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  • TI Thinks Resolved

TLA2024: IIC communication failed

Prodigy 80 points

Replies: 4

Views: 227

Part Number: TLA2024

  Hi sir

I used msp430f2001 to control ATL2021, but found that IIC could not communicate. I observed the waveform through an oscilloscope and determined that the device returned a high level.However, there is no problem with my device address and waveform timing sequence. Could you help me analyze the cause of the problem?

I2C configuration is below.
Sleve Addr : 48h (ADDR Pin : GND)

 Vdd : 4.0V
 I2C BUS Pull-up Resistor : 2.4K Ohm

  • Hi,


    I'm not entirely sure what the problem is in the communication, but I'm not sure the I2C is correct. For I2C, each communication is 9 bits. There are 8 for data, and then an ACK bit by the master or slave. In the first scope shot that you show, there are the data bytes 48 for the address (7 bits) and then a 0 for a write (1 bit).

    However, after that, you have both SCL and SDA lines that are both briefly high. Normally there would be the ACK by the device as the 9th bit in this communication. Here you don't appear to have the same time added for the 9th byte. Alternately, the narrow SCL high pulse might be wide enough for a real bit (it's hard to tell from the scope shot), but there's no ACK from the slave.

    For the next test, I would make sure that there is the 9th bit for the ACK. If you continue to have problems, can you please post a scope shot that shows more of the I2C communication? This shows 1 full byte, and the next byte without the ACK. Next time, post a shot with the full four or five bytes of the I2C communication.


    Joseph Wu
  • In reply to Joseph Wu:

    Hi

    I followed your advice and extended the time of the ninth SCL high, however, the slave machine still did not ACK.

  • In reply to user5973110:

    Hi,


    At this point, I'm not sure what the problem is. The waveform looks correct now for the communication. If you have a schematic and a diagram of the connections to the master, are you able to post them? I would re-check all of the connections to make sure that they are correct.

    Also, check the GND connection from master to slave, make sure that there is common ground. Verify that the ADDR pin is properly connected to GND so that the device recognizes the correct I2C address. I'd also check the orientation of the TLA2024 just to make sure that it was installed correctly. I would use an ohmmeter to check all connections of supply, ground, SDA and SCL from source to destination. Check to see if there are any other shorted pins to the device.

    You might also consider checking the other addresses that the device might respond to, just in case there the ADDR pin is misconnected.

    I would also consider replacing the device. There might have been some damage from installing it on the board.


    Joseph Wu
  • In reply to Joseph Wu:

    Hi,


    I haven't heard from you for a week and I thought I'd check to see if you've solved the I2C communication problem. As I mentioned in the last post, the first part of the I2C communication looked like it was set up correctly. I also mentioned a few other things to check with your setup of the device in your test.

    I'll close this post for now, but if you have any further problems, post back and we can review the tests you've run for this device.


    Joseph Wu

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