TMS320F28P650DK: TMS320F28P650DK PTO-QepDiv application

Hi Yan,

During our testing, we did not specify minimum input frequency, only the maximum, since there are many ways to remedy the lower frequency limit but very few to remedy the upper limit. The concern with lower frequency would be that the counter on the CLB is 32-bits wide, so if the frequency is too low it may cause the CLB counter to overflow instead of being reset on the input edge. To remedy this, you can use one of the unused counters in the design to implement a down sampling mechanism, but this will have an impact on the maximum input frequency. You could also leverage the extra counter to implement a cascaded counter which should increase the CLB counter from 32-bit to 64-bits wide which will help support lower input frequencies. If you have a lower frequency limit in mind, that can help to understand if this will be a concern

Regards,

Peter

Hi Peter,

      Thanks, We encouter  problem at customer site use PTO-Abs2Qep function, Maybe  software calculation delay reason, Abs2Qep output QEP-I signal is not very accurate, So we want to change  QEP-I signal generated mode, QEP-I signal don't need software calculation,   QEP-I signal source come from external encoder's signal ,The Abs2Qep QEP-I signal only select EQEP_I signal , Abs2Qep expand EQEP_I signal's width then output .  signal width can be set from software interface, This is our requirement, Can TI expert to make the changes?  

Sincerely Yan junjie

Hi Yan,

Do you have a scope waveform to illustrate the issue you are seeing? I have seen issues related to the released Abs2Qep solution so I have created a separate software which has a couple of feature improvements, I am planning to push this code update to the MotorControl SDK in the future but can provide the code as a reference example if desired

Regards,

Peter

Hi Peter,

       I don't have scope waveform, I think because this reason, If servodrive use linear motor with incremental ABZ encoder feedback, The Abs2Qep module generate QEP_I index signal was virtual signal, can't indicate encoder's actual index signal expressed actual position on linear motor. So we need Abs2Qep QEP_I signal can select from EQEPn_I ,This signal connected external incremental ABZ encoder feedback's actual index signal.  the signal 's high level's width can be extended. 

Sincerely Yan junjie

Hi Yan,

Can you please have customer test out this software example: midea_pto_abs2qep_v2.zip

The changes are as follows

- this corrects issue where A and B output were not even/symmetrical

- this corrects issue where Z is not gated to A and B waveforms

I think the changes to Z output, possibly this will resolve issue you are seeing where Z output is delayed, since it is now aligned to A/B edges. Please let me know if you have any issue with this

Regards,

Peter

Hi Peter,

   Thanks !The changes can improve the signal's symmetry,we can do some test. but can't resolve customer site's problem we encountered.   Servodrive 's Abs2Qep generated QEP_I index signal  need connected to customer PLC equipment.  Abs2Qep generated QEP_I index signal need simultaneous with linear motor encoder's index signal. So Abs2Qep generated QEP_I index signal  can't  be virtual signal generated by software calculation.  

Sincerely Yan junjie

Hi Yan,

In that case, can the customer reconfigure the Abs2Qep example to pass through the index signal then. This can be done by reconfiguring the OUTPUTXBAR to take the input of the index signal, rather than using the software generated signal. Since typically the absolute encoders we have designed the software typically don't have the external index signal

Regards,

Peter