Why can not read twi data ? twi interfacing with RTC DS1307....

RE: Why can not read twi data ? twi interfacing with RTC DS1307....

chchoi — Thu, 12 Oct 2017 23:45:11 GMT

Thank you for your response , thank you very much!

RE: Why can not read twi data ? twi interfacing with RTC DS1307....

MartinBL — Thu, 12 Oct 2017 13:54:18 GMT

We don't have examples or code for that around here, but if you google something like "dS1307 c library" i'm sure you will find some tips.

RE: Why can not read twi data ? twi interfacing with RTC DS1307....

chchoi — Thu, 12 Oct 2017 07:57:56 GMT

I have finally read the data.

DS1337 Get Time. twi_i2c_read_err 0, 0 ,[00]

0 = 0x38
1 = 0x42
2 = 0x3A
3 = 0x88
4 = 0x23
5 = 0x47
6 = 0x17
7 = 0x70
8 = 0x7E
9 = 0xF7
10 = 0xE9
11 = 0x23
12 = 0xC1
13 = 0x78
14 = 0x67
15 = 0x37

The reason I could not read it was because I read sda scl using only battery power. I can read the data after connecting 3.2v power to VCC, GND in DS1307.

Thank you for your response. I would appreciate it if you could give me a place to refer to how to convert from buffer data to date and time data.

RE: Why can not read twi data ? twi interfacing with RTC DS1307....

MartinBL — Thu, 12 Oct 2017 07:02:30 GMT

Is xfer_completed declared volatile? THis could be important.

Can you post your entire code?

RE: Why can not read twi data ? twi interfacing with RTC DS1307....

chchoi — Thu, 12 Oct 2017 00:51:09 GMT

Thank you for your help.

I tried it but it did not work.

switch(p_event->type)
{
	case NRF_DRV_TWI_EVT_DONE:				

		if ( (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_RX) || (p_event->xfer_desc.type == NRF_DRV_TWI_XFER_TX))
		{
			xfer_completed = true;
			printf("\n\r twi_handler complete .\r\n");
		}		

		else
		{
			xfer_completed = false;
		}

		break;	

	default:
		break;
}

//	do
//   {
//       __WFE();
//  }while(xfer_completed == false);

err_code = nrf_drv_twi_rx(&m_twi_ds1307, DS1307_ADDR, r_buf, sizeof(r_buf));		
//	 xfer_completed = false;
nrf_delay_ms(10);

There was no effect if enough delay was given.

What are the elements I have not thought of yet?

RE: Why can not read twi data ? twi interfacing with RTC DS1307....

MartinBL — Wed, 11 Oct 2017 08:57:05 GMT

Hi.

Since you are using a TWI handler function, you are using the TWI driver in the so called "non-blocking" mode. That means that nrf_drv_twi_rx() returns immediately, but the TWI reading is actually not completed before later. So since you initiate r_buf[] to all zeros, and you haven't actually received any data yet when you call printf(), all you see is zeros.

You can easily solve this problem by using the driver in blocking mode, or use a flag in your TWI handler that and wait for that flag to be set before you read out your data.

In your post you don't show any code that tells the DS1307 what registers you want read either. I assume you have it in your application? Your code should look something like this:

err_code = nrf_drv_twi_tx(&m_twi_ds1307, DS1307_ADDR, address_that_you_want_to_read, 1);
APP_ERROR_CHECK(err_code);

// Use blocking mode or wait in a while(!tx_flag) loop here

uint8_t   r_buf[16]={0,};
err_code = nrf_drv_twi_rx(&m_twi_ds1307, DS1307_ADDR, r_buf, sizeof(r_buf));
APP_ERROR_CHECK(err_code);

// Use blocking mode or wait in a while(!rx_flag) loop here

for (uint32_t i = 0; i < 16; i++)
{
    printf("%d = 0x%02X \n",i, r_buf[i] );  
}

Also, make sure to try this example to confirm that you have wired everything correctly and use the right address.