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HELP!   I can read only 2 of 6 channels on ADC, freerunning mode. !???

Question asked by Peter Gawell on Jun 28, 2011
Latest reply on Jun 30, 2011 by Peter Gawell

Hi everyone !

I am desperate for som help regarding a VERY mysterious bug.

I get perfectly OK ADC input from ch0 and ch1, but ch2-ch5 are dead  ( ! )

No interrupts, just SCAN mode ch0 to ch5, where I get good values in ATDDR0 and ATDDR1 but

zeroes or small static values in ATDDR2, ATDDR3, ATDDR4 and ATDDR5.

I mean how can it be working for two channels and not with six ??  Since the two is working, inits, clock, I/O

frerunning mode, ref modes and so on must be right.   It should be only ATDCTL3 "conversion sequence length"

bits S1C-S8C that sets how many channels to sample.  I have quadruplechecked they are 0110 = 6 channels.

(ATDCTL3 = 32h (50d)).  SCAN=1, MULTichannel =1  (ATDCTL5 = B0h (176d))

I have developed two separate projects, both with a 9S12E64 mpu, relocatable assembler, and they show exactly the same bug.  Everything else, DACs, SCIO, std IO works like a charm.

Softwares is made completely from scratch, each proj individually - i did not use one as base for the other.

I used PE to autogenerate initialization.   See code snippets below.

Full code attached.


Please help, i'm going insane !!  :smileytongue:


Proj facts:

Relocateable Assmbler

CW IDE version 5.9.0 build 2836

MPU:  MC9S12E64CFU   16Mhz osc, 8Mhz int


PE autogenerated code:


  ; ### Init_ADC init code
        ; ATDCTL3: S8C=0,S4C=1,S2C=1,S1C=0,FIFO=0,FRZ1=1,FRZ0=0
        MOVB    #50,ATDCTL3                                       
        ; ATDCTL4: SRES8=0,SMP1=0,SMP0=1,PRS4=0,PRS3=0,PRS2=1,PRS1=0,PRS0=1
        MOVB    #37,ATDCTL4                                       
        MOVB    #128,ATDCTL2                                       
  ;   The following delay loop generates a delay of approx. 20us, which is needed for
  ;   the module to recover from power down state.
    ; * Delay
    ; *   - requested                  : 20 us @ 8MHz,
    ; *   - possible                   : 160 c, 20000 ns
    ; */
    pshd                               ; (2 c: 250 ns) backup D */



        ; ATDCTL5: DJM=1,DSGN=0,SCAN=1,MULT=1,CD=0,CC=0,CB=0,CA=0
        MOVB    #176,ATDCTL5                                       
  ; ### Init_FLASH init code




;*** Read & average (oversampling) analog inputs

ReadAD ldaa ad_seq ; 0 - read channel 0
 bne _ad10
 ldd ATDDR0 ; read result data register 0 (two bytes)
 ldx ad_bufp0 ; get pointer
 std 2,X+ ; store reading into filter array
 cpx #ad_buf0e ; end of array ?
 bne _ad00 ; BI not
 ldx #ad_buf0 ; else reinit pointer
_ad00 stx ad_bufp0 ; save pointer
 ldd #0
 ldx #ad_buf0
_ad02 addd 2,X+ ; sum all values
 cpx #ad_buf0e ; end of array ?
 bne _ad02 ; BI not
 std ad_temp
 inc ad_seq


_ad10 cmpa #1 ; 1 - read channel 1
 bne _ad20
 ldd ATDDR1 ; read result data register 1 (two bytes)
 ldx ad_bufp1 ; get pointer
 std 2,X+
 cpx #ad_buf1e ; end of array ?
 bne _ad11 ; BI not
 ldx #ad_buf1
_ad11 stx ad_bufp1 ; save pointer
 ldd #0
 ldx #ad_buf1
_ad12 addd 2,X+ ; sum all values
 cpx #ad_buf1e ; end of array ?
 bne _ad12 ; BI not
 std ad_wpres ; save water pressure
 inc ad_seq


_ad20 cmpa #2 ; 2 - read channel 2
 bne _ad30
 ldd ATDDR2 ; read result data register 2 (two bytes)
 ldx ad_bufp2 ; get pointer
 std 2,X+
 cpx #ad_buf2e ; end of array ?
 bne _ad21 ; BI not