Vernier LabPro - Manual (Page 6)

Revision Date: 08/02/02
LabPro Technical Manual 6
be used at a time. The GraphLink port is used almost exclusively with a TI Graphing calculator while the
USB and RS-232 ports are used with a computer.
LabPro has six interface ports for data collection. The ports labeled CH1 through CH4 are used to collect
analog data from sensors such as temperature, pH, force etc. The ports labeled DIG/SONIC1 and
DIG/SONIC2 are used to collect digital data from such sensors as photogates, motion detectors, radiation
monitors, and rotary motion sensors. LabPro may also be used to control 8 digital output lines and one
analog output line (see connector information for pin assignments).
Programming LabPro
Programming of LabPro consists of sending a series of commands to configure the desired operation.
There are a few dozen commands to control LabPro and request its status. Within a program, different
commands are used to set up the number of active channels, rate of data collection, quantity of data
collected, and how data is to be processed. Since the command set is rather extensive, this manual will
detail some building blocks to illustrate how the commands are used within the context of a program.
Each command consists of a series of numbers that are sent to the LabPro. For example, the data rate for
data collection is set with a Command 3, like this:
3,1,1,0
If you are using a TI calculator to write the programs, you typically store the data in a list and then send it
to LabPro. If you are using a computer to control LabPro, you send these commands to LabPro using
either the serial or USB port. Refer to the Calculator Programming and Computer Programming sections
of this manual.
While error checking and command parsing are built into LabPro, it is preferred that the program use the
commands as defined. That is to say, do not terminate commands in midstream. Complete requests for
data by retrieving requested data prior to sending a new command. In general, attempts to keep a
synchronous command/response sequence intact will add to the reliability of the design.
Program Structure
Programs for data collection with LabPro usually follow this basic pattern:
•
Initialize LabPro
•
Activate Channels from which data is to be collected.
•
Define and Initiate data collection mode.
•
Retrieve data from LabPro.
Initialization
Initialization takes place whenever the data collection settings need to be changed. The command used to
search for an attached LabPro is Command 7 (status command). Besides indicating if a LabPro is attached,
it provides valuable information regarding current status of the attached LabPro unit. Upon launch of the
program it may be particularly important to search for LabPro by only using a Command 7. This is due to
the fact that there may be data in the buffer from a previous experiment that needs to be accessed prior to
reset and setup commands being sent.