# UART Control
#
# This example shows how to use the serial port on your OpenMV Cam. Attach pin
# P4 to the serial input of a serial LCD screen to see "Hello World!" printed
# on the serial LCD display.

import time
from pyb import UART
import sensor, image, time
from pyb import UART
import json
import pyb
threshold_index = 0 # 0 for red, 1 for green, 2 for blue

thresholds = [(5, 100, 30, 127, 0, 80), # generic_red_thresholds
              (5, 100, -127, -20, 0, 80), # generic_green_thresholds
              (5, 100, -20, 30, -127, -20)] # generic_blue_thresholds
led = pyb.LED(3)

sensor.reset()
sensor.set_pixformat(sensor.RGB565) # grayscale is faster
sensor.set_framesize(sensor.QQVGA)
sensor.skip_frames(time = 2000)
clock = time.clock()

# Always pass UART 3 for the UART number for your OpenMV Cam.
# The second argument is the UART baud rate. For a more advanced UART control
# example see the BLE-Shield driver.
uart = UART(3, 115200)

sensor.set_auto_gain(False) # must be turned off for color tracking
sensor.set_auto_whitebal(False) # must be turned off for color tracking

uart = UART(3, 115200)
flag = 0
cnt = 0
x = 0
y = 0

while(True):
    #output = "%d"%(3)
    #uart.write(output)
    clock.tick()

    if uart.any():
      a = uart.readline().decode().strip()
      print(a)
      flag = int(a)
      print(flag)
    if flag == 1:
      img = sensor.snapshot().lens_corr(1.8)

   # uart.write("Hello World!\r")
   # time.sleep(100)
发送的数据为 1 或者 2
单片机端代码
         sprintf(printbuff1, "1\r\n");                  //显示
         uart_putstr(UART1,printbuff1);

会出现图中的错误，怎么解决呢