Sick
LMS291 Configuration
Library
Olin Robotics
Blockset/Sick/Utilities
Description
Configure the LMS sensor to
transmit measurement data in the desired format. The block can also be used to save
the configuration settings permanently so that the sensor retains its
configuration even when power is cycled.
Check the tasks for which
you want to send the telegrams to the sensor. The block will send the selected
telegrams at pre-determined time-steps and record the sensor's response. The
telegrams are sent in the same order as listed in this menu. The first selected
telegram is sent at time t=0 and successive telegrams are sent with a time span
specified in the parameters dialog.
You can also send any other
telegrams via the “Send Custom Telegrams” option up to a maximum of 5
telegrams. Specify the exact telegram as a row vector in the edit box when
entering a custom telegram. The telegrams must be of data-type uint16. The
tasks listed in this dialog are the main configuration settings that you would
need to perform on an out-of-box sensor to get started with recording data at
different baud rates and data formats. However for a complete list of the
telegrams that you can send to the sensor, refer to the following manual
The Success Flag indicates
if the sensor has successfully acknowledged the receipt of a particular
telegram.
The Sick LMS291
Configuration Setup Demo from the Olin Robotics Blockset/Demos library
illustrates the use of this block. The Quick Reference Guide for Sick LMS.doc
gives detailed documentation on interfacing the Sick LMS-291 sensor to The
MathWorks tools including MATLAB and Simulnk/ Olin Robotics Blockset.
Block Parameters:
Perform Status Check: To perform status check operation on the sensor.
Change Angular Resolution: To change the angular resolution and range format.
Selecting this option enables you to choose the desired angular range and
angular resolution values that the sensor supports.
Change Measurement Units: To change the measurement units of the data. This
operation actually requires two telegrams to be sent.
Set Only Current Baud Rate as Permanent: To save the current baud-rate permanently so that the
sensor would communicate in the future at the same baud-rate even when power is
cycled. This operation requires two telegrams to be sent.
Send Custom Telegrams: To send custom telegrams to perform operations not specified
in the block menu. You can send up to a maximum of 5 telegrams. Specify the
exact telegram as a row vector in the edit box that is enabled once you check
this option and select the number of custom telegrams you want to send. Note
that the elements of the row-vector should be of decimal type and not
hexadecimal type. You need to first convert the hexadecimal values to
corresponding decimal values. For a complete list of the telegrams that you can
send to the sensor, refer to the Sick_LMS291_TelegramListing
document.
Save Current Configuration as Permanent: To save the configuration settings permanently so
that the sensor retains its configuration even when power is cycled.
Change Baud Rate: To command the sensor to communicate at a different baud rate. Selecting
this option enables you to select the desired baud rate from a list. Once this
command is sent, the sensor responds back with an acknowledgement at the
previous baud rate and thereafter only responds at the new baud rate. In order
to further receive or transmit any data, you need to first change the baud rate
of the Fastcom board to match with the baud rate of the sensor.
Fastcom Board Clock Frequency: Enter the clock generator frequency for the master
clock on the Fastcom 422/2-PCI-335 board. The default value of 14.7456 MHz
allows you to choose baud rates of 9600, 19200, 38,400. The possible baud rates
for a given clock frequency with 16x sampling rate is given by the expression
In order to communicate with
the Sick LMS291 sensor at its custom high-speed rate of 500,000, you need to
set the clock frequency to be 8MHz.
Fastcom Board IRQ Number: Enter the number of the interrupt request line for
this board. If you do not know the interrupt request line number for this
board, at the MATLAB Command Window, enter getxpcpci after connecting to the
target machine. This command displays all the PCI interfaces currently attached
to the target PC. From that display, find the instance of the board controlled
by this block. Each board uses a unique interrupt request line number.
Fastcom Board Baud Rate: Enter the baud rate you wish to communicate with the
Fastcom board. The Fastcom board the sensor would be able to communicate only
when they are at the same baud rate.
Time span between consecutive telegrams: Enter the time interval that the block should wait
between sending consecutive telegrams. The sensor may take up to 8 seconds to
respond to certain commands. It would ignore any other command that it receives
until it responds to the previous command. The default value of 5 seconds
ensures that the sensor has enough time to respond to a telegram to perform any
given operation listed in the block menu.
Sample Time: Sample time indicates the frequency (1/SampleTime) at which data is
requested from or sent to the sensor.
Outputs with example output and format
description:
1. Response: Outputs response from the sensor at each time-step. The output response
starts with either:
6hex (6 decimal) indicating
success that sensor acknowledged the command or,
15hex (21 decimal)
indicating failure that the sensor failed to acknowledge the command.
Alternate way to check if
the sensor acknowledged a command is through the Success Flag output.
The output is a 1-D vector
(data-type uint8 null terminated).
For more information on the
exact response to each telegram, refer to the Sick LMS291 TelegramListing document.
2. Success Flag: This value indicates if the sensor has successfully responded to a given
command.
0 indicates that the sensor
has successfully acknowledged the command or is idle
1 indicates that the sensor
has received a command but has not acknowledged yet
>1 indicates the sensor
has failed to acknowledge the command in the specified time span.
The command that failed to
solicit response is the one sent at the time-step when the Success Flag
parameter has a value of 1. The following figures illustrate through example
scenarios how the Success Flag variable can be used to interpret if the sensor
has acknowledged the command or not.
Scenario 1: The sensor
successfully acknowledges all the commands. As shown in the scope, 6 commands
were sent to the sensor starting from t=0 seconds with 5 seconds between
consecutive commands. At the time instant when the sensor receives the command,
the Success Flag variable becomes 1 and then drops to 0 after the sensor
acknowledges the command.
Figure 1: Typical graph for
the Success Flag variable on time axis when all the commands are acknowledged
Scenario 2: The sensor
successfully acknowledges the first command but fails to acknowledge subsequent
commands. Here you can see that at t=0, the sensor receives the command and
acknowledges it back at t=0.5 seconds. It receives the second command at t=5
seconds but does not acknowledge this command within the next five seconds when
a third command is sent at t=10 seconds.
Figure 2: Graph for the
Success Flag variable on time axis when some of the commands are not
acknowledged
Try to increase the time
span between consecutive telegrams parameter as a first troubleshooting step.
Reference
http://tourbot.mit.edu/images/7/79/LMS_Guide.pdf