BQ76PL455EVM: No UART response

Are you using our sample code or your own?

actual codes are available in TI product folder.

Hi Roger, I am using the sample code modified for the TMS570LS1224 (link above) since the original sample code was not working with my MCU.

Could you link me to the TI product folder? I may be looking at the wrong sample code.

Hi Xing,

Please make sure that the baud rate of the MCU is set to match the pl455 (should default to 250k baud). Please also make sure it is configured to work with only 1 stop bit.

Please also confirm that a wakeup pulse is being sent over, so that the pl455 is waking up.

I would recommend getting the MCU uart to work properly first with the expected pl455 settings, perhaps through using the loop back function. The team on the hercules (tms570) forum should be able to help you,

Hi David,

I have tried those and confirmed the wakeup pulse works. I also sent a command from the PC GUI to the EVM and got the expected reply, however when I loop send from the TMS I do not get any reply. This was checked with my logic analyzer.

PC: 81 00 0A 00 2E 9C sent and 00 00 00 00 received

TMS: only 81 00 0A 00 2E 9C  was sent

 

Yellow: EVM TX

Green: EVM RX

Red: Wake

 

I have noticed that the TMS will send a wake command when it sends the transmit signal.

Thanks,

XingLu

guess you have traced the problem!
No need to send WAKE every time Tx.

Hi Vish, I have realized that I have not been reading the WAKE pin directly on the board, which gives me an inverted signal. After correcting that, the signals look correct however I am still not getting any response. My code consists of the basic initialization followed by:


uint8 send[6] = {129, 0, 10, 0, 46, 156}; //81 00 0A 00 2E 9C

while(1){
WakePL455();
sciSend(sciREG, 6, send);

delayms(1000);
}

Hi Xing,

I noticed that you mentioned setting the baudrate of the pl455, but did not mention setting the baudrate of the TMS. Considering the issues you are having (wakeup working but communications not), it is likely that the baudrate of the TMS is not matching the baudrate of the pl455. If the TMS code you used does not update the microcontroller itself, you will run into issues similar to those you are seeing. For instance, in the example code, there are several places in which the baudrate of the microcontroller is updated, and each will need to be changed based on the baudrate you choose. This should fix the issues you are having.

Let us know if you have any additional issues or problems.

Regards,
Vince

Hi Vince,

In my pl455.h file I have found #define BAUDRATE 250000 which is the baudrate I want. However looking through other files such as the .c and .h files of sci and gio I could not find the baudrate setting of the MCU. Is there a file you can suggest where I could find the baud rate setting?

Also, I know that the WAKE pin activates when I use the logic analyzer directly on my EVM, but is there a way to verify that the EVM received it or is that the correct way?

Thanks,
XingLu

Hi Xing,

A great document for properly setting up UART on the TMS570LS1224 is SPNA124A (link: www.ti.com/.../spna124a.pdf). This covers all of the details on setting baudrate for the microcontroller, and will provide excellent help with other required setup functions for the microcontroller.

To give you a head-start though, here's some extra information:
In the default sample code for the PL455 and TMS570, there are several instances in which baudrate is changed.

Functions such as "sciSetBaudrate" will set the baudrate of the TMS570, while functions that change the baudrate using ReadReg/WriteReg will change the baudrate of the PL455. These are just two of the ways the baudrate is changed in the code.

As you are using code that has been modified for a different microcontroller, I would recommend that baud-rate setup is modified to match the microcontroller being used, as well as any other necessary settings as mentioned in the SPNA124A document.

Let me know if I can be of any further assistance!

Thanks,
Vince Toledo

Hi Vince,

I have checked through my code and made sure that the baudrate is set correctly. I am considering now that the values I am transmitting may be incorrect as the PL455 may not be set up to receive the specific command at the moment. Do you have any suggestions on any message I could transmit from the TMS570 that would prompt any response from the PL455?

Thanks,
XingLu Wang