LAUNCHXL-F28379D: No reading obtained when interfacing F28379D with a BiSS encoder without Position Manager BOOTXL.

Please check that dataReady and your counter are both defined as volatile. 

Thanks for the reply, Lori. I defined both the BISSC_DATA_STRUCT struct and the counter as volatile, but still could not see them changed during running.

Are you using the hardware from TI? (BOOSTXL_POSMGR) or your own hardware? 

I suggest checking some of the signals using a oscilloscope:

Do you see the clock at the SPICLK pin?

Is the MA line active as expected?

Is a response seen from the encoder on SL?

Note: I will be out of the office next week so additional responses will be delayed until ~Oct 23rd

Thanks, Lori. I am not using BOOSTXL_POSMGR, I just simply connect the encoder to a F28379D launchxl pad. wiring scheme follows the figure below.

the encoder data sheet can be found in the following link(https://www.rls.si/eng/fileuploader/download/download/?d=1&file=custom%2Fupload%2FMBAD01_10_bookmark.pdf)

Some updates about what I found:

When I powered the encoder using the launchpad, interrupt was not triggered

    1. BiSS clk signal is a square wave with a max of 4.3V and a min of 4.1V

    2. SPI CLK signal is always high and at 3.3V

    3. SPI SIMO signal is always high and at 3.3V

However, When I powered the encoder using an external 5V power supply, the interrupt worked

    1. BiSS CLK signal is normal and at a range of 0~3.3V

    2. SPI CLK signal is normal and at a range of 0~3.3V

    3. SPI SIMO signal is abnormal and always high of 3.3V

I would greatly appreciate if you could provide me some hints to resolve these abnormal phenomena!

Hello Sichuan,

Lori is presently out of office, and will return around Tuesday of next week. She'll be able to look at your question at that time.

Thank you,

Jason Osborn

Hello, I believe the GPIO numbers in that diagram are not all correct - check the setup_GPIO() function in the example. 

Thanks, Jason!

Thanks for the suggestions! I will definitely double check! Lori

Hello, Lori,

I just tried to change the GPIO number on my case, However. the problem is still there. Can I use the F28379D board to provide a 5V power supply for the encoder? or do I need to use an external power supply for the encoder?

Although I used an external power supply to power the encoder, the reading always has crc_incorrect problem. I believe this is because the SLO data is not correctly collected. 

Yes, you can power the encoder externally. I would make sure ground connections are common with the LaunchPad. If you are not using the BOOSTXL_POSMGR, do you have your own board with RS-485 drivers?

It would also be good to re-check the signals now that you have changed the GPIOs being used. 

Correct, F2837xD does not handle differential signals directly.   I will close this thread. 

Cheers

Lori