MCU-PLUS-SDK-AM243X: BiSS Safety

A bit more details

I am able to communicate with above mentioned encoder using the normal non safety position.

My problem is on the safety data. I am not able to configure the BiSS controller to read safety data.

Thanks

Alan I

Alan

Can you share the steps you have tried for configuring the safety position?

Regards

Dhaval

Hi Dhaval

Renishaw BiSS Safety encoders  runs in safety mode by default where control word and safety word are available on power-up. No additional configuration is required on the encoder side. In fact we can't read or write to any register on this encoder.

Using BiSS diagnostis example. These are the steps that I took

1-  Specify No of Position Data Bits on startup  1st encoder single turn> 32

         Multiturn > 0

         Daisy Chain , 2nd encoder single turn > 0

2 - Execute command 3 | Encoder send position values 

      Encoder is able to return position with correct CRC

3- Since this encoder is by default in safety mode. I proceed to execute  command 7 , Enable Safety Mode > 1

4- Execute command command 3 | Encoder send position values 

Encoder-1 Singleturn Angle: 239.197067261000, received safety crc:0xaa18, calculated safety crc:0xc524, e_w:0x3, sign-of-life counter: 7

CRC Status: failure, crc error count: 1

Thanks

Alan I

Alan

Okay, we will check this and get back to you by next Tuesday.

Regards

Dhaval

Alan

Please note that the CPW and SPW is implemented by assuming 2 encoders connected in daisy chain (SPW will be sent by enc0 and CPW will be sent by enc1). So user has to provide 2nd encoder data length also according to the CPW data bit length.

Steps needed to be followed:

1) Enter enc0 data length corresponding to SPW data bit width -- SPW configuration - Menu option #1

2) Enter enc1 data length corresponding to CPW data bit width -- CPW configuration - Menu option #1 --> Assumption is CPW is sent as a second encoder response.

3) Enable safety using control communication - No need to perform this step if safety is enabled by default. - Menu option #6

4) Enable safety (for application purpose) by entering "1" for "enc0" and "0" for "enc1" as explained in sample log "BISS-C Sample Output when safety is enabled" - Menu option #7

5) Then request for position data - Menu option #3

Results need to interpret as: enc0 result is nothing but SPW and enc1 result is nothing but CPW.

This assumption is mentioned in https://software-dl.ti.com/processor-industrial-sw/esd/motor_control_sdk/am243x/09_02_00_09/docs/api_guide_am243x/BISSC_DESIGN.html under "Firmware Architecture" section while explaining the safety flow.

Regards

Dhaval

Hi Dhaval

Thank you for the guidance.  I am now able to read encoder with safety.

Channel 0:

Encoder-1 Singleturn Angle: 263.392639160000, received safety crc:0xd0fe, calculated safety crc:0xd0fe, e_w:0x3, sign-of-life counter: 32

CRC Status: success, crc error count: 1

Encoder-2 Singleturn Angle: 263.392639160000, crc:0x27, otf crc:0x27, e_w:0x3

CRC Status: success, crc error count: 0

 One other question on encoder numbering, it is meant to be reversed? If we look at data stream, I believed the BiSS Controller received CPW before SPW

Thanks

Alan I

Alan

Alan Ismail said:

 One other question on encoder numbering, it is meant to be reversed? If we look at data stream, I believed the BiSS Controller received CPW before SPW

Can you share a logic analyzer/scope capture for the data stream for us to review?

Regards

Dhaval

Hi Dhaval

Sorry for late reply

I meant , if we look at protocol data stream. 

CPW words are earlier than SPW words

Also, in real world application. Safety Encoder  ( with both CPW+SPW) can be used in non-safe environment by reading only the 1st half of data stream which only contains CPW.

In BiSS Master FPGA  documentation, the CPW and SPW are referred as 2 devices daisy chained together to form a single encoder.

Thank you

Alan I

Alan

Alan Ismail said:

In BiSS Master FPGA  documentation, the CPW and SPW are referred as 2 devices daisy chained together to form a single encoder.

Yes, this is what we referred to and we have implemented the same.

I did not understand your question fully. Can you explain more on what do you mean by encoder numbering reversal here?

Regards

Dhaval

Hi Dhaval

Sorry for late reply

Using BiSS diagnotic  safety option assume SPW in encoder 0 and CPW in encoder 1 which is in reverse to physical data stream sequence

Thanks

Alan I