SHIFTIN Example

NOTE: The example below is written for the BS2 and will run on any of the BS2-family modules. Modify the $STAMP directive (as required) before downloading to the BS2e, BS2sx, BS2p, BS2pe, or BS2px.

' SHIFTIN.BS2
' This program uses the SHIFTIN instruction to interface with the ADC0831
' 8-bit analog-to-digital converter from National Semiconductor.

' {$STAMP BS2}
' {$PBASIC 2.5}

CS              PIN     0                       ' chip select
AData           PIN     1                       ' data pin
Clk             PIN     2                       ' clock pin

adcRes          VAR     Byte                    ' ADC result


Setup:
  HIGH CS                                       ' deselect ADC

' In the loop below, just three lines of code are required to read the
' ADC0831. The SHIFTIN command does most of the work.  The mode argument in
' the SHIFTIN command specifies MSB or LSB-first and whether to sample data
' before or after the clock. In this case, we chose MSB-first, post-clock.
' The ADC0831 precedes its data output with a dummy bit, which we take care
' of by specifying 9 bits of data instead of 8.

Main:
  DO
    LOW CS                                      ' activate the ADC0831
    SHIFTIN AData, Clk, MSBPOST, [adcRes\9]     ' shift in the data
    HIGH CS                                     ' deactivate ADC0831
    DEBUG ? adcRes                              ' show conversion result
    PAUSE 1000                                  ' wait one second
  LOOP                                          ' repeat
  END