Example Script "bmp180Press100Hz.py - can only concatenate str -

[Connor Esterwood]

When running the script I get the following error

Shimmer + Python\shimmer3-master\LogAndStream\python_scripts\bmp180Press100Hz.py", line 39, in <module> ddata += ser.read(framesize) TypeError: can only concatenate str (not "bytes") to str

I'm not sure how to fix this but it seems like an issue with the way that data is manged here?

Here is my whole code for reference:

#!/usr/bin/python
#encoding=cp850
#the encoding must be set to match the encoding being used by the terminal this
#script is being run in (due to printing the � symbol)
#this can be found by reading sys.stdout.encoding

import sys, struct, serial

def wait_for_ack():
   ddata = ""
   ack = struct.pack('B', 0xff)
   while ddata != ack:
      ddata = ser.read(1)
   return

if len(sys.argv) < 2:
   print("no device specified")
   print("You need to specify the serial port of the device you wish to connect to")
   print("example:")
   print("   bmp180Press100Hz.py Com12")
   print("or")
   print("   bmp180Press100Hz.py /dev/rfcomm0")
else:
   ser = serial.Serial("COM5", 115200)
   ser.flushInput()
# read the calibration coefficients
   ser.write(struct.pack('B', 0x59))
   wait_for_ack()

   ddata = ""
   calibcoeffsresponse = struct.pack('B', 0x58)
   while ddata != calibcoeffsresponse:
      ddata = ser.read(1)

   ddata = ""
   numbytes = 0
   framesize = 22
   while numbytes < framesize:
      ddata += ser.read(framesize)
      numbytes = len(ddata)
   data = ddata[0:framesize]

   (AC1, AC2, AC3, AC4, AC5, AC6, B1, B2, MB, MC, MD) = struct.unpack('>hhhHHHhhhhh', data)
   print ("Calibration coefficients:\n\tAC1: %d\n\tAC2: %d\n\tAC3: %d\n\tAC4: %d\n\tAC5: %d\n\tAC6: %d\n\t B1: %d\n\t B2: %d\n\t MB: %d\n\t MC: %d\n\t MD: %d\n" % (AC1, AC2, AC3, AC4, AC5, AC6, B1, B2, MB, MC, MD))

# send the set sensors command
   ser.write(struct.pack('BBBB', 0x08, 0x00, 0x00, 0x04))  #bmp180 press
   wait_for_ack()
# set OSS value (0-3)
   OSS = 0
   ser.write(struct.pack('BB', 0x52, OSS))
   wait_for_ack()
# send the set sampling rate command
   ser.write(struct.pack('BBB', 0x05, 0x40, 0x01)) #102.4Hz (320 (0x0140)). Has to be done like this for alignment reasons
#   ser.write(struct.pack('BBB', 0x05, 0x80, 0x0C)) #10.24Hz (3200 (0x0C80)). Has to be done like this for alignment reasons
   wait_for_ack()
# send start streaming command
   ser.write(struct.pack('B', 0x07))
   wait_for_ack()

# read incoming data
   ddata = ""
   numbytes = 0
   framesize = 9 # 1byte packet type + 3byte timestamp + 2byte BMP180 Temperature + 3byte BMP180 Press

   print ("Packet Type,Timestamp,Uncompensated Temperature,Temperature (�C),Uncompensated Pressure,Pressure (Pa)")
   try:
      while True:
         while numbytes < framesize:
            ddata += ser.read(framesize)
            numbytes = len(ddata)
         
         data = ddata[0:framesize]
         ddata = ddata[framesize:]
         numbytes = len(ddata)

         (packettype,) = struct.unpack('B', data[0:1])
         (timestamp0, timestamp1, timestamp2) = struct.unpack('BBB', data[1:4])
         timestamp = timestamp0 + (timestamp1 << 8) + (timestamp2 << 16)
         
         (UT,) = struct.unpack('>H', data[4:6])
         (msb, lsb, xlsb) =struct.unpack('BBB', data[6:framesize])
#         print "msb: 0x%02x\tlsb: 0x%02x\txlsb: 0x%02x" % (msb, lsb, xlsb)
         UP = ((msb<<16) + (lsb<<8) + xlsb)>>(8-OSS)
         
#*******************************************************************************************************************************
# use the test values in the BMP180 datasheet (figure 4)
         '''
         AC1 = 408
         AC2 = -72
         AC3 = -14383
         AC4 = 32741
         AC5 = 32757
         AC6 = 23153
         B1 = 6190
         B2 = 4
         MB = -32767
         MC = -8711
         MD = 2868

         OSS = 0

         UT = 27898
         UP = 23843
         '''
#*******************************************************************************************************************************

         X1 = (UT - AC6) * AC5 / 32768
         X2 = MC * 2048 / (X1 + MD)
         B5 = X1 + X2
         T = (B5 + 8) / 16

         B6 = B5 - 4000
         X1 = (B2 * (B6 * B6 / 4096)) / 2048
         X2 = AC2 * B6 / 2048
         X3 = X1 + X2
         B3 = (((AC1 * 4 + X3) << OSS) + 2) / 4
         X1 = AC3 * B6 / 8192
         X2 = (B1 * (B6 * B6 / 4096)) / 65536
         X3 = ((X1 + X2) + 2) / 4
         B4 = AC4 * (X3 + 32768) / 32768
         B7 = (UP - B3) * (50000 >> OSS)
         if B7 < 0x80000000: 
            p = (B7 * 2) / B4
         else:
            p = (B7 / B4) * 2
         X1 = (int((p / 256.0) * (p / 256.0)) * 3038) / 65536
         X2 = (-7357 * p) / 65536
         p += (X1 + X2 + 3791) / 16

#         print "Temperature = %.1f�C, Pressure = %dPa"  % (T/10.0, p)
         print ("0x%02x,%5d,\t%4d, %0.1f,\t%4d, %d" % (packettype, timestamp, UT, T/10.0, UP, p))

   except KeyboardInterrupt:
#send stop streaming command
      ser.write(struct.pack('B', 0x20))
      wait_for_ack()
#close serial port
      ser.close()
      print
      print ("All done")

[Mark Nolan]

@ConnorEsterwood do you know what version of Python you are using? We are trying to repeat using Python 2.7 and it's not showing the error.