@y1gt

import sensor, image, time

from pyb import UART

import json

# For color tracking to work really well you should ideally be in a very, very,

# very, controlled enviroment where the lighting is constant...

yellow_threshold   = (79, 43, -38, 73, 29, 102)

# You may need to tweak the above settings for tracking green things...

# Select an area in the Framebuffer to copy the color settings.



sensor.reset() # Initialize the camera sensor.

sensor.set_pixformat(sensor.RGB565) # use RGB565.

sensor.set_framesize(sensor.QQVGA) # use QQVGA for speed.

sensor.skip_frames(10) # Let new settings take affect.

sensor.set_auto_whitebal(False) # turn this off.

clock = time.clock() # Tracks FPS.



uart = UART(3, 115200)

def find_max(blobs):

    max_size=0

    for blob in blobs:

        if blob.pixels() > max_size:

            max_blob=blob

            max_size = blob.pixels()

    return max_blob



while(True):

    img = sensor.snapshot() # Take a picture and return the image.



    blobs = img.find_blobs([yellow_threshold])

    if blobs:

        max_blob=find_max(blobs)

        #print('sum :', len(blobs))

        img.draw_rectangle(max_blob.rect())

        img.draw_cross(max_blob.cx(), max_blob.cy())



        output_str="[%d,%d]" % (max_blob.cx(),max_blob.cy()) #方式1

        #output_str=json.dumps([max_blob.cx(),max_blob.cy()]) #方式2

        #print('you send:',output_str)

        #uart.write(output_str+'\r\n')




    else:

        print('not found!')

    if max_blob.cx() > 70 and max_blob.cx() <85:
       if max_blob.cy() <80:
          uart.write('s')
          print('s')
       if max_blob.cy() >80:
          uart.write('t')
          print('t')
    if max_blob.cx() < 70:
       uart.write('l')
       print('l')
    if max_blob.cx() >85:
       uart.write('r')
       print('r')


![0_1558342482724_报错.png](https://fcdn.singtown.com/b9b0a8cc-b0bc-4313-b519-2e138364081c.png) 

我想把坐标转换成字符发送给STM32