continuous data about example twi_master_using_app_twi

[Yoojin.Jang]

hello. I want use I2C program. so, I used twi_master_using_app_twi example. SDA is output only 1byte(0x21). I need to output a continuous 5byte. Where do I need to modify the part. thank you.

[Jorge]

your length is set to what number? you get the first or the last byte?

[Yoojin.Jang]

#define DATA_ARRAY_LEN 10 uint8_t data[DATA_ARRAY_LEN] = {0x40, 0xC0, 0x01, 0x02, 0x01, 0x02, 0x01, 0x02, 0x01, 0x88}; #define MMA7660_ADDR (0x98U >> 1)

    err_code = nrf_drv_twi_tx(&m_twi_mma_7660, MMA7660_ADDR, data, DATA_ARRAY_LEN, true);
    			APP_ERROR_CHECK(err_code);

I get one byte is link address as below. blog.naver.com/.../220723715390 SCLK is 9byte. is it right? please confirm it.

[MartinBL]

Hi,

On the image in your comment you are sending a 7 bit address (0x98 >> 1) with a write bit. You also get a Not Acknowledge (NACK) bit in the end. The 9th bit on the SCK is for the NACK bit.

Read about NACK and addresses in the I2C spec here: I2C Bus Specification. Read about the difference between 8 and 7 bits addresses and why you right shift some addresses here.

The NACK you get is important to note. It signifies that you are trying to transfer a byte, but no slave is responding. This is often due to one of the following reasons:

• You use the wrong slave address.
• You use wrong pins on your slave and/or the nRF5. Given that can provide logic trace you obviously know what pins on the nRF5 is used for TWI, but double check that SCK on the nRF5 is connected to SCK on the slave and likewise for SDA.
• Your slave is not powered on.
• The nRF5 has internal pull-ups, but you might need to add external ones as well. Your logic trace looks good though, so this is probably not an issue.

[Yoojin.Jang]

thank you for your support. I want master communication. so, set 0x98>>1 with a write bit. I wrong master address? SCK and SDA pin is right.

[MartinBL]

You need 8 bits to write 0x98 (b1001 1000) and the drivers expect a 7 bit address. Hence we can definitely say that you need to right shift the address 1 bit as you do. The drivers will take care of assembling the 7 bit address and the R/W bit. This means that as far as I can see you are doing everything right with regards to the address and R/W bit. What kind of slave do you use? What is the part number? Are you sure it has power?