Thread scheduler for PID period control ?

[gpetilli]

Originally Posted by Joe Ross

In addition, what method did you use to get the time?



What computer did you run the DS on?

It was a windows 7 lenovo - not sure the exact model but not more than two years old and definitely not a netbook. We did this tethered, not on WiFi.

[Joe Ross]

I just ran the following code:

    double prevTime = 0;
    public void teleopPeriodic() {
        double time = Timer.getFPGATimestamp();
        System.out.println(time-prevTime);
        prevTime=time;
    }

And got the following output:

[cRIO] 0.014032000000000266
[cRIO] 0.020156000000000063
[cRIO] 0.02008299999999963
[cRIO] 0.019773999999998182
[cRIO] 0.019995999999999015
[cRIO] 0.020203999999999667
[cRIO] 0.01987100000000197
[cRIO] 0.020114999999996996
[cRIO] 0.02004800000000273
[cRIO] 0.02036799999999772
[cRIO] 0.019611000000004708
[cRIO] 0.019765999999997064
[cRIO] 0.019995999999999015
[cRIO] 0.019989000000002477
[cRIO] 0.02004999999999768
[cRIO] 0.019984999999998365
[cRIO] 0.0200450000000032
[cRIO] 0.019925000000000637
[cRIO] 0.019964999999999122
[cRIO] 0.020108999999997934
[cRIO] 0.020091000000000747
[cRIO] 0.019836000000005072
[cRIO] 0.019992999999999483
[cRIO] 0.02026199999999534
[cRIO] 0.019725000000001103
[cRIO] 0.019995999999999015
[cRIO] 0.020110000000002515
[cRIO] 0.019950999999998942
[cRIO] 0.019914999999997463
[cRIO] 0.020150000000001
[cRIO] 0.019964999999999122
[cRIO] 0.019953000000000998
[cRIO] 0.02007000000000403
[cRIO] 0.023333000000000936
[cRIO] 0.016567999999999472
[cRIO] 0.019990999999997427
[cRIO] 0.019987999999997896
[cRIO] 0.02036199999999866
[cRIO] 0.019624000000000308
[cRIO] 0.020121000000003164
[cRIO] 0.02003100000000302
[cRIO] 0.01989399999999364
[cRIO] 0.020100000000006446
[cRIO] 0.019787999999998362
[cRIO] 0.02019099999999696
[cRIO] 0.019915000000004568
[cRIO] 0.019970999999998185
[cRIO] 0.020511999999996533
[cRIO] 0.019507000000004382
[cRIO] 0.020938999999998487
[cRIO] 0.01930399999999821
[cRIO] 0.020080999999997573
[cRIO] 0.019986000000002946
[cRIO] 0.0199089999999984
[cRIO] 0.020019000000004894
[cRIO] 0.019859999999994216
[cRIO] 0.020032000000000494
[cRIO] 0.020005000000004713
[cRIO] 0.01986199999999627
[cRIO] 0.020163000000003706
[cRIO] 0.020060000000000855
[cRIO] 0.019814999999994143
[cRIO] 0.02012300000000522
[cRIO] 0.019915999999994938
[cRIO] 0.019857999999999265
[cRIO] 0.020221000000006484
[cRIO] 0.01981199999999461
[cRIO] 0.02013300000000129
[cRIO] 0.020065000000002442
[cRIO] 0.01982299999999526
[cRIO] 0.020184000000000424
[cRIO] 0.019892000000005794
[cRIO] 0.02009899999999476
[cRIO] 0.01988500000000215
[cRIO] 0.02012200000000064
[cRIO] 0.019989999999999952
[cRIO] 0.019863999999998327
[cRIO] 0.02014700000000147
[cRIO] 0.019995999999999015
[cRIO] 0.020175999999999306
[cRIO] 0.019838000000000022
[cRIO] 0.019888999999999157
[cRIO] 0.020115000000004102
[cRIO] 0.020016999999995733
[cRIO] 0.01998400000000089
[cRIO] 0.020042000000003668
[cRIO] 0.01999999999999602
[cRIO] 0.01975800000000305
[cRIO] 0.0200139999999962
[cRIO] 0.020180000000003417
[cRIO] 0.019850999999995622
[cRIO] 0.02010900000000504
[cRIO] 0.020080000000000098
[cRIO] 0.020117999999996528
[cRIO] 0.019851000000002728
[cRIO] 0.020186999999999955
[cRIO] 0.020111999999997465
[cRIO] 0.020330999999998767
[cRIO] 0.019290000000005136
[cRIO] 0.02057199999999426
[cRIO] 0.019626000000002364
[cRIO] 0.01993500000000381
[cRIO] 0.020097999999997285
[cRIO] 0.021600999999996873
[cRIO] 0.01841500000000451
[cRIO] 0.019878999999995983
[cRIO] 0.020146000000003994
[cRIO] 0.020054000000001793
[cRIO] 0.020954999999993618
[cRIO] 0.018789000000005274
[cRIO] 0.022835000000000605
[cRIO] 0.017481999999994002
[cRIO] 0.019851000000002728
[cRIO] 0.019829999999998904
[cRIO] 0.02016400000000118
[cRIO] 0.020018000000000313
[cRIO] 0.019930000000002224
[cRIO] 0.020049000000000206
[cRIO] 0.020051999999999737
[cRIO] 0.02079599999999715
[cRIO] 0.019050999999997487
[cRIO] 0.022271000000003482
[cRIO] 0.01766800000000046
[cRIO] 0.02002000000000237
[cRIO] 0.020178999999998837
[cRIO] 0.02001899999999779
[cRIO] 0.019908000000000925
[cRIO] 0.020046000000000674
[cRIO] 0.020044999999996094
[cRIO] 0.019980000000003884
[cRIO] 0.01983699999999544
[cRIO] 0.02458000000000027
[cRIO] 0.0157040000000066
[cRIO] 0.01980599999999555
[cRIO] 0.020093000000002803
[cRIO] 0.0201279999999997
[cRIO] 0.019898999999995226
[cRIO] 0.020168000000005293
[cRIO] 0.019810999999997136
[cRIO] 0.020003000000002658
[cRIO] 0.019991999999994903
[cRIO] 0.022979000000006522
[cRIO] 0.01685799999999915
[cRIO] 0.020008999999994614
[cRIO] 0.019876000000003557
[cRIO] 0.02014599999999689
[cRIO] 0.020217000000002372
[cRIO] 0.020510000000001583
[cRIO] 0.019436999999996374
[cRIO] 0.020022000000004425
[cRIO] 0.01999699999999649
[cRIO] 0.019826999999999373
[cRIO] 0.019909000000005506
[cRIO] 0.02016599999999613
[cRIO] 0.01995600000000053
[cRIO] 0.02026299999999992
[cRIO] 0.019973999999997716
[cRIO] 0.019733999999999696
[cRIO] 0.020008000000004245
[cRIO] 0.020130000000001758
[cRIO] 0.0199439999999953
[cRIO] 0.01991699999999952
[cRIO] 0.020014000000003307
[cRIO] 0.02026499999999487
[cRIO] 0.020091000000000747
[cRIO] 0.019711000000000922
[cRIO] 0.02048200000000122
[cRIO] 0.019823999999999842
[cRIO] 0.020276000000002625
[cRIO] 0.019548000000000343
[cRIO] 0.020054999999999268
[cRIO] 0.021468999999996186
[cRIO] 0.01859900000000181
[cRIO] 0.019700000000000273
[cRIO] 0.019939000000000817
[cRIO] 0.021791000000000338
[cRIO] 0.018093999999997834
[cRIO] 0.020206999999999198
[cRIO] 0.019817000000003304
[cRIO] 0.02050700000000205
[cRIO] 0.020139999999997826
[cRIO] 0.022245999999995547
[cRIO] 0.017315000000003522
[cRIO] 0.01983200000000096
[cRIO] 0.02001200000000125
[cRIO] 0.02009699999999981
[cRIO] 0.019945999999997355
[cRIO] 0.020163000000003706
[cRIO] 0.019883000000000095
[cRIO] 0.01994699999999483
[cRIO] 0.020003000000002658
[cRIO] 0.020181000000000893
[cRIO] 0.01998400000000089
[cRIO] 0.019994999999994434
[cRIO] 0.01981800000000078
[cRIO] 0.020724999999998772
[cRIO] 0.01940400000000153
[cRIO] 0.020572000000001367
[cRIO] 0.019492999999997096
[cRIO] 0.020011000000003776
[cRIO] 0.02001200000000125
[cRIO] 0.019867999999995334
[cRIO] 0.01991699999999952
[cRIO] 0.020219000000004428
[cRIO] 0.019978999999999303
[cRIO] 0.02002199999999732
[cRIO] 0.019750999999999408
[cRIO] 0.02012500000000017
[cRIO] 0.020092000000005328
[cRIO] 0.020537999999994838
[cRIO] 0.019495000000006257
[cRIO] 0.020107999999993353
[cRIO] 0.019899999999999807
[cRIO] 0.020124000000002695
[cRIO] 0.020169000000002768
[cRIO] 0.019700000000000273
[cRIO] 0.020637000000000683
[cRIO] 0.01944199999999796
[cRIO] 0.01986800000000244
[cRIO] 0.020131999999996708
[cRIO] 0.020014000000003307
[cRIO] 0.01990499999999429
[cRIO] 0.02029100000000028
[cRIO] 0.019598999999999478
[cRIO] 0.020002000000005182
[cRIO] 0.02232999999999663
[cRIO] 0.017898000000002412
[cRIO] 0.020381000000000427
[cRIO] 0.01945299999999861
[cRIO] 0.019967000000001178
[cRIO] 0.02024799999999516
[cRIO] 0.019709000000005972
[cRIO] 0.01999399999999696
[cRIO] 0.020249999999997215
[cRIO] 0.019863000000000852
[cRIO] 0.020217000000002372
[cRIO] 0.019892999999996164
[cRIO] 0.020042000000003668
[cRIO] 0.019748999999997352
[cRIO] 0.020043000000001143
[cRIO] 0.0200010000000006
[cRIO] 0.020333000000000823
[cRIO] 0.019875999999996452
[cRIO] 0.019884000000004676
[cRIO] 0.020113000000002046
[cRIO] 0.019994999999994434
[cRIO] 0.02008400000000421
[cRIO] 0.02040299999999462
[cRIO] 0.019336000000002684
[cRIO] 0.020540000000004
[cRIO] 0.01947499999999991
[cRIO] 0.020902999999997007
[cRIO] 0.01910999999999774
[cRIO] 0.019978000000001828
[cRIO] 0.020012999999998726
[cRIO] 0.020107000000002984
[cRIO] 0.01981500000000125
[cRIO] 0.020117999999996528
[cRIO] 0.01991199999999793
[cRIO] 0.020054999999999268
[cRIO] 0.020019000000004894
[cRIO] 0.02013799999999577
[cRIO] 0.019870000000004495
[cRIO] 0.02012099999999606
[cRIO] 0.020061000000005436
[cRIO] 0.019942999999997824
[cRIO] 0.019940999999995768
[cRIO] 0.02003100000000302
[cRIO] 0.019827999999996848
[cRIO] 0.019962000000006697
[cRIO] 0.02714199999999778
[cRIO] 0.01292699999999769
[cRIO] 0.019863999999998327
[cRIO] 0.020138000000002876
[cRIO] 0.02063100000000162
[cRIO] 0.019636999999995908
[cRIO] 0.01994300000000493
[cRIO] 0.02027299999999599
[cRIO] 0.019710000000003447
[cRIO] 0.020027999999996382
[cRIO] 0.020064000000004967
[cRIO] 0.019843999999999085
[cRIO] 0.01997199999999566
[cRIO] 0.02011099999999999
[cRIO] 0.019913999999999987
[cRIO] 0.020194000000003598
[cRIO] 0.019945999999997355
[cRIO] 0.01988099999999804
[cRIO] 0.02000600000000219
[cRIO] 0.020093000000002803
[cRIO] 0.020111999999997465
[cRIO] 0.026910000000000878
[cRIO] 0.012717999999999563
[cRIO] 0.020026999999998907
[cRIO] 0.020040000000001612
[cRIO] 0.020037999999999556
[cRIO] 0.02022699999999844
[cRIO] 0.02054300000000353
[cRIO] 0.01946699999999879
[cRIO] 0.01999699999999649
[cRIO] 0.019892000000005794
[cRIO] 0.01996899999999613
[cRIO] 0.02007199999999898
[cRIO] 0.021723999999998966
[cRIO] 0.01812500000000483
[cRIO] 0.020227999999995916
[cRIO] 0.019947000000001935
[cRIO] 0.0199089999999984
[cRIO] 0.02003400000000255
[cRIO] 0.020015000000000782
[cRIO] 0.02004399999999862
[cRIO] 0.020769999999998845
[cRIO] 0.01921300000000059
[cRIO] 0.019786000000003412
[cRIO] 0.019997999999993965
[cRIO] 0.020124000000002695
[cRIO] 0.019961000000002116
[cRIO] 0.020072999999996455
[cRIO] 0.020029000000000963
[cRIO] 0.020017000000002838
[cRIO] 0.01980999999999966
[cRIO] 0.022269999999998902
[cRIO] 0.017738000000001364
[cRIO] 0.019945999999997355
[cRIO] 0.02023799999999909
[cRIO] 0.019825000000004422
[cRIO] 0.01999999999999602
[cRIO] 0.02022500000000349
[cRIO] 0.019962999999997066
[cRIO] 0.019761000000002582
[cRIO] 0.020324999999999704
[cRIO] 0.01984199999999703
[cRIO] 0.020082000000002154
[cRIO] 0.019743999999995765
[cRIO] 0.020238000000006195
[cRIO] 0.020014999999993677
[cRIO] 0.0198040000000006
[cRIO] 0.02026599999999945
[cRIO] 0.01972000000000662
[cRIO] 0.019998999999998546
[cRIO] 0.01994699999999483
[cRIO] 0.02109500000000253
[cRIO] 0.019206000000004053
[cRIO] 0.019966999999994073
[cRIO] 0.020003000000002658
[cRIO] 0.020752000000001658
[cRIO] 0.01915199999999828
[cRIO] 0.020476999999999634
[cRIO] 0.019496000000003733
[cRIO] 0.019954999999995948
[cRIO] 0.02003700000000208
[cRIO] 0.020058999999996274
[cRIO] 0.02009500000000486
[cRIO] 0.020039999999994507
[cRIO] 0.020006999999999664
[cRIO] 0.019711000000000922
[cRIO] 0.019989000000002477
[cRIO] 0.0201849999999979
[cRIO] 0.019786000000003412
[cRIO] 0.02016100000000165
[cRIO] 0.019966999999994073
[cRIO] 0.019948000000006516
[cRIO] 0.020086999999996635
[cRIO] 0.020040999999999087
[cRIO] 0.020315000000003636
[cRIO] 0.020910999999998126
[cRIO] 0.018869000000002245
[cRIO] 0.01991099999999335
[cRIO] 0.0198960000000028
[cRIO] 0.020060000000000855
[cRIO] 0.020119999999998583
[cRIO] 0.01984600000000114
[cRIO] 0.01997599999999977
[cRIO] 0.020156000000000063
[cRIO] 0.019992000000002008
[cRIO] 0.019875999999996452
[cRIO] 0.019952000000003522
[cRIO] 0.02003899999999703
[cRIO] 0.019950999999998942
[cRIO] 0.02415600000000495
[cRIO] 0.017558999999998548
[cRIO] 0.01820099999999769
[cRIO] 0.020138000000002876
[cRIO] 0.02014899999999642
[cRIO] 0.01997400000000482
[cRIO] 0.02056699999999978
[cRIO] 0.019649999999998613
[cRIO] 0.01983699999999544
[cRIO] 0.019916000000002043
[cRIO] 0.019925999999998112
[cRIO] 0.020104000000003452
[cRIO] 0.01996899999999613
[cRIO] 0.020089000000005797
[cRIO] 0.01988399999999757
[cRIO] 0.02015999999999707
[cRIO] 0.020121000000003164
[cRIO] 0.01988399999999757
[cRIO] 0.02070300000000458
[cRIO] 0.019280999999999437
[cRIO] 0.020150000000001
[cRIO] 0.0196550000000002
[cRIO] 0.020775000000000432
[cRIO] 0.019251999999994496
[cRIO] 0.02002600000000143
[cRIO] 0.019967000000001178
[cRIO] 0.020124000000002695
[cRIO] 0.019885999999999626
[cRIO] 0.02072099999999466
[cRIO] 0.01945100000000366
[cRIO] 0.01994499999999988
[cRIO] 0.02018600000000248
[cRIO] 0.019722999999999047
[cRIO] 0.02007499999999851
[cRIO] 0.02379799999999932
[cRIO] 0.016322999999999865
[cRIO] 0.019782999999996775
[cRIO] 0.02015100000000558
[cRIO] 0.020270999999993933
[cRIO] 0.019754000000006045
[cRIO] 0.019815999999998724
[cRIO] 0.020310999999999524
[cRIO] 0.01969700000000074
[cRIO] 0.020060000000000855
[cRIO] 0.01984799999999609
[cRIO] 0.02037299999999931
[cRIO] 0.019815999999998724
[cRIO] 0.01990700000000345
[cRIO] 0.020332000000003347
[cRIO] 0.01992499999999353
[cRIO] 0.02002400000000648
[cRIO] 0.020189999999999486
[cRIO] 0.019765999999997064
[cRIO] 0.0204039999999992
[cRIO] 0.019517999999997926
[cRIO] 0.019838000000000022
[cRIO] 0.020096000000002334
[cRIO] 0.01993500000000381
[cRIO] 0.01998299999999631
[cRIO] 0.020029000000000963
[cRIO] 0.019978000000001828
[cRIO] 0.020064999999995337
[cRIO] 0.019913999999999987
[cRIO] 0.020009999999999195
[cRIO] 0.0201720000000023
[cRIO] 0.019997000000003595
[cRIO] 0.022979999999996892
[cRIO] 0.016818000000000666
[cRIO] 0.020387999999996964
[cRIO] 0.01974100000000334
[cRIO] 0.02002199999999732
[cRIO] 0.020033000000005075
[cRIO] 0.01996399999999454
[cRIO] 0.020049000000000206
[cRIO] 0.019928000000000168
[cRIO] 0.02005900000000338
[cRIO] 0.0199439999999953
[cRIO] 0.019925000000000637
[cRIO] 0.02031700000000569
[cRIO] 0.0196899999999971
[cRIO] 0.020135000000003345
[cRIO] 0.020114999999996996
[cRIO] 0.019871999999999446
[cRIO] 0.020012999999998726
[cRIO] 0.019944000000002404
[cRIO] 0.02004699999999815
[cRIO] 0.020015999999998257
[cRIO] 0.019809000000002186
[cRIO] 0.020138000000002876
[cRIO] 0.021020999999997514
[cRIO] 0.019089000000001022
[cRIO] 0.020018000000000313
[cRIO] 0.020696000000000936
[cRIO] 0.019242999999995902
[cRIO] 0.01981500000000125
[cRIO] 0.020102000000001397
[cRIO] 0.01995600000000053
[cRIO] 0.020029000000000963
[cRIO] 0.020207999999996673
[cRIO] 0.019660000000001787
[cRIO] 0.020089999999996166
[cRIO] 0.020042000000003668
[cRIO] 0.019973999999997716
[cRIO] 0.020473000000002628
[cRIO] 0.019314000000001386
[cRIO] 0.020022999999994795
[cRIO] 0.022302000000003375
[cRIO] 0.017952000000001078
[cRIO] 0.0197819999999993
[cRIO] 0.020102000000001397
[cRIO] 0.019888999999999157
[cRIO] 0.020230999999995447
[cRIO] 0.019927000000002693
[cRIO] 0.019983000000003415
[cRIO] 0.020053999999994687
[cRIO] 0.019967000000001178
[cRIO] 0.020789000000000613
[cRIO] 0.019309999999997274
[cRIO] 0.020400000000002194
[cRIO] 0.01931199999999933
[cRIO] 0.020124000000002695
[cRIO] 0.020106999999995878
[cRIO] 0.01998100000000136
[cRIO] 0.019860999999998796
[cRIO] 0.020028000000003487
[cRIO] 0.020136999999998295
[cRIO] 0.020029999999998438
[cRIO] 0.01998200000000594
[cRIO] 0.01994999999999436
[cRIO] 0.02002600000000143
[cRIO] 0.020383000000002482
[cRIO] 0.022705000000001974
[cRIO] 0.017861999999993827
[cRIO] 0.0212670000000017
[cRIO] 0.017876000000001113
[cRIO] 0.0199089999999984
[cRIO] 0.018914999999999793
[cRIO] 0.020319000000000642
[cRIO] 0.02000900000000172
[cRIO] 0.019713000000002978
[cRIO] 0.020324999999999704
[cRIO] 0.019955999999993423
[cRIO] 0.021434000000006392
[cRIO] 0.018278999999999712
[cRIO] 0.019920999999996525
[cRIO] 0.020091000000000747
[cRIO] 0.020014000000003307
[cRIO] 0.02043099999999498
[cRIO] 0.020060000000000855
[cRIO] 0.020884000000002345
[cRIO] 0.01870699999999914
[cRIO] 0.020175999999999306
[cRIO] 0.021906000000001313
[cRIO] 0.018057999999996355
[cRIO] 0.01976499999999959
[cRIO] 0.02005900000000338
[cRIO] 0.02006399999999786
[cRIO] 0.019984999999998365
[cRIO] 0.020016000000005363
[cRIO] 0.019852000000000203
[cRIO] 0.01999699999999649
[cRIO] 0.020014000000003307
[cRIO] 0.02085999999999899
[cRIO] 0.019115999999996802
[cRIO] 0.01998100000000136
[cRIO] 0.02034799999999848
[cRIO] 0.019743000000005395
[cRIO] 0.019969999999993604
[cRIO] 0.020834000000000685
[cRIO] 0.019154000000000337
[cRIO] 0.020351000000005115
[cRIO] 0.019782999999996775
[cRIO] 0.019863999999998327
[cRIO] 0.01995900000000006
[cRIO] 0.020419000000003962
[cRIO] 0.01973499999999717
[cRIO] 0.020254999999998802
[cRIO] 0.020149000000003525
[cRIO] 0.01984799999999609
[cRIO] 0.019854999999999734
[cRIO] 0.019978000000001828
[cRIO] 0.020330999999998767
[cRIO] 0.019764000000002113
[cRIO] 0.019944000000002404
[cRIO] 0.020730999999997834
[cRIO] 0.019033999999997775
[cRIO] 0.020793000000004724
[cRIO] 0.019093999999995503
[cRIO] 0.020068000000001973
[cRIO] 0.01989300000000327
[cRIO] 0.020155999999992957
[cRIO] 0.01997400000000482
[cRIO] 0.020041999999996563
[cRIO] 0.020545000000005587
[cRIO] 0.02011299999999494
[cRIO] 0.019421000000001243
[cRIO] 0.019908000000000925
[cRIO] 0.02002199999999732
[cRIO] 0.01991999999999905
[cRIO] 0.020029000000000963
[cRIO] 0.019992999999999483
[cRIO] 0.020448000000001798
[cRIO] 0.01956700000000211
[cRIO] 0.020226000000000965
[cRIO] 0.020052999999997212
[cRIO] 0.019679000000003555
[cRIO] 0.020129999999994652
[cRIO] 0.020181000000000893
[cRIO] 0.01988099999999804
[cRIO] 0.019881000000005145
[cRIO] 0.020089999999996166
[cRIO] 0.020166000000003237
[cRIO] 0.019773999999998182
[cRIO] 0.020504999999999995
[cRIO] 0.019983000000003415
[cRIO] 0.02005699999999422
[cRIO] 0.019624000000000308
[cRIO] 0.020502000000000464
[cRIO] 0.020051999999999737
[cRIO] 0.019203000000004522
[cRIO] 0.02033000000000129
[cRIO] 0.01980599999999555
[cRIO] 0.022809999999999775
[cRIO] 0.017161000000001536
[cRIO] 0.019911000000000456
[cRIO] 0.020144999999999413
[cRIO] 0.02002199999999732
[cRIO] 0.01988200000000262
[cRIO] 0.020184000000000424
[cRIO] 0.019803000000003124
[cRIO] 0.020103999999996347
[cRIO] 0.019919000000001574
[cRIO] 0.020341999999999416
[cRIO] 0.019807999999997605
[cRIO] 0.01982100000000031
[cRIO] 0.02013900000000035
[cRIO] 0.02006200000000291
[cRIO] 0.020164999999998656
[cRIO] 0.019975000000002296
[cRIO] 0.019897000000000276
[cRIO] 0.020015999999998257
[cRIO] 0.020395000000000607
[cRIO] 0.019925999999998112
[cRIO] 0.019846999999998616
[cRIO] 0.019803000000003124
[cRIO] 0.019911000000000456
[cRIO] 0.020461999999994873
[cRIO] 0.019856000000004315
[cRIO] 0.01998899999999537
[cRIO] 0.019852000000000203
[cRIO] 0.019776000000000238
[cRIO] 0.020119000000001108
[cRIO] 0.02020300000000219
[cRIO] 0.019680999999998505

How does your test differ?

[Ether]

Originally Posted by Joe Ross

I just ran the following code:

    double prevTime = 0;
    public void teleopPeriodic() {
        double time = Timer.getFPGATimestamp();
        System.out.println(time-prevTime);
        prevTime=time;
    }

And got the following output...

I took the liberty of plotting it. Attached.

[gpetilli]

That is what I expected, which is why I was confused. I should get the 4 slot cRIO today and will retry. I know the older 8 slot was slower, but it seems strange that they would change the driver station behavior to update less often.

[Joe Ross]

Originally Posted by gpetilli

That is what I expected, which is why I was confused. I should get the 4 slot cRIO today and will retry. I know the older 8 slot was slower, but it seems strange that they would change the driver station behavior to update less often.

My test was run on an 8-slot. The 8-slot has less ram, but the same processor. In this test, it is not slower.

[gpetilli]

Originally Posted by Joe Ross

My test was run on an 8-slot. The 8-slot has less ram, but the same processor. In this test, it is not slower.

Thanks for the feedback, i will have them re-run the test. BTW: what period do you use for your PID loops?

[gpetilli]

Originally Posted by Joe Ross

I just ran the following code:

    double prevTime = 0;
    public void teleopPeriodic() {
        double time = Timer.getFPGATimestamp();
        System.out.println(time-prevTime);
        prevTime=time;
    }

How does your test differ?

The major difference is we are reading an I2C 9DOF IMU model GY85. Works great, but maybe the I2C is slowing things down. I did a quick estimate and thought the time would be about 1 to 2ms, but maybe there is more overhead than I guessed.

I guess we just need to try the measurements again.

[Greg McKaskle]

Just to reiterate. The 8-slot has less RAM and is a model variation of the same FreeScale processor, meaning it has a less cache. For most situations, it is the same speed.

Greg McKaskle

[wireties]

When you create a task and put it in a loop with a delay, the delay is subject to the resolution of the system clock (which is 10ms). So a request to delay for 20ms would have considerable variation. The system is waiting for two clock ticks which could happen in a little over 10ms or a little under 30ms.

The PID class does not use delays, instead it uses the timer OS libraries (last I looked). These fire in the context of the tick timer interrupt routine and are more periodic. The first PID timer callback may run at a variable time after enabling but it will run very periodically afterwards. Does that make sense?

The operating system does have a higher resolution timer (the auxiliary timer) for custom purposes. It is not used by the base OS. And perhaps NI built a service on top of the the auxiliary timer. Plus there is normally a third timer only used for timestamps. But the base timers work as described above.

The periodicity of the messages from the DS is dependent on many things. Ethernet is not strictly deterministic. The teleop loops start after a semaphore is given once the code on the cRIO processes an incoming message and the data is available.

HTH

[Joe Johnson]

I am not sure why but the autogenerated code from RobotBuilder does not include the feed forward gain, Kf, and the loop period, so they default to 0 and 50ms.

Here is a code snippet:
public Launch() {
super("Launch", Kp, Ki, Kd, Kf, 0.01);

Note that we had 0.005 as the period at first and it was acting squirrely. I think we were having the PID loop take too much of the CPU time. When we backed off to 10ms, life was good.

YMMV.

Joe J.

[tinybob20]

Hi,

we tried using the getFPGATimestamp() instead of the basic .get(), and we were able to get values around 11 - 16 ms for our timed PID loop with the scheduler set to 10ms.

in teleopPeriodic we got values around 21 - 23 ms.

[gpetilli]

Originally Posted by Joe Ross

I just ran the following code:

    double prevTime = 0;
    public void teleopPeriodic() {
        double time = Timer.getFPGATimestamp();
        System.out.println(time-prevTime);
        prevTime=time;
    }

How does your test differ?

Joe,

Post #16 above is from the student we had redo the test. The differences between our original test and this one are switching from an OS timer to the FPGA timer like your code and the new test has the full PID drive code. The ~50ms DS measurement that originally had me questioning what was going on is now ~20ms as expected.
The timed loop measurement is also faster (11->16ms instead of >20ms) , but not the 10ms that we asked for. At this point we intend to set the timed PID loop to 15ms instead of 10ms to hopefully stay within the computation limit of the cRIO. Thanks for your help and example code for more accurate measurements.

[Greg McKaskle]

The timer doesn't control the rate of the loop. It merely measures the time from one execution to the next. If you have code within teleop that takes more than 20ms to run, you will skip DS updates. I see this quite often on team DS logs, even teams from Einstein. It would be odd that the periodic is not a multiple of 20ms. And unless the network and/or DS are stressed out, I'd expect jitter numbers like Joe showed above.

I'm not sure how Java PID does its scheduling, and when teams spawn another thread and set its rate, I'm not sure what they are using to schedule.

Team 358's article is about timing using LabVIEW. LabVIEW has two different schedulers. One has ms level resolution and is used for general VI execution. It uses a pool of threads at various priorities, and the LV wait and wait ms functions and a plain while loop will operate in this scheduler. The TimedLoop uses its own scheduler that runs at an elevated priority and has advanced scheduling options -- quite advanced. It can schedule at sub millisecond periods and implements a variety of policies. Only Timed structure code runs in this scheduler.

The timed loop is also instrumented so that it is easy to determine start and stop times, missed deadlines, adjust priorities and other things. I'd highly recommend that you instrument your PID not only to measure its actual period, but also its execution time. You could also do this with a profiler if you have one. This will let you know the cost of the operation you are scheduling.

Greg McKaskle

[gpetilli]

Originally Posted by Greg McKaskle

The timer doesn't control the rate of the loop. It merely measures the time from one execution to the next. If you have code within teleop that takes more than 20ms to run, you will skip DS updates. I see this quite often on team DS logs, even teams from Einstein. It would be odd that the periodic is not a multiple of 20ms. And unless the network and/or DS are stressed out, I'd expect jitter numbers like Joe showed above.

I'm not sure how Java PID does its scheduling, and when teams spawn another thread and set its rate, I'm not sure what they are using to schedule.

Team 358's article is about timing using LabVIEW. LabVIEW has two different schedulers. One has ms level resolution and is used for general VI execution. It uses a pool of threads at various priorities, and the LV wait and wait ms functions and a plain while loop will operate in this scheduler. The TimedLoop uses its own scheduler that runs at an elevated priority and has advanced scheduling options -- quite advanced. It can schedule at sub millisecond periods and implements a variety of policies. Only Timed structure code runs in this scheduler.

The timed loop is also instrumented so that it is easy to determine start and stop times, missed deadlines, adjust priorities and other things. I'd highly recommend that you instrument your PID not only to measure its actual period, but also its execution time. You could also do this with a profiler if you have one. This will let you know the cost of the operation you are scheduling.

Greg McKaskle

Yes, we understand that the timer is a free-running stop watch that we are using to instrument our loops. This is why in the OP we were concerned that the teleopPeriodic was reporting 50ms on a program that did nothing but report the time while running tethered. Switching to the FPGA timer now correctly reports a 20ms teleopPeriodic rate.

What we are trying to do is create another thread outside of teleopPeriodic for doing the PID calculations at a faster, more consistent rate. We believe we have accomplished this in JAVA. We were hoping to achieve a 10ms period but appear to be processor limited to 15ms. This seems like a long time given other teams are talking about 5ms loops (not sure if they measured actual loop times). We do have some calculations in our loop, but I would not have expected it to limit the period by so much. We are looking into the bottleneck but time on the robot is limited with bag & tag in a few days. Worst case, the performance with 15ms seems fine for competition.

[Ether]

Originally Posted by gpetilli

What we are trying to do is create another thread outside of teleopPeriodic for doing the PID calculations at a faster, more consistent rate.

Just a heads-up in case you have not yet seen this post:

http://www.chiefdelphi.com/forums/sh....php?p=1342439