TWI starting

[rago]

Hello guys I tried to start TWI bus and got a lot of questions. (NRF51 1422 AC)

I added necessary libraries, could You tell me what more i need to include in my code :

    #define TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER (0U)
#define TWI_MASTER_CONFIG_DATA_PIN_NUMBER (2U)
//
static const nrf_drv_twi_t m_twi = NRF_DRV_TWI_INSTANCE(0);
static nrf_drv_twi_config_t nrf_drv_twi_config =
{	.scl = TWI_MASTER_CONFIG_CLOCK_PIN_NUMBER,
	.sda = TWI_MASTER_CONFIG_DATA_PIN_NUMBER,
	.frequency = NRF_TWI_FREQ_100K,
	.interrupt_priority = 0};

 void nrf_drv_twi_initialize(void){
	 
 nrf_drv_twi_init(&m_twi, &nrf_drv_twi_config, 0, NULL);
	nrf_drv_twi_enable(&m_twi);
	 
 }
 
 void nrf_drv_twi_uninitialize(void){
	 
	nrf_drv_twi_uninit(&m_twi);
	nrf_drv_twi_disable(&m_twi);
	 
 } 

and

nrf_drv_twi_tx(&m_twi,(0x49<<1),&read_adress,1,true);

nrf_drv_twi_rx(&m_twi,(0x49<<1),&value1, 1);

But is not working for me. Could u answer me too, operation (0x49<<1) with sensor adress is necessary with our example ?

[rago]

Thank You very much for answer ! I know Keil IDE, debugger is primary tool for me. Anyway, could You explain me three more questions ?

1st : While I'm sure with my code, using event hander in trasmission is necessary ?

2nd : I know first frame of transmission is :

(Adr)(Adr)(Adr)(Adr)(Adr)(Adr)(Adr)(R/W) where Adr are bytes of device adress

In sdk is written :

* @param[in] address    Address of a specific slave device **(only 7 LSB).**

How to understand it ?

In datasheet i have adress like 00110101x where last bit is not important.

But input param need 7 LSB with adress then if I impart paramter with adress i must make it like this :

x00110101

Where x is R/W bit ? In Twi_sensor example we have

#define MMA7660_ADDR        (0x98U >> 1)

What is compatible with my idea.

3rd : I checked lines using a oscilloscope, they looks good. I tried example from this topic : devzone.nordicsemi.com/.../

Is this solution correct ?

[MartinBL]

1. If you use an event handler you are able to see what errors might occur and respond to these. If you don't use an error handler and something goes wrong on your TWI bus you will end up in an endless loop. Your application will not work and you have no way of figuring out what is wrong.

2. If the address is given as 00110101x in the datasheet then I would assume that your device address is actually 00110101 (0x35). The x represents the R/W bit and is not really a part of the address. So in this case you should pass 0x35 as the address to nrf_drv_twi_tx(). Here is some example code that you can use to find your device's address and debug your application.

EDIT: Forgot to link to the examples.