For about $25 you can make a simple A/D converter that plugs into the parrallel port of your BEE and use a simple BASIC programme to read the 8 bit data words into memory and display them on the screen.
You can then modify the programme to do such things as sounding a tone if a certain value is exceeded or fallen short of ,time the onset of an event from the start of Data Logging . You can also do calculations on the stored data values .e.g. calculate average values or area under a curve.
The A/D uses a National Semiconductor 0804 chip in the free running configuration.(updates every 100 micro secs.) It is powered from the BEE's 5 volt supply which is available at pins 8(5v) and 1(Gnd.) of the parallel port.
The other hardware required consists of a circuit board , a 15 way Cannon type connector ,a cap. and a resistor.
To start the 0804 reading just remove from the I/O port andreplug it in with the BEE switched on.(or momentarily ground pins 3&5).
The BASIC programme uses the IN(0) command to read the data word at the PIO port.As this is used in a loop to control the total no of reads and also allow for scaling to keep the screen display shorter than 512 horizontal positions the time between reads depends on the input conditions and is of the order of 1/20 TO 1/30 th. of a second.
To have strict control of the timing a machine language routine must be used (this also allows a much smaller time interville to be used.
The Data is stored as a subscripted variable D(n).
