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lucabaldini / xpedaq

Data acquisition software for the X-ray polarimetry explorers
GNU General Public License v2.0
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Glitch in the microsecond bytes out of the FPGA #150

Open lucabaldini opened 7 years ago

lucabaldini commented 7 years ago

Not sure whether this is new or we've seen it in the past, but we have observed temporary glitches in the two microsecond bytes in the binary files for run 001_0000494.

Originally we realized there was a problem because the timestamps for the run were distributed over some 9 (!) days. A closer inspection of the root file from Pixy showed a fair number of jumps in the timestamps

root [14] tree->Scan("fEventId:fTrigWindow:fTimeStamp-1485757627.0013136", "fEventId > 56820")
************************************************
*    Row   *  fEventId * fTrigWind * fTimeStam *
************************************************
*    56820 *     56821 *       440 * 656.51686 *
*    56821 *     56822 *       672 * 656.53888 *
*    56822 *     56823 *       572 * 656.54138 *
*    56823 *     56824 *       672 * 656.54655 *
*    56824 *     56825 *       660 * 656.54937 * <----- glitch
*    56825 *     56826 *       672 * 3663.0494 *
*    56826 *     56827 *       672 * 4092.5383 *
*    56827 *     56828 *       624 * 4092.5511 *
*    56828 *     56829 *       720 * 4092.5942 *
*    56829 *     56830 *       672 * 4092.5982 *
*    56830 *     56831 *       572 * 4092.6054 *

The root cause of the problem was actually traced back to a problem in the binary file

56826 - buffer  6623, w( 68,   0)--( 89,  19), 440 px, t = 656518175 us
56827 - buffer  6623, w(178, 224)--(201, 251), 672 px, t = 656540198 us
56828 - buffer  6623, w(152,  24)--(173,  49), 572 px, t = 656542695 us
56829 - buffer  6623, w(204, 294)--(227, 321), 672 px, t = 656547872 us
56830 - buffer  6623, w(252, 278)--(273, 307), 660 px, t = 656550688 us  
56831 - buffer  6623, w(186,  90)--(209, 117), 672 px, t = 227076914 us  <----- glitch
56832 - buffer  6623, w(126, 250)--(149, 277), 672 px, t = 656565815 us
56833 - buffer  6623, w(  6, 236)--( 29, 261), 624 px, t = 656578632 us
56834 - buffer  6624, w(208, 234)--(231, 263), 720 px, t = 656621679 us
56835 - buffer  6624, w( 76,  36)--( 99,  63), 672 px, t = 656625738 us
56836 - buffer  6624, w(  6, 266)--( 27, 291), 572 px, t = 656632939 us

(Mind the mismatch in the event number is due to the fact that in Pixy we do not write in the output file events with no clusters.)