Part Number: TMS320F28388D
Other Parts Discussed in Thread: C2000WARE, LM4132
I use 4 channels of the ADC_A unit to drive a SinCos encoder. This unit is operated with a resolution of 16 bits and the channels are in differential mode (2 sine & 2 cosine). The ADC samples synchron in a 16kHz grid (every 62.5us) by a SOC pulse generated through a PWM unit.
In addition, the COMPSS unit is used to generate a digital signal which is counted by the eQEP later. The comparator is operated with the sine/cosine and the corresponding negative signal of those at the inputs respectively.
The ADC works and gives me good results. The problem, the CMPSS unit is influenced by the ADC. This means that the signals coming out of the comparator are heavily disturbed. I can't filter them out, even with the highest hysteresis level.
But if I switch off the ADC unit, the signals from the comparator are very good.
The problem always occurs at the zero crossings of each period.
The following pictures helps to shows this problem. The first two signals are for the Sin and Sin Not tracks, directly from the encoder. The 3rd track is the digital signal which is generated by the comparator. The next 3 are analogous for cosine.
The problem can be seen in the detailed view. With each zero crossing of an analogue track, you can see that there are many glitches before the signal levels out properly.
If I switch off the ADC unit and look at the output signal of the comparator again, the result looks much better.
What can I do that I can use these two units together?
