topic Re: LPC845 SCTimer/PWM in LPC Microcontrollers

LPC845 SCTimer/PWM

keyzet_89 — Tue, 10 Sep 2019 14:51:34 GMT

Good day.
For the initial setup of the LPC845, I use MCUXpresso Config Tools. I need to configure SCTimer/PWM as PWM in two outputs and multiple events mode (OUT_0 use 2 events, OUT_1 use 4 events). All events is "Match event only". The program throws an error "Number of events exceeds 8 events supported by peripheral SCT0 (each PWM signal internally allocates 2 events)." Is it true? Or can I configure multiple events on one output manually? For example:

const sctimer_pwm_signal_param_t SCTimer_0_pwmSignalsConfig[2] = {
{
    .output = kSCTIMER_Out_0,
    .level = kSCTIMER_LowTrue,
    .dutyCyclePercent = 0
},
{
    .output = kSCTIMER_Out_1,
    .level = kSCTIMER_LowTrue,
    .dutyCyclePercent = 0
}
};

void SCTimer_0_init(void)
{
SCTIMER_Init(SCTIMER_0_PERIPHERAL, &SCTimer_0_initConfig);
// OUT_0, 2 events
SCTIMER_SetupPwm(SCTIMER_0_PERIPHERAL, &SCTimer_0_pwmSignalsConfig[0], kSCTIMER_EdgeAlignedPwm, DEF_M_FRQ, SCTIMER_0_CLOCK_FREQ, &SCTimer_0_pwmEvent[0]);
SCTIMER_CreateAndScheduleEvent(SCTIMER_0_PERIPHERAL, kSCTIMER_MatchEventOnly, 6000, kSCTIMER_Out_0, kSCTIMER_Counter_L, &SCTimer_0_event[0]);
SCTIMER_SetupOutputSetAction(SCTIMER_0_PERIPHERAL, kSCTIMER_Out_0, SCTimer_0_event[0]);
SCTIMER_CreateAndScheduleEvent(SCTIMER_0_PERIPHERAL, kSCTIMER_MatchEventOnly, 12000, kSCTIMER_Out_0, kSCTIMER_Counter_L, &SCTimer_0_event[5]);
SCTIMER_SetupOutputClearAction(SCTIMER_0_PERIPHERAL, kSCTIMER_Out_0, SCTimer_0_event[5]);
SCTIMER_IncreaseState(SCTIMER_0_PERIPHERAL);
// OUT_1, 4 events
SCTIMER_SetupPwm(SCTIMER_0_PERIPHERAL, &SCTimer_0_pwmSignalsConfig[1], kSCTIMER_EdgeAlignedPwm, DEF_M_FRQ, SCTIMER_0_CLOCK_FREQ, &SCTimer_0_pwmEvent[1]);
SCTIMER_ScheduleEvent(SCTIMER_0_PERIPHERAL, SCTimer_0_event[0]);
SCTIMER_CreateAndScheduleEvent(SCTIMER_0_PERIPHERAL, kSCTIMER_MatchEventOnly, 25, kSCTIMER_Out_0, kSCTIMER_Counter_L, &SCTimer_0_event[1]);
SCTIMER_SetupOutputSetAction(SCTIMER_0_PERIPHERAL, kSCTIMER_Out_1, SCTimer_0_event[1]);
SCTIMER_CreateAndScheduleEvent(SCTIMER_0_PERIPHERAL, kSCTIMER_MatchEventOnly, 5975, kSCTIMER_Out_0, kSCTIMER_Counter_L, &SCTimer_0_event[2]);
SCTIMER_SetupOutputClearAction(SCTIMER_0_PERIPHERAL, kSCTIMER_Out_1, SCTimer_0_event[2]);
SCTIMER_CreateAndScheduleEvent(SCTIMER_0_PERIPHERAL, kSCTIMER_MatchEventOnly, 6025, kSCTIMER_Out_0, kSCTIMER_Counter_L, &SCTimer_0_event[3]);
SCTIMER_SetupOutputSetAction(SCTIMER_0_PERIPHERAL, kSCTIMER_Out_1, SCTimer_0_event[3]);
SCTIMER_CreateAndScheduleEvent(SCTIMER_0_PERIPHERAL, kSCTIMER_MatchEventOnly, 11975, kSCTIMER_Out_0, kSCTIMER_Counter_L, &SCTimer_0_event[4]);
SCTIMER_SetupOutputClearAction(SCTIMER_0_PERIPHERAL, kSCTIMER_Out_1, SCTimer_0_event[4]);
}

Re: LPC845 SCTimer/PWM

Omar_Anguiano — Thu, 12 Sep 2019 20:53:35 GMT

Hello Владимир Орлов

Yes, each PWM allocates 2 events, one for the pulse period and the other for the frequency. To set multiple events you can use SCTIMER_CreateAndScheduleEvent() function.

Also I suggest you to take a look to this document SCTimer/PWM cookbook. This contains a collection of examples and usage notes for the SCTimer/PWM block.

Let me know if this is helpful.

Best regards,

Omar

Re: LPC845 SCTimer/PWM

keyzet_89 — Fri, 13 Sep 2019 06:46:54 GMT

Good afternoon, Omar.
Thanks for your reply. Yes, this document is very useful. But the question still remained. This document on pages 14-15 has an example of Simple PWM. Can I change it to fit my task in this way?

void SCT_Init(void)
{
    LPC_SCT->CONFIG        |= (1 << 17);                // two 16-bit timers, auto limit
    LPC_SCT->CTRL_L        |= (12-1) << 5;              // set prescaler, SCTimer/PWM clock = 1 MHz

    LPC_SCT->MATCHREL[0].L = 10-1;                     // match 0 @ 10/1MHz = 10 usec (100 kHz PWM freq)
    LPC_SCT->MATCHREL[1].L = 4;                        // match 1 used for duty cycle (in 10 steps)
   LPC_SCT->MATCHREL[2].L = 6;                        // match 2 used for duty cycle (in 10 steps)
   LPC_SCT->MATCHREL[3].L = 8;                        // match 3 used for duty cycle (in 10 steps)

    LPC_SCT->EVENT[0].STATE = 0xFFFFFFFF;               // event 0 happens in all states
    LPC_SCT->EVENT[0].CTRL = (1 << 12);                // match 0 condition only

    LPC_SCT->EVENT[1].STATE = 0xFFFFFFFF;               // event 1 happens in all states
    LPC_SCT->EVENT[1].CTRL = (1 << 0) | (1 << 12);     // match 1 condition only

   LPC_SCT->EVENT[2].STATE = 0xFFFFFFFF;               // event 1 happens in all states
    LPC_SCT->EVENT[2].CTRL = (2) | (1 << 12);          // match 1 condition only / event 2 associate with match 2

   LPC_SCT->EVENT[3].STATE = 0xFFFFFFFF;               // event 1 happens in all states
    LPC_SCT->EVENT[3].CTRL = (3) | (1 << 12);          // match 1 condition only / event 3 associate with match 3

    LPC_SCT->OUT[0].SET     = (1 << 0) | (1 << 2);                 // event 0 and event 2 will set   SCTx_OUT0
    LPC_SCT->OUT[0].CLR     = (1 << 1) | (1 << 3);                 // event 1 and event 3 will clear SCTx_OUT0

    LPC_SCT->CTRL_L        &= ~(1 << 2);                // unhalt it by clearing bit 2 of CTRL reg
}

Will this work as intended?

Best regards, Владимир.

Re: LPC845 SCTimer/PWM

Omar_Anguiano — Tue, 17 Sep 2019 17:59:57 GMT

Hello Владимир Орлов

Can you tell me what are intended to do? With the information I have I'm not able to tell you if it works, I would need to put me on your application context.

Best regards,

Omar

Re: LPC845 SCTimer/PWM

keyzet_89 — Thu, 19 Sep 2019 07:14:54 GMT

Good afternoon, Omar.
In fact, I need to get something like this output signal. Two outputs, the frequency is 2 times different and there is a phase shift. The severity is different. Thus, output_1 is obtained as in the example with Simple PWM. However, output_0 will have 4 events - 2 on SET and 2 on CLR. The total number of events 8 does not exceed. After re-reading the user manual, I did not find in it restrictions on the number of events per output.
Sorry for such a weird schedule. The brown dotted line is the beginning of the counter.

Best regards, Владимир.

Re: LPC845 SCTimer/PWM

Omar_Anguiano — Mon, 23 Sep 2019 20:02:16 GMT

Hello Владимир Орлов.

I agree with you, the number of events needed for your application does not exceed the permitted one. I suggest to check this example as a guide to design your application "max_sctimer_multi_state_pwm". This example can be found at the sdk.

On the example focus on the function SCTIMER_SetupPwm(). This function configures the PWM parameters and sets 2 events with SCTIMER_CreateAndScheduleEvent()

Use this function as reference to design your function for the PWM of your OUT_0. Add the events with SCTIMER_CreateAndScheduleEvent()

You may find a more detailed explanation of each function at the example driver.

Let me know if this is helpful

Best regards,

Omar