Hi all,

I have been trying to send a stream of data from the OpenMV which I am using for image processing and then output numbers to my Pi in order to guide a robot I am building for a project.

I am able to receive the data and read it when using the screen function on the Pi, however I seem to only be receiving unusable values when I try to read it with my python script.

I am unsure if this is a problem with how the data is being sent from the camera or if it is a problem with how the Pi is reading it.

I am using an OpenMV M7 and a Raspberry Pi 3 B+ running Ubuntu Mate.

The OpenMV code is some linear regression code from the OpenMV blog that I have made some minor changes to.

Code for the OpenMV camera:

```
BINARY_VIEW = True
GRAYSCALE_THRESHOLD = (0, 230) #230
MAG_THRESHOLD = 4
THETA_GAIN = 40.0
RHO_GAIN = -1.0
P_GAIN = 0.7
I_GAIN = 0.0
I_MIN = -0.0
I_MAX = 0.0
D_GAIN = 0.1
import sensor, image, time, math, pyb
usb = pyb.USB_VCP()
sensor.reset()
sensor.set_pixformat(sensor.GRAYSCALE)
sensor.set_framesize(sensor.QQVGA)
#sensor.set_vflip(True)
#sensor.set_hmirror(True)
sensor.skip_frames(time = 2000)
clock = time.clock()
def line_to_theta_and_rho(line):
if line.rho() < 0:
if line.theta() < 90:
return (math.sin(math.radians(line.theta())),
math.cos(math.radians(line.theta() + 180)) * -line.rho())
else:
return (math.sin(math.radians(line.theta() - 180)),
math.cos(math.radians(line.theta() + 180)) * -line.rho())
else:
if line.theta() < 90:
if line.theta() < 45:
return (math.sin(math.radians(180 - line.theta())),
math.cos(math.radians(line.theta())) * line.rho())
else:
return (math.sin(math.radians(line.theta() - 180)),
math.cos(math.radians(line.theta())) * line.rho())
else:
return (math.sin(math.radians(180 - line.theta())),
math.cos(math.radians(line.theta())) * line.rho())
def line_to_theta_and_rho_error(line, img):
t, r = line_to_theta_and_rho(line)
return (t, r - (img.width() // 2))
old_result = 0
old_time = pyb.millis()
i_output = 0
output = 90
operation = ""
while True:
out_tot = 0
out_avg = 0
for x in range(3):
clock.tick()
img = sensor.snapshot().histeq()
if BINARY_VIEW:
img.binary([GRAYSCALE_THRESHOLD])
img.erode(1)
line = img.get_regression([(0, 0)], robust=True)
print_string = ""
if line and (line.magnitude() >= MAG_THRESHOLD):
img.draw_line(line.line(), color=127)
t, r = line_to_theta_and_rho_error(line, img)
new_result = (t * THETA_GAIN) + (r * RHO_GAIN)
delta_result = new_result - old_result
old_result = new_result
new_time = pyb.millis()
delta_time = new_time - old_time
old_time = new_time
p_output = new_result
i_output = max(min(i_output + new_result, I_MAX), I_MIN)
d_output = (delta_result * 1000) / delta_time
pid_output = (P_GAIN * p_output) + (I_GAIN * i_output) + (D_GAIN * d_output)
output = 90 + max(min(int(pid_output), 90), -90)
print_string = "Line Ok - turn %d - line t: %d, r: %d" % (output, line.theta(), line.rho())
else:
print_string = "Line Lost - turn %d" % output
out_tot += output
out_avg = out_tot // 3
usb.send(str(out_avg), timeout=100)
```

Code for the Raspberry Pi:

```
#!/usr/bin/python
import serial
ser = serial.Serial()
ser.port = "/dev/ttyACM0"
ser.baudrate = 115200
ser.timeout = 100
ser.open()
while True:
if ser.isOpen():
value = ser.read()
print(value)
```