Xbee image transfer python

Question

Hi there i'm quite new with xBee and struggle with data transferring. My objective is to take picture with Raspberry pi wide and send it back to computer via xBee by turn that image to hexlify code. after recieving the code with python on computer i use binascii library to turn those code back to image by this code

ASCII to IMG:

import binascii
with open("file.txt", "r") as f:
    data=f.read()
data = data.strip()
data = data.replace('\n', '')
data = binascii.a2b_hex(data)
with open('image.png', 'wb') as image_file:
    image_file.write(data)

but after running that code the image is corrupted. So i start taking a look at the receiving code but I'm not sure if the code is correct, because the text file that i got has a lot of "0" in it

Receiving code:

from digi.xbee.devices import XBeeDevice
PORT = 'COM11'
BAUD = 19200
ser = XBeeDevice(PORT, BAUD)

try :
    ser.open()
    def data_receive_callback(xbee_message):
        data = xbee_message.data.decode("utf-8")
        with open("file.txt","a") as f:
            f.write(data)

    ser.add_data_received_callback(data_receive_callback)

    print("Waiting for data...\n")
    input()

finally:
    if ser is not None and ser.is_open():
        ser.close()

camera code in RPi:

from picamera import PiCamera
import serial
import binascii
ser =serial.Serial(
     port='/dev/ttyS0',
     baudrate=19200,
     parity= serial.PARITY_NONE,
     stopbits=serial.STOPBITS_ONE,
     bytesize=serial.EIGHTBITS,
     timeout=1
)
camera=PiCamera()
camera.resolution(1920,1080)
camera.capture("img.png")
with open("image.png",'rb') as f:
       content=f.read()
a=binascii.hexlify(content)
ser.write(a)
ser.close

What should I do or try to fix the code. I think its the receiving code that is a main problem.

Ps. i already try to convert image file to hexlify in both computer and Raspberry Pi and reverse it back and it still work fine.

Please show simplest possible code that captures image and sends it. Please also share file containing image - probably using Google Drive, or Dropbox if of a type you cannot post here. — Mark Setchell, Nov 27 '20 at 10:59
OK So i check the code carefully and nothing is wrong so far. But I recheck the receiving packet and I found out that the reason its not working is due to packet lost. the message i got is lost about 14 times(every packet is 114 character). is there anyway to prevent package lost in xbee??? — Papop Lekhapanyaporn, Nov 28 '20 at 11:43

score 0 · Accepted Answer · answered Nov 28 '20 at 21:14

Questions:

Why are you using an XBee instead of Wi-Fi and a standard TCP protocol like HTTP or FTP?

Work on debugging a piece of your system at a time. Instead of capturing an image on the Pi, use a small text file and see if it comes through correctly. It will be easier to see if you're dropping bytes in the middle, beginning or end of the file.

Whenever using an XBee module, be sure to enable hardware flow control (pins D6 and D7) so you don't lose any serial data. With hardware flow control, each side of the connection has the ability to signal the other side to temporarily stop sending while it processes data.

I also recommend increasing your baud rate to 115200 or even 230400 bps. That, in conjunction with the hardware flow control, will result in quicker transfers without lost bytes.

There's no need to hexlify the data -- the XBee is capable of sending 8-bit bytes when running in transparent serial mode (essentially a serial cable replacement).

That said, you don't have any way to indicate the start or end of the file -- the receiver doesn't know when the image begins or when to finish and close the file. If you continue to hexlify the data, you could send characters other than 0-9a-f to indicate that it's the start of an image or the image is complete.

Xbee image transfer python

1 Answers1