NRF9160-SICA-R7 datasheet(166/400 Pages) NORDIC

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Peripherals

Note that registers SEQ[n].REFRESH and SEQ[n].ENDDELAY are ignored when DECODER.MODE=NextStep.

The next value is loaded upon every received NEXTSTEP task.

SEQ[n].PTR is the pointer used to fetch COMPARE values from RAM. If the SEQ[n].PTR is not pointing to

a RAM region, an EasyDMA transfer may result in a HardFault or RAM corruption. See Memory on page

21 for more information about the different memory regions. After the SEQ[n].PTR is set to the desired

RAM location, the SEQ[n].CNT register must be set to the number of 16-bit half words in the sequence. It

is important to observe that the Grouped mode requires one half word per group, while the Single mode

requires one half word per channel, thus increasing the RAM size occupation. If PWM generation is not

running when the SEQSTART[n] task is triggered, the task will load the first value from RAM and then start

the PWM generation. A SEQSTARTED[n] event is generated as soon as the EasyDMA has read the first

PWM parameter from RAM and the wave counter has started executing it. When LOOP.CNT=0, sequence

n=0 or 1 is played back once. After the last value in the sequence has been loaded and started executing,

a SEQEND[n] event is generated. The PWM generation will then continue with the last loaded value. The

following figure illustrates an example of a simple playback.

COMPARE

SEQ[0].PTR

COMPARE

PWM pulse period

COMPARE

SEQEND[0]

SEQSTARTED[0]

SEQSTART[0]

Event/Tasks

Continues with last setting

Figure 46: Simple sequence example

The following source code is used for configuration and timing details in a sequence where only sequence

0 is used and only run once with a new PWM duty cycle for each period.

NRF_PWM0->PSEL.OUT[0] = (first_pin << PWM_PSEL_OUT_PIN_Pos) |

(PWM_PSEL_OUT_CONNECT_Connected <<

PWM_PSEL_OUT_CONNECT_Pos);

NRF_PWM0->ENABLE

= (PWM_ENABLE_ENABLE_Enabled << PWM_ENABLE_ENABLE_Pos);

NRF_PWM0->MODE

= (PWM_MODE_UPDOWN_Up << PWM_MODE_UPDOWN_Pos);

NRF_PWM0->PRESCALER

= (PWM_PRESCALER_PRESCALER_DIV_1 <<

PWM_PRESCALER_PRESCALER_Pos);

NRF_PWM0->COUNTERTOP = (16000 << PWM_COUNTERTOP_COUNTERTOP_Pos); //1 msec

NRF_PWM0->LOOP

= (PWM_LOOP_CNT_Disabled << PWM_LOOP_CNT_Pos);

NRF_PWM0->DECODER

= (PWM_DECODER_LOAD_Common << PWM_DECODER_LOAD_Pos) |

(PWM_DECODER_MODE_RefreshCount << PWM_DECODER_MODE_Pos);

NRF_PWM0->SEQ[0].PTR = ((uint32_t)(seq0_ram) << PWM_SEQ_PTR_PTR_Pos);

NRF_PWM0->SEQ[0].CNT = ((sizeof(seq0_ram) / sizeof(uint16_t)) <<

PWM_SEQ_CNT_CNT_Pos);

NRF_PWM0->SEQ[0].REFRESH = 0;

NRF_PWM0->SEQ[0].ENDDELAY = 0;

NRF_PWM0->TASKS_SEQSTART[0] = 1;

To completely stop the PWM generation and force the associated pins to a defined state, a STOP task can

be triggered at any time. A STOPPED event is generated when the PWM generation has stopped at the end

of the currently running PWM period, and the pins go into their idle state as defined in GPIO OUT register.

4418_1315 v2.0

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NRF9160-SICA-R7 Datasheet(PDF) 166 Page - Nordic Semiconductor

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