def __init__(self, com_port, baudrate, hasViz):
rospy.init_node("rvr_lidar")
self.pub = rospy.Publisher("/lidar", LidarPoint)
self.lidarData = [LidarPoint() for i in range(360)]
self.init_level = 0
self.index = 0
self.serial = serial.Serial(com_port, baudrate)
self.hasViz = hasViz
if self.hasViz:
self.viz = LidarViz(8000)
class Lidar:
def __init__(self, com_port, baudrate, hasViz):
rospy.init_node("rvr_lidar")
self.pub = rospy.Publisher("/lidar", LidarPoint)
self.lidarData = [LidarPoint() for i in range(360)]
self.init_level = 0
self.index = 0
self.serial = serial.Serial(com_port, baudrate)
self.hasViz = hasViz
if self.hasViz:
self.viz = LidarViz(8000)
def checksum(self, data):
"""
Compute and return the checksum as an int.
data -- list of 20 bytes (as ints), in the order they arrived.
"""
# group the data by word, little-endian
data_list = []
for t in range(10):
data_list.append(data[2*t] + (data[2*t+1] << 8))
# compute the checksum on 32 bits
chk32 = 0
for d in data_list:
chk32 = (chk32 << 1) + d
# return a value wrapped around on 15 bites, and truncated to still fit into 15 bits
checksum = (chk32 & 0x7FFF) + (chk32 >> 15) # wrap around to fit
checksum = checksum & 0x7FFF # truncate to 15 bits
return int(checksum)
def compute_speed(self, data):
return float(data[0] | (data[1] << 8)) / 64.0
def update_position(self, angle, data):
# unpack data
x0 = data[0]
x1 = data[1]
x2 = data[2]
x3 = data[3]
dist_mm = x0 | ((x1 & 0x3f) << 8) # distance is coded on 13 bits ? 14 bits ?
quality = x2 | (x3 << 8) # quality is on 16 bits
self.lidarData[angle].dist_mm = dist_mm
self.lidarData[angle].quality = quality
point = LidarPoint()
point.angle = angle
point.dist_mm = dist_mm
point.quality = quality
self.pub.publish(point)
if self.hasViz:
self.viz.redraw(x1, angle, dist_mm, quality)
def run(self):
while not rospy.is_shutdown():
try:
rospy.sleep(0.00001)
if self.hasViz:
self.viz.checkKeys()
if self.init_level == 0:
byte = ord(self.serial.read(1))
# start byte
if byte == 0xFA:
self.init_level = 1
else:
self.init_level = 0
elif self.init_level == 1:
# position index
byte = ord(self.serial.read(1))
if byte >= 0xA0 and byte <= 0xF9:
self.index = byte - 0xA0
self.init_level = 2
elif byte != 0xFA:
self.init_level = 0
elif self.init_level == 2:
# speed
b_speed = [ord(b) for b in self.serial.read(2)]
# data
b_data0 = [ord(b) for b in self.serial.read(4)]
b_data1 = [ord(b) for b in self.serial.read(4)]
b_data2 = [ord(b) for b in self.serial.read(4)]
b_data3 = [ord(b) for b in self.serial.read(4)]
# for the checksum, we need all the data of the packet...
# this could be collected in a more elegant fashion...
all_data = [0xFA, self.index+0xA0] + b_speed + b_data0 + b_data1 + b_data2 + b_data3
# checksum
b_checksum = [ord(b) for b in self.serial.read(2)]
incoming_checksum = int(b_checksum[0]) + (int(b_checksum[1]) << 8)
# verify that the received checksum is equal to the one computed from the data
if self.checksum(all_data) == incoming_checksum:
speed_rpm = self.compute_speed(b_speed)
if self.hasViz:
self.viz.update_speed(int(speed_rpm))
self.update_position(self.index * 4 + 0, b_data0)
self.update_position(self.index * 4 + 1, b_data1)
self.update_position(self.index * 4 + 2, b_data2)
self.update_position(self.index * 4 + 3, b_data3)
else:
rospy.logwarn("checksum mismatch")
null_data = [0, 0x80, 0, 0]
self.update_position(self.index * 4 + 0, null_data)
self.update_position(self.index * 4 + 1, null_data)
self.update_position(self.index * 4 + 2, null_data)
self.update_position(self.index * 4 + 3, null_data)
self.init_level = 0
except Exception as e:
rospy.logerr(e)