problem converting pBasic to Javelin; ADC0838

Comments

• Peter Verkaik Posts: 3,956

  2006-06-02 03:43 edited 2006-06-02 03:43

  What value does clockIn get after shiftIn?
  Put
  System.out.print("clockIn=");
  System.out.println(clockIn);
  after the shiftIn() in your read() method of the· adc0838 class.
  
  regards peter
  ·
• Peter Verkaik Posts: 3,956

  2006-06-02 05:09 edited 2006-06-02 05:09

  This thread is all about the 0838.
  http://forums.parallax.com/showthread.php?p=519918
  regards peter
  ·
• verobel Posts: 81

  2006-06-02 13:11 edited 2006-06-02 13:11

  these are the values I am getting on first 2 calls to ADC0000838:
  
  muxbyte=24 clockIn=511
  muxbyte=28 clockIn=511
  lgt=-1 pot=-1
  
  in my pBasic program the equivalent result for clockIn was ADCresult = 154
  you might have noticed some shifts I did on muxbyte << 11
  and clockIn >> 8 (the output above was before I did the shift)
  ..these appear to be required since javelin is using 16 bit words and pBasic uses 8 bit words
  
  john
• Peter Verkaik Posts: 3,956

  2006-06-02 13:55 edited 2006-06-02 13:55

  In that other thread they talked about an extra bit at the start (which leads to 511,
  which cannot be with 8bit data) that must be stripped off.
  I think the right code is
  ··· CPU.writePin(enablePin,false);· //enable, triggers at falling edge
  ··· CPU.shiftOut(dataPin, clockPin, nBits, CPU.SHIFT_MSB, muxbyte <<11);
  ··· clockIn = CPU.shiftIn(dataPin,clockPin,readSize,CPU.POST_CLOCK_MSB);
  ··· clockIn = clockIn&0xFF; //strip off extra bit
  ··· CPU.writePin(enablePin,true);··· // disable, setup for next trigger
  
  regards peter
• verobel Posts: 81

  2006-06-02 13:59 edited 2006-06-02 13:59

  I looked at the 2004 thread on ADC0838 and it is all pBasic.. but there was an interesting discussion on the 9th bit.. and filtering it out with & $00FF .. or & 0x00FF (for java), which I have tried.. on doing this the clockIn value is 255 or %11111111 ... expecting value more like %10011000
  
  I've double checked the pins
  There is the CPU.writePin(clockPin, false); // to give positive pulses
  There is the hgh to low trigger
  CPU.writePin(enablePin,true);
  CPU.writePin(enablePin,false);
  
  To my mind it is likely one of the following is wrong orr behaving different to pBasic:
  
  on CPU.shiftOut(dataPin, clockPin, nBits, CPU.SHIFT_MSB, muxbyte <<11);
  CPU.SHIFT_MSB // MSB sent first, nBits=5
  muxbyte << 11 // I want top 5 bits shifted out, so I shift them to the top first
  
  on CPU.shiftIn(dataPin,clockPin,readSize,CPU.POST_CLOCK_MSB);
  CPU.POST_CLOCK_MSB // post clock sampling and MSB-first transmission
  
  john
• Peter Verkaik Posts: 3,956

  2006-06-02 14:02 edited 2006-06-02 14:02

  You should also change
  ····· lgt = lgt*100/255-1;·· // -1 added to avoid field overflow at 255
  ····· pot = adc.read(1);···· // read pot from chn 1
  ····· pot = pot*100/255-1;
  to
  ····· lgt = (lgt*100)/255;
  ····· pot = adc.read(1);···· // read pot from chn 1
  ····· pot = (pot*100)/255;
  
  I think the IDE is smart enough to recognize that mathematically
  ····· lgt = lgt*100/255-1 equals lgt=lgt*constant-1
  where constant is·100/255
  But due to integer math, 100/255 = 0, hence lgt=-1 using the current formula.
  
  It is always wise to use brackets in your formula. That way you have full control
  on how calculation is done.
  
  regards peter
• Peter Verkaik Posts: 3,956

  2006-06-02 14:06 edited 2006-06-02 14:06

  The adc0831 class uses
  ··· CPU.writePin(enablePin,false);
  ··· clockIn = CPU.shiftIn(dataPin,clockPin,readSize,CPU.POST_CLOCK_MSB);
  ··· CPU.writePin(enablePin,true);
  ··· CPU.delay(100);
  ··· lastRaw = clockIn;······························ // raw is protected
  
  (there is no 9th bit there)
  so I guess the shift modes are correct.
  
  regards peter
• Peter Verkaik Posts: 3,956

  2006-06-02 14:16 edited 2006-06-02 14:16

  Also, initialize CS pin high in the 0838 constructor.
  Then in read method, make CS low, then read data, then make CS high again.
  
  That is the order used in the BS2 program from that other thread.
  
  Read_0838:
  · LOW CS
  · ' setup mux bits for single-ended mode
  · LOOKUP chan, [noparse][[/noparse]%1000, %1100, %1001, %1101,
  ··············· %1010, %1110, %1011, %1111], mux
  
  · SHIFTOUT Dio, CLk, MSBFIRST, [noparse][[/noparse]1\1, mux\4]···· ' send start, mux
  · SHIFTIN Dio, Clk, MSBPOST, [noparse][[/noparse]adc(chan)\9]····· ' read selected input into byte·variable
  · HIGH CS
  
  · RETURN
  
  regards peter
• verobel Posts: 81

  2006-06-02 17:38 edited 2006-06-02 17:38

  hi Peter...thanks for all the feedback
  
  I have incorporated all your suggestions and get clockIn=255 ..want values in range approx: 30->230·.. so it still is not working as far as I can tell.
  
  debug shows:
  muxbyte=24 dataPin=6 clockPin=0 enablePin=5 readSize=9 clockIn=255
  
  latest programs attached
  I plugged by BS2pe back in and it still works..
  
  john

  java

  java

  Multi5.java

  3K

  java

  java

  ADC0838.java

  3K

  Multi5.java 3.3K

  ADC0838.java 2.6K