LAUNCHXL-F280025C: Could not read one byte throught PMbus

Wang,

It is not clear from you message, which PMBus test failed. Did any of these test pass?

    // Quick command  : Slave address + R / W + STOP
    // Send  Byte     : RX Byte #0 + PEC + STOP
    // Write Byte     : RX cmd 0 + RX Byte #0 + PEC + STOP
    // Write Word     : RX cmd 0 + RX Byte #0 + RX Byte #1 + PEC + STOP
    // Ext.Write Byte : RX cmd 0 + RX cmd 1 + RX Byte #0 + PEC + STOP
    // Ext.Write Word : RX cmd 0 + RX cmd 1 + RX Byte #0 + RX Byte #1 + PEC + STOP
    // Ext.Read Byte  : RX cmd 0 + RX cmd 1 + RX Byte #0 + TX PEC + STOP
    // Ext.Read Word  : RX cmd 0 + RX cmd 1 + TX Byte #0 + TX Byte #1 + TX PEC + STOP

Regards,

Manoj

Dear Mohan

We have no problems on our test side.

Now our program is normal Main loop, ADC interrupts to start data collection first, ADC data collection is sent out through PmBUS.

We found that when the next ADC samples the data, it sends the data through PMbus. When the highest bit of the first 8bit data is 1, PMbus cannot send the data. We solved the problem by sending the first data &0x7F. But we want to understand why.

By the way, only  the cpu loading over 60%  this situation will happed ,it's too strange!

Wang, 

Request  you to clarify if  you are using "PMBus over I2C" or "PMBus" to send the data? 

Best Regards

Siddharth 

Dear Sidharth

It's "PMBus over I2C" .

Wang, 

Which PMBus command (WriteByte/WriteWord) are you using to send the data?  

Best Regards

Siddharth

Hi Siddhardth

We use the send one byte command .

And we sending a generated interrupt that continues sending data with the interrupt.

Wang, 

Will try to reproduce the issue with the standard TI example and get back to you.

Best Regards

Siddharth

Dear Siddharth

Very appricate if u have any update .

Wang,

Will update you about it by today.

Best Regards

Siddharth

Wang ,

I tried running the SendByte Command with data of 0xFF and was able to receive the same on the Slave. 

 To narrow down the issue, can you check the I2C Status register when you send data with highest bit of the data is one?

Best Regards

Siddharth