ADV7480 i2c issue

Hi,

 Please ensure, for read back after writing the register address you need to do another I2C start command to read the byte back.  Check out the Read and Write Sequence figure in the user manual.

Note:  Start condition - write operation (sub address) - Start condition - Read operation (data) - Stop condition
            Need to send STOP bit  when the whole process reading is done.To terminate a read/write sequence a stop signal must be sent. 

Please make sure with below things.

1. Do you have a pull-up or pull-down on the ADV7480 ALSB pin?

2. Do you have the pad on the bottom of the ADV7480 package connected well to GND?

Thanks,

Poornima

Hi Poornima,

Thank you for your reply.

Maybe you don't understand what I mean, 

PoornimaSubramani said:

1. Do you have a pull-up or pull-down on the ADV7480 ALSB pin?

The i2C communicates successfully for the first time, and I'm sure that the ALSB pin is pull-down.

The problem is why second and subsequent i2c communication failed,  why there is no ack when slave send data ,

There is an ACK when sending the slave address,  Is the slave busy or didn't receive the address ?

PoornimaSubramani said:

2. Do you have the pad on the bottom of the ADV7480 package connected well to GND?

I will ask hardware engineer to help confirm this question

Thank you!
Best regards.

Here is the waveform

thanks

Here is the waveform

thanks

Hi,

 1. There might be an chance of protocol problem with the host(I2C Master).  Please ensure on that.

 2. Please make sure the pad underneath the ADV7480 has good connection to GND? Several people have had trouble with this.

 3. Also check whether  I2C software routines expect 7-bit addresses or 8-bit addresses?

 4. Ensure the Reset and Power-down pins are controlled during I2C communication ?

 5. You can get the code from here:  It can be implemented on any micro.

      http://www.analog.com/en/circuits-from-the-lab/cn0282/vc.html

You can find code on the above website - under "Design & Integration Files"

Thanks,

Poornima

Hi，

 We bringup adv7480 on Samsung platform, I'm not sure if it is the problem of i2c master.

PoornimaSubramani said:

 2. Please make sure the pad underneath the ADV7480 has good connection to GND? Several people have had trouble with this.

pad underneath the ADV7480 has good connection to GND

I2C software routines expect 7-bit addresses and Reset and Power-down pins are controlled

now i am doubt the restart signal is right or not

Thank you!
Best regards.

Hi,

Please note, After the Start condition the master can generate a repeated Start. This is equivalent to a normal Start and is usually followed by the slave I2C address,

 

SDA - A high to low transition of SDA is considered as START and low to high transistion is considered as STOP

SCL - Both start & stop conditions SCL has to be high.

Please refer below snap for restart signal and compare accordingly with your waveform.

Also refer this FAQ https://ez.analog.com/video/w/documents/14315/i2c-read-and-write-sequence

Thanks,

Poornima

Hi,

So adv7480 's waveform is repeated start ,  not  stop & start like the illustration shown above？

Thank you!
Best regards.

Hi,

So adv7480 's waveform is repeated start ,  not  stop & start like the illustration shown above？

        When seeing the below ADV7480 waveform and its seems like the waveform is same like normal start & stop.

 Please refer below expert comment for repeat start ,

    "Reading back is a 2 step process. First you write the index register address you want to read back from and then send another Start bit, slave read address and then read back the data. The second Start is sometimes referred to as a repeat start".

Thanks,

Poornima