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readUBX.py
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#RELPOSNED and PVT
def readUBX(readbytes):
RELPOSNED = b'\x3c'
PVT =b'\x07'
POSLLH = b'\x02'
msg = dict()
j=0
while j < len(readbytes) :
i = 0
payloadlength = 0
ackPacket=[b'\xB5',b'\x62',b'\x01',b'\x00',b'\x00',b'\x00']
while i < payloadlength +8:
if j < len(readbytes) :
incoming_byte = readbytes[j]
j += 1
else :
break
if (i < 3) and (incoming_byte == ackPacket[i]):
i += 1
elif i == 3:
ackPacket[i]=incoming_byte
i += 1
elif i == 4 :
ackPacket[i]=incoming_byte
i += 1
elif i == 5 :
ackPacket[i]=incoming_byte
payloadlength = int.from_bytes(ackPacket[4]+ackPacket[5], byteorder='little',signed=False)
i += 1
elif (i > 5) :
ackPacket.append(incoming_byte)
i += 1
if checksum(ackPacket,payloadlength) :
if ackPacket[3] == RELPOSNED:
msg.update(perseNED(ackPacket))
elif ackPacket[3] == POSLLH:
msg.update(perseLLH(ackPacket))
elif ackPacket[3] == PVT:
msg.update(persePVT(ackPacket))
return msg
def checksum(ackPacket,payloadlength ):
CK_A =0
CK_B =0
for i in range(2, payloadlength+ 6):
CK_A = CK_A + int.from_bytes(ackPacket[i], byteorder='little',signed=False)
CK_B = CK_B +CK_A
CK_A &=0xff
CK_B &=0xff
if (CK_A == int.from_bytes(ackPacket[-2], byteorder='little',signed=False)) and (CK_B == int.from_bytes(ackPacket[-1], byteorder='little',signed=False)):
#print("ACK Received")
return True
else :
print("ACK Checksum Failure:")
return False
def perseNED(ackPacket):
posned = dict()
#relPosN
byteoffset =8 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posned["N"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
posned["NH"] = int.from_bytes(ackPacket[32 + 6], byteorder='little',signed=True)
#relPosE
byteoffset =12 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posned["E"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
posned["EH"] = int.from_bytes(ackPacket[33 + 6], byteorder='little',signed=True)
#relPosD
byteoffset =16 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posned["D"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
posned["DH"] = int.from_bytes(ackPacket[33 + 6], byteorder='little',signed=True) #print("D:%0.2f cm" %posned["D"] )
#Carrier solution status
flags = int.from_bytes(ackPacket[60 + 6], byteorder='little',signed=True)
posned["gnssFixOk"] = flags & (1 << 0) #gnssFixOK
posned["carrSoln"] = (flags & (0b11 <<3)) >> 3 #carrSoln0:no carrier 1:float 2:fix
#GPS time
byteoffset =4 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posned["iTow"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#relPosLength
byteoffset =20 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posned["length"] = int.from_bytes(bytevalue, byteorder='little',signed=False)
posned["lengthH"] = int.from_bytes(ackPacket[35 + 6], byteorder='little',signed=True)
#relPosHeading
byteoffset =24 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posned["heading"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
return posned
def perseLLH(ackPacket):
posllh=dict()
#PosLon
byteoffset = 4 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posllh["Lon"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#PosLat
byteoffset =8 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posllh["Lat"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#posHeight
byteoffset =12 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posllh["Height"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#Height above mean sea level
byteoffset =16 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
posllh["hMSL"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
return posllh
def persePVT(ackPacket):
pospvt=dict()
#Year
byteoffset = 4 + 6
bytevalue = ackPacket[byteoffset]
bytevalue += ackPacket[byteoffset+1]
pospvt["year"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#month day hour min sec
byteoffset =6 + 6
b=0
for key in ("month", "day", "hour", "min", "sec"):
bytevalue = ackPacket[byteoffset+b]
pospvt[key] = int.from_bytes(bytevalue, byteorder='little',signed=True)
b +=1
#PosLon
byteoffset = 24 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
pospvt["Lon"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#PosLat
byteoffset =28 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
pospvt["Lat"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#posHeight
byteoffset =32 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
pospvt["Height"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#Height above mean sea level
byteoffset =36 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
pospvt["hMSL"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#Ground Speed
byteoffset =60 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
pospvt["gSpeed"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
#Heading of motion
byteoffset =64 + 6
bytevalue = ackPacket[byteoffset]
for i in range(1,4):
bytevalue += ackPacket[byteoffset+i]
pospvt["headMot"] = int.from_bytes(bytevalue, byteorder='little',signed=True)
return pospvt
def llh2enu(msg):
basellh = (34.95379794,136.9351043,87.02)#RTK_BASE lat(deg) lon(deg) heigh(m)
rover =(msg["Lat"]*0.0000001 ,msg["Lon"]*0.0000001 ,msg["Height"]*0.001) #deg,deg,m
rover_enu = geodetic2enu(rover[0] ,rover[1] ,rover[2],basellh[0] ,basellh[1] ,basellh[2] )
msg["e"]=rover_enu[0]*100 #cm
msg["n"]=rover_enu[1]*100
msg["u"]=rover_enu[2]*100
if __name__ == "__main__":
import serial
import pprint
from pymap3d.enu import geodetic2enu
lenRELPOSNED = 6 + 64 +2
lenPOSLLH = 6 + 28 + 2
lenPVT = 6 + 92 +2
buffsize = lenRELPOSNED + lenPVT #172
#buffsize = lenRELPOSNED + lenPOSLLH #108
#buffsize = lenRELPOSNED #72
while 1:
with serial.Serial('/dev/ttyACM0', 115200, timeout=1) as ser:
readbytes =[]
for i in range(buffsize):
readbytes.append(ser.read())
ubxmsg=readUBX(readbytes)
llh2enu(ubxmsg)
pprint.pprint(ubxmsg)
"""
ubxmsg['*'] ex. northcm =ubxmsg['N']
(RELPOSNED)
N cm
E cm
D cm
NH 0.1mm
EH 0.1mm
DH 0.1mm
lengh cm
lengthH 0.1mm
heading 0.00001deg(1e-5)
carrSoln 0:no carrier 1:float 2:fix
gnssFixOk 0:no 1:ok
iTow ms GPS time of week
(PVT)
year UTC
month
day
hour
min
sec
Lon 0.0000001deg(1e-7)
Lat 0.0000001deg(1e-7)
Height mm Heigth above ellpsoid
hMSL mm Height above mean sea level
gSpeed mm/s Ground speed
headMot 0.00001deg(1e-5) Heading of motion
"""