PWM¶

Note

The Datasheet specifies PWM channels 0 and 1. The Raspberry Pi has pins for PWM channels 1 and 2, you just need to add one.

Macros¶

RNG_CHANNEL0¶

DAT_CHANNEL0¶

RNG_CHANNEL1¶

DAT_CHANNEL1¶

#define RNG_CHANNEL0    PWM->RNG1
#define DAT_CHANNEL0    PWM->DAT1
#define RNG_CHANNEL1    PWM->RNG2
#define DAT_CHANNEL1    PWM->DAT2

To prevent confusion (because the Datasheet calls the PWM channels 1 and 2 and the Raspberry Pi 0 and 1) the values of the registers which need to be used “on the fly” are :code;`defined` from 2 to 1 and from 1 to 0.

Registers¶

struct pwm_register_map¶

This struct maps the registers of the PWM. The names of the struct members correspond to the registers from the Datasheet:

struct pwm_register_map {
    uint32_t CTL;
    uint32_t STA;
    uint32_t DMAC;
    uint32_t: 32;
    uint32_t RNG1;
    uint32_t DAT1;
    uint32_t FIF1;
    uint32_t: 32;
    uint32_t RNG2;
    uint32_t DAT2;
};

extern volatile struct pwm_register_map *PWM¶

PWM = (volatile struct pwm_register_map *)pwm_base_ptr;

By using this variable, the registers of the PWM can be accessed like this PWM->RNG1.

Enums¶

PWM channel number¶

This enum holds the values distinguishing PWM channel 0 and 1:
enum {
    PWM_CHANNEL0, PWM_CHANNEL1
};

Structs¶

pwm_channel_config¶

This struct is used to configure a PWM channel:

typedef struct {
    union {
        struct {
            uint32_t: 1;
            uint32_t mode: 1;
            uint32_t rptl: 1;
            uint32_t sbit: 1;
            uint32_t pola: 1;
            uint32_t usef: 1;
            uint32_t: 1;
            uint32_t msen: 1;
        };
        uint32_t ctl_register;
    };
    unsigned int divisor;
    uint32_t range;
} pwm_channel_config;

uint32_t ctl_register¶: This member can be directly edited by the anonymous struct inside this union. This register maps directly to the CTL register, with some offset for PWM 1. The settings of this register are described in the Macros.

unsigned int divisor¶: The divisor which is passed to the Clock Manager.

uint32_t range¶: The range to which the PWM counter counts before it starts over.

Functions¶

int pwm_map(void)¶: This function maps the PWM registers. It calls peripheral_map() with the values PWM_OFFSET and PWM_SIZE. On error -1 is returned.

void pwm_unmap(void)¶: This function unmaps the PWM registers.

void pwm_configure(int channel, pwm_channel_config *config)¶: This function configures channel with a pwm_channel_config pointed to by config.

void pwm_enable(int channel)¶: This function enables channel.

void pwm_disable(int channel)¶: This function disables channnel.

Configuration Values¶

`PWM_CTL_MODE_PWM`	Use PWM mode
`PWM_CTL_MODE_SERIALISER`	Use serialiser mode
`PWM_RPTL_STOP`	If serialiser mode: Transmission stops when fifo empty
`PWM_RPTL_REPEAT`	If serialiser mode: Repeat last data when fifo empty
`PWM_SBIT_LOW`	Output low when no transmission active
`PWM_SBIT_HIGH`	Output high when no transmission active
`PWM_POLA_DEFAULT`	Polarity is default
`PWM_POLA_INVERTED`	Polarity is innverted
`PWM_USEF_DATA`	Data register is transmitted
`PWM_USEF_FIFO`	Data from fifo is transmitted
`PWM_MSEN_PWMALGORITHM`	Use PWM algorithm
`PWM_MSEN_MSRATIO`	Use MS ratio