你这个需求和回调函数没啥关系。
import sensor, image, time
import car
from pid import PID
from pyb import UART
import json
sensor.reset()
sensor.set_pixformat(sensor.RGB565)
sensor.set_framesize(sensor.QQVGA)
sensor.skip_frames(10)
sensor.set_auto_whitebal(False)
timer = pyb.Timer(4, freq=1)
uart = UART(3, 19200)
clock = time.clock()
green_threshold = (76, 96, -110, -30, 8, 66)
size_threshold = 2000
x_pid = PID(p=0.5, i=1, imax=100)
h_pid = PID(p=0.05, i=0.1, imax=50)
def find_max(blobs):
max_size=0
for blob in blobs:
if blob[2]*blob[3] > max_size:
max_blob=blob
max_size = blob[2]*blob[3]
return max_blob
def timer_callback():
print('timer_callback')
while(True):
clock.tick()
img = sensor.snapshot()
blobs = img.find_apriltags()
if blobs:
max_blob = find_max(blobs)
x_error = max_blob[6]-img.width()/2
h_error = max_blob[2]*max_blob[3]-size_threshold
print("x error: ", x_error)
img.draw_rectangle(max_blob[0:4])
img.draw_cross(int(max_blob[6]),int(max_blob[7]))
x_output=x_pid.get_pid(x_error,1)
h_output=h_pid.get_pid(h_error,1)
print("h_output",h_output)
car.run(-h_output,-h_output)
else:
car.run(50,50)
output_str=json.dumps([1])
uart.write(output_str+'\n')
timer_callback()