i2c driver from scratch using direct register access

RE: i2c driver from scratch using direct register access

vikrant8051 — Fri, 15 Dec 2017 15:21:44 GMT

[issue is solved !!]

I found my mistake. Here I'm presenting my ( tested on nRF52840-PDK ) corrected version .....

//-----------------------------------------------------------------------------------------------------------

void i2c_init(unsigned char addr)
{ 

    NRF_TWI0->PSELSCL=27;
    NRF_TWI0->PSELSDA=26;

    NRF_TWI0->ADDRESS=addr;

    //TWSR = 0x00;
    //NRF_TWI0->FREQUENCY = 0x01980000;   //100 KHz 
    NRF_TWI0->FREQUENCY = 0x06680000;     //400 Khz

    NRF_TWI0->ENABLE = 0x00000005;
}


void i2c_startTX() 
{ 
    NRF_TWI0->TASKS_STARTTX=1; 
}


void i2c_startRX() 
{ 
    NRF_TWI0->TASKS_STARTRX=1;
}

void i2c_write(unsigned char data)
{ 
    NRF_TWI0->TXD=data;
    while(NRF_TWI0->EVENTS_TXDSENT==0){}
    NRF_TWI0->EVENTS_TXDSENT=0;
}

unsigned char i2c_read(unsigned char nack)
{

    unsigned char data;
    
    if(nack==1)
    {
        NRF_TWI0->TASKS_STOP=1;
    }

    while(NRF_TWI0->EVENTS_RXDREADY==0){}  
    NRF_TWI0->EVENTS_RXDREADY=0;

    data = NRF_TWI0->RXD;

    return data;

}


void i2c_stopTX(void)
{
    NRF_TWI0->TASKS_STOP=1;
    while(NRF_TWI0->EVENTS_STOPPED==0){}
    NRF_TWI0->EVENTS_STOPPED=0;
}

void i2c_stopRX(void)
{
    while(NRF_TWI0->EVENTS_STOPPED==0){}
    NRF_TWI0->EVENTS_STOPPED=0;
}

//--------------------------------------------------------------------------------------------------------


void eeprom_init()
{
    unsigned char cntr;

    i2c_init(0x50);  // EEPROM i2c address

    i2c_startTX();
    i2c_write(0x00);

    for(cntr=0;cntr<=15;cntr++)
    {
        i2c_write('A' + cntr);
    }

    i2c_stopTX();

    nrf_delay_ms(10);  // delay for EEPROM write 

    serial_write_string("EEPROM initialisation completed !!\n\r");
}

void eeprom_read(unsigned char addr)
{
    unsigned char boo[17]={'\0'};
    unsigned char cntr;
    int data;

    i2c_startTX();
    i2c_write(addr);
    //i2c_stop();

    i2c_startRX();
    for(cntr=0;cntr<=15;cntr++)
    {
        if(cntr != 15)
        {
            boo[cntr]=i2c_read(0);
        }
        else
        {
            boo[cntr]=i2c_read(1);
        }
    }
    i2c_stopRX();

    serial_write_string(boo);    
    serial_write_string("\n\r");

}

//--------------------------------------------------------------------------------------------------------

RE: i2c driver from scratch using direct register access

vikrant8051 — Fri, 15 Dec 2017 15:04:25 GMT

Hey Jorgen Thanks for you clarification, I found my mistake.

The TWI master read sequence is stopped by triggering the STOP task. This task must be triggered before the last byte is extracted from RXD to ensure that the TWI master sends a NACK back to the slave before generating the stop condition.

I've not implemented this properly

RE: i2c driver from scratch using direct register access

Jørgen Holmefjord — Fri, 15 Dec 2017 13:23:07 GMT

Please have a look at the Master write sequence and Master read sequence documentation in the nRF52840 Objective Product Specifications.

RE: i2c driver from scratch using direct register access

vikrant8051 — Fri, 15 Dec 2017 13:01:10 GMT

serial_write_string() has no issue.

I want to only know, how nrf52840 send ACk or NACK in background ?

Actually what to send out of ACK or NACK, should be in control of developer !!

RE: i2c driver from scratch using direct register access

Jørgen Holmefjord — Fri, 15 Dec 2017 12:46:27 GMT

What is in your serial_write_string() function? Have you debugged the application to see how boo array is updated?

RE: i2c driver from scratch using direct register access

endnode — Fri, 15 Dec 2017 10:56:45 GMT

These while {} busy loops are soooooo ugly! Why you don't do proper wait for event/interrupt and interrupt handler to catch I2C events?