RE: i2c/twi detup on register level

luke — Wed, 25 Jan 2017 09:42:55 GMT

thank u so much for ur help!

RE: i2c/twi detup on register level

Stian Røed Hafskjold — Wed, 23 Nov 2016 14:00:36 GMT

This line,

NRF_TWIM0->SHORTS = 0x00001780;

enables all shorts. Enable only one of them, like LASTTX_STOP. Which sets the stop signal after last byte has been transferred.

Here you enable interrupt on all events:

NRF_TWIM0->INTEN = 0x019C0022;

Enable only the ones you need. In your example above, you don't use interrupts at all, so you should set this register to 0.

This line,

NRF_TWIM0->ERRORSRC = 0x00000006;

is only used for checking the error source when an error is encountered. Do not write to this register.

You must write 1 to TASKS_STARTTX like this:

NRF_TWIM0->TASKS_STARTTX = 1;

MyArrayList must be static so that the pointer is valid after the function returns. Something like this should work:

#define BUFFER_SIZE 2
#define TWI_SCL 13
#define TWI_SDA 14
typedef struct ArrayList
{
    uint8_t buffer[BUFFER_SIZE];
} ArrayList_type;

static ArrayList_type tx_buf[2];
static ArrayList_type * tx_buf_p = tx_buf;

void initI2c()
{
    NRF_GPIO->PIN_CNF[TWI_SCL] = (6 << 8) | (3 << 2); //configure pins with pullup
    NRF_GPIO->PIN_CNF[TWI_SDA] = (6 << 8) | (3 << 2);
    NRF_TWIM0->SHORTS = (1 << 9);     //LASTTX_STOP
    NRF_TWIM0->PSEL.SCL = TWI_SCL;
    NRF_TWIM0->PSEL.SDA = TWI_SDA;
    NRF_TWIM0->FREQUENCY = 0x06400000;  //400kbps
    NRF_TWIM0->ADDRESS = 0x0000078;
    NRF_TWIM0->ENABLE = 6;
}

void WriteTwiCommand (uint8_t * Data)
{
    // copy data to TX buffer:
    for(int i = 0; i < BUFFER_SIZE; i++){
        tx_buf[0].buffer[i] = Data[i];
    }
    NRF_TWIM0->TXD.MAXCNT = BUFFER_SIZE;
    NRF_TWIM0->TXD.LIST = 1;
    NRF_TWIM0->TXD.PTR = (uint32_t)tx_buf_p; //typecast pointer to uint32_t to get rid of warning.
    NRF_TWIM0->TASKS_STARTTX = 1;
}
int main(void)
{
    initI2c();
    uint8_t data[BUFFER_SIZE] = {1,2}; // data you want to transmit
    WriteTwiCommand(data);
    while (true)
    {
        __WFE(); // CPU to sleep
    }
}

Anyways, why do you want to write directly to the registers like this? You should use the hardware driver in the SDK, it will save you a lot of trouble.