Vernier LabPro - Manual (Page 24)

Revision Date: 08/02/02
LabPro Technical Manual 24
When using LabPro in RT mode over USB, the number of bytes transmitted back is always 16 (see above
information). For an unloaded USB bus (i.e. no other peripherals), we should have a limit of 1k samples
per second for RT mode for 1 to 6 channels active.
If you try to use RT at higher data rates, loss and corruption of data can occur. When the RT mode limit is
exceeded, the software must switch to utilize the NRT mode of LabPro. Data rate limitations change as
follows:
50K samples per second max. 1 channel active
5k samples per second max. 2 channels active
2.5k samples per second max. 3-4 channels active
2k samples per second max. 5 channels active
1k samples per second max. 6 channels active
Since the data is stored internally to LabPro prior to sending it to the host computer, the number of data
points being collected is limited to 12k samples/# of channels.
One implication of this is that the user may set up an experiment to take data from one channel at 1k
samples/second for 12 seconds. LabPro would not complete the data transfer for 18.25 seconds (12
seconds for the experiment + 6.25 seconds to data transfer over the serial port for 24000 bytes at 3840
bytes/second). Having such a delay may give the impression something is wrong. The software and the
user need to be aware of the times involved in such a situation.
Programming tips
Since the System Setup command (Command 6) must be processed while not disturbing data collection, it
is possible for additional data points to be transmitted after the Command 6 has been sent. These points
may be ignored but be aware that the receive buffer may not be empty immediately after sending this
command.
We have found that commands delimited by a carriage return character can be stacked in LabPro’s input
buffer. The input buffer can hold up to 300 characters. The benefit of stacking commands is that the
simple example
Calculator Programming
LabPro is designed to work with the TI-73, TI-82, TI-83 TI-83 Plus, TI-85, TI-86, TI-89, TI-92 and TI-92
Plus calculators. Programs are created on a TI calculator to set up specific LabPro operations, depending
on the experiment or other function that you want to perform. LabPro operations are controlled by
commands sent in the form of lists from a calculator. In the majority of cases, the data returned by LabPro
is also in the form of a list. As a rule, when a TI calculator is the host, LabPro is a passive communicator,
which must first receive a command list to provoke a response. Data is never automatically sent to the
calculator from LabPro.
Basic Communication
Below is a general example of communication between any TI calculator and LabPro:
{command number, parameter 1,…, parameter n}
→
listname
Send(listname)
Get(variable)