SERIAL PROTOCOL
USER’S MANUAL
SWEEP
V1.0
8
Copyright ©2014-2017 Scanse LLC - www.scanse.io
•
Initiates scanning
•
Sensor responds with header containing status.
•
Sensor begins sending constant stream of Data Block receipts, each containing a single sensor readings. This
stream continues indefinitely until the host sends a DX command.
(HOST -> SENSOR)
D
S
LF
(SENSOR -> HOST)
Header response
D
S
Status (2 bytes)
SUM (1 byte)
LF
The DS command is not guaranteed to succeed. There are a few conditions where it will fail. In the event of a
failure, the two status bytes are used to communicate the failure.
Status Code (2 byte ASCII code):
•
‘00’: Successfully processed command. Data acquisition effectively initiated
•
‘12’: Failed
to process command. Motor speed has not yet stabilized. Data acquisition NOT initiated. Wait
until motor speed has stabilized before trying again.
•
‘13’: Failed to process command. Motor is currently stationary (0Hz). Data acquisition NOT initiated.
Adjust motor speed before trying again.
(SENSOR -> HOST)
Data Block (7 bytes) Data Block
Sync/Error
(1 byte)
Azimuth - degrees(float)
(2 bytes)
Distance - cm(int)
(2 bytes)
Signal Strength
(1 byte)
Checksum
(1 byte)
Data Block Structure:
The
Data Block
receipt is 7 bytes long and contains all the information about a single sensor reading.
•
Sync/Error Byte:
The sync/error byte is multi-purpose, and encodes information about the rotation of the
Sweep sensor, as well as any error information. Consider the individuals bits:
e6
e5
e4
e3
e2
e1
e0
sync
o
Sync bit
: least significant bit (LSB) which carries the sync value. A value of
1
indicates that this
Data Block is the first acquired sensor reading since the sensor passed the 0 degree mark. Value
of
0
indicates all other measurement packets.
o
Error bits
: 7 most significant bits (e0-6) are reserved for error encoding. The bit
e0
indicates a
communication error with the LiDAR module with the value
1
. Bits
e1:6
are reserved for future
use.
•
Azimuth:
Angle that ranging was recorded at (in degrees). Azimuth is a float value, transmitted as a 16 bit
int. This needs to be converted from 16bit int to float. Use instructions in the Appendix. Note: the lower
order byte is received first, higher order byte is received second.
•
Distance:
Distance of range measurement (in cm). Distance is a 16 bit integer value. Note: the lower order
byte is received first, higher order byte is received second. Use instructions in the Appendix.
•
Signal strength :
Signal strength of current ranging measurement. Larger is better. 8-bit unsigned int,
range: 0-255
•
Checksum:
Calculated by adding the 6 bytes of data then dividing by 255 and keeping the remainder.
(Sum of bytes 0-5) % 255 ... Use the instructions in the Appendix.
