I have a strange result from the ADC:

Help wellcome.

Vref = EXT 1.25 V

SINGLEOFFSET = 0x8

SINGLEOFFSETINV = 0xA

SINGLEGAIN = 0x00

Problems:

1. From 0,625 to 1.25 OK.   < 0.625 V allways 2048 ?!?

2. can't calibrate gain to 4096 mostly to 4079....4081

SINGLECTRLX - VREFSEL = 2

                            VREFATTFIX = 0

                            VREFFATT = 8

                            VINATT = 14

                            DVL = 0

                            FIFOOFACT = 1

                            PRSMODE = 0

                            PRSSEL = 0

SINGLECTRL  - REP = 0

                           DIFF = 0

                           ADJ = 0

                           RES = 3

                           REF = 7

                           POSSEL = 0x87

                           NEGSEL = 0xFF

                           AT = 5

                           PRSEN = 0

                           CMPEN = 0

CTRL  -  WARMUPMODE = 3

               SINGLEEDWAWU = 0

              SCANDMAWO = 0

              TAILGATE = 0

              ASYNCCLKEN = 0

              ADCCLKMODE = 0

              PRESC = 0

              TMEBASE = 5

              OVSRSEL = 6

              CHCONMODE = 0

 Anybody any idea ?

Thanks

arnold