1, kMRT_TimerInterruptEnable);
    /* Enable at the NVIC */
    EnableIRQ(MRT0_IRQn);
    MRT_StartTimer(MRT0, kMRT_Channel_0, 22000);       //100us interrupt
    MRT_StartTimer(MRT0, kMRT_Channel_1, 220000); //1ms interrupt

The ISR is as below:

void MRT0_IRQHandler(void)
{
   if(MRT_GetStatusFlags(MRT0, kMRT_Channel_0))
   {
       MRT_ClearStatusFlags(MRT0, kMRT_Channel_0, kMRT_TimerInterruptFlag);
       APP_LED_TOGGLE;
   }
   else if (MRT_GetStatusFlags(MRT0, kMRT_Channel_1))
   {
       MRT_ClearStatusFlags(MRT0, kMRT_Channel_1, kMRT_TimerInterruptFlag);
       APP_LED_TOGGLE_1;
   }
/* Add for ARM errata 838869, affects Cortex-M4, Cortex-M4F Store immediate overlapping
exception return operation might vector to incorrect interrupt */
#if defined __CORTEX_M && (__CORTEX_M == 4U)
    __DSB();
#endif
}

regards,
Hemanth

Re: Error in Multi-Rate Timer (MRT) with multiple channel

Omar_Anguiano — Tue, 28 Jul 2020 17:42:39 GMT

Hello Hemanth S

When channel 1 interrupts channel 0 also gets the interruption. I suggest you add a counter in the interruption on channel 0, when it reaches 1ms, the interruption of the channel 0 is disabled with "MRT_ClearStatusFlags" in order to enter the interruption of channel 1.

Another thing I can suggest is to do this comparison in the "if" sentence

If( 0x3 == MRT_GetStatusFlags(MRT0, kMRT_Channel_0) )

Let me know if this is helpful, if you have more questions do not hesitate to ask me.

Best regards,

Omar

Re: Error in Multi-Rate Timer (MRT) with multiple channel

hemanthvasista — Wed, 29 Jul 2020 06:35:34 GMT

Thanks for you inputs Omar.

Add of the below line solved the issue:

If( 0x3 == MRT_GetStatusFlags(MRT0, kMRT_Channel_0) )

regards,

Hemanth