Hi everyone,
I was just going through the library functions provided here in this link : nordic functions twi
But inside all these functions ,there is this parameter which is a pointer to a structure of this format :
| NRF_TWI_Type * | p_reg |
Can anyone tell me where i can find the elements that needs to be stored inside this structure ? or give me any idea on how to declare and define this structure?
Thanks!
Rajat
Hi,
NRF_TWI_Type * is a pointer to a structure with TWI registers. If you are using nRF52832 you will find the definition of the structure in a file called nrf52.h. This is what the structure looks like in SDK 15:
/**
* @brief I2C compatible Two-Wire Interface 0 (TWI)
*/
typedef struct { /*!< TWI Structure */
__O uint32_t TASKS_STARTRX; /*!< Start TWI receive sequence */
__I uint32_t RESERVED0;
__O uint32_t TASKS_STARTTX; /*!< Start TWI transmit sequence */
__I uint32_t RESERVED1[2];
__O uint32_t TASKS_STOP; /*!< Stop TWI transaction */
__I uint32_t RESERVED2;
__O uint32_t TASKS_SUSPEND; /*!< Suspend TWI transaction */
__O uint32_t TASKS_RESUME; /*!< Resume TWI transaction */
__I uint32_t RESERVED3[56];
__IO uint32_t EVENTS_STOPPED; /*!< TWI stopped */
__IO uint32_t EVENTS_RXDREADY; /*!< TWI RXD byte received */
__I uint32_t RESERVED4[4];
__IO uint32_t EVENTS_TXDSENT; /*!< TWI TXD byte sent */
__I uint32_t RESERVED5;
__IO uint32_t EVENTS_ERROR; /*!< TWI error */
__I uint32_t RESERVED6[4];
__IO uint32_t EVENTS_BB; /*!< TWI byte boundary, generated before each byte that is sent or
received */
__I uint32_t RESERVED7[3];
__IO uint32_t EVENTS_SUSPENDED; /*!< TWI entered the suspended state */
__I uint32_t RESERVED8[45];
__IO uint32_t SHORTS; /*!< Shortcut register */
__I uint32_t RESERVED9[64];
__IO uint32_t INTENSET; /*!< Enable interrupt */
__IO uint32_t INTENCLR; /*!< Disable interrupt */
__I uint32_t RESERVED10[110];
__IO uint32_t ERRORSRC; /*!< Error source */
__I uint32_t RESERVED11[14];
__IO uint32_t ENABLE; /*!< Enable TWI */
__I uint32_t RESERVED12;
__IO uint32_t PSELSCL; /*!< Pin select for SCL */
__IO uint32_t PSELSDA; /*!< Pin select for SDA */
__I uint32_t RESERVED13[2];
__I uint32_t RXD; /*!< RXD register */
__IO uint32_t TXD; /*!< TXD register */
__I uint32_t RESERVED14;
__IO uint32_t FREQUENCY; /*!< TWI frequency */
__I uint32_t RESERVED15[24];
__IO uint32_t ADDRESS; /*!< Address used in the TWI transfer */
} NRF_TWI_Type;
You can see how it lines up the actual TWI peripheral registers.
Thanks a lot!
Can you please tell me how to set the pin number?
can we write directly like scl=11;
sda=13;
and use them inside the function to set the pins?
or we need to proceed in some other way?
I suggest that you use the TWI drivers in the SDK and follow the documentation as well as having a look at the simple TWI examples, like the TWI Scanner example, to see how it can be configured. In this example the TWI pins are configured like this:
void twi_init (void)
{
ret_code_t err_code;
const nrf_drv_twi_config_t twi_config = {
.scl = scl_pin,
.sda = sda_pin,
.frequency = NRF_DRV_TWI_FREQ_100K,
.interrupt_priority = APP_IRQ_PRIORITY_HIGH,
.clear_bus_init = false
};
err_code = nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
APP_ERROR_CHECK(err_code);
nrf_drv_twi_enable(&m_twi);
}I suggest that you use the TWI drivers in the SDK and follow the documentation as well as having a look at the simple TWI examples, like the TWI Scanner example, to see how it can be configured. In this example the TWI pins are configured like this:
void twi_init (void)
{
ret_code_t err_code;
const nrf_drv_twi_config_t twi_config = {
.scl = scl_pin,
.sda = sda_pin,
.frequency = NRF_DRV_TWI_FREQ_100K,
.interrupt_priority = APP_IRQ_PRIORITY_HIGH,
.clear_bus_init = false
};
err_code = nrf_drv_twi_init(&m_twi, &twi_config, NULL, NULL);
APP_ERROR_CHECK(err_code);
nrf_drv_twi_enable(&m_twi);
}