TLC1543 ADC not getting data

dev/null · 2009-07-17 23:38

Hi

I am trying to get an ADC to work (TLC1543). The signal is coming from a small preamplifier with a microphone on it. The problem is that I get only zero bits out. It's 10-bit so should be able to pick up the slightest of voltages.

Datasheet attached. I wired it like this:

I am trying to use "mode 1" from the datasheet. Here is the code:

Init:
  addr = %0000 ' Select input A0

ReadADC:
  HIGH cs ' Start measure
  PAUSE 2
  LOW cs ' Activate TLC1543
  PAUSE 1
  SHIFTOUT dat, clk, MSBFIRST, [noparse][[/noparse]add] ' Send address
  SHIFTIN dat, clk, MSBPRE, [noparse][[/noparse]bits\10]
  DEBUG BIN10 bits,CR
  PAUSE 1000
  GOTO ReadADC

Thanks for any help.

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phil kenny · 2009-07-18 14:17

Have you tried adding a short PAUSE between the SHIFTOUT and
SHIFTIN commands?

The ADC needs 21 usec to complete the conversion.

phil

dev/null · 2009-07-18 19:09

The ADC will send the result of the previous conversion while you it is converting the next one, so you don't have to do that.
I found some code that worked for a 12-bit ADC, and it works for this one! The following code works for the 1543 (it's a miracle!):

ADch VAR Nib ' selects AD external channel 0-10
result VAR Word ' result, 12 bit A/D conversion

demo: ' to show off the subroutine below.
'DIRS=$FFFF ' makes all Stamp pins outputs to start
'OUTS=$1000 ' makes all pins except ADC chip select low to start
LOW ADcs
DO
  GOSUB ADwake ' makes a dummy conversion to initialize converter
  FOR ADch =0 TO 10 ' specify one of 11 input channels
    GOSUB ADread ' get millivolt data from that channel
    result = 14464 ** result + result ' convert count to millivolts.
    DEBUG DEC ADch,": ",DEC result,REP 32\5,CR ' display, use extra spaces to clear garbage
  NEXT
  GOSUB ADsleep
  'NAP 1
  DEBUG HOME ' repeat the demo
LOOP

ADread: ' entry point to give result as count from 0 to 4095
 LOW ADcs ' select chip
 SHIFTOUT sdo,sclk,MSBFIRST,[noparse][[/noparse]ADch<<8\12] ' mode, left justify ADch
 SHIFTIN sdi,sclk,MSBPRE,[noparse][[/noparse]result\12] ' get result, 12 bits
 HIGH ADcs ' deselect chip
RETURN

ADsleep: ' entry point to put TLC2543 to sleep
 LOW ADcs ' select chip
 SHIFTOUT sdo,sclk,MSBFIRST,[noparse][[/noparse]$e\4] ' command=$e
 HIGH ADcs ' deselect chip
 LOW sdi ' keep this pin from floating in sleep
RETURN

ADwake:
 ADch=$b
 GOTO ADread

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Don't worry. Be happy

TLC1543 ADC not getting data

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