Sending changing values over Serial to Arduino

Hi there,
currently I’m working on a robotics project where I want to detect colored Blocks and send the angle of the block to my Teensy. The Angle is also always changing. But on Arduino are no values which I can read out he just tells me there’s nothing. I also already checked the cabeling. But I’m quite new in phyton so it could also be a programming issue.
Thanks for help, Theo.

Here’s my code in OpenMV IDE:

# This work is licensed under the MIT license.
# Copyright (c) 2013-2023 OpenMV LLC. All rights reserved.
# Multi Color Blob Tracking Example
# This example shows off multi color blob tracking using the OpenMV Cam.

import sensor
import time
import math

import time
from pyb import UART

# Color Tracking Thresholds (L Min, L Max, A Min, A Max, B Min, B Max)
# The below thresholds track in general red/green things. You may wish to tune them...
thresholds = [
(50, 60, 10, 127, 21, 85),  # generic_red_thresholds
]  # generic_blue_thresholds
# You may pass up to 16 thresholds above. However, it's not really possible to segment any
# scene with 16 thresholds before color thresholds start to overlap heavily.

uart = UART(3, 19200)

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

# Only blobs that with more pixels than "pixel_threshold" and more area than "area_threshold" are
# returned by "find_blobs" below. Change "pixels_threshold" and "area_threshold" if you change the
# camera resolution. Don't set "merge=True" because that will merge blobs which we don't want here.
data = 6
while True:
    img = sensor.snapshot()
    for blob in img.find_blobs(thresholds, pixels_threshold=200, area_threshold=200):
        # These values depend on the blob not being circular - otherwise they will be shaky.
        if blob.elongation() > 0.5:
            img.draw_edges(blob.min_corners(), color=(255, 0, 0))
            img.draw_line(blob.major_axis_line(), color=(0, 255, 0))
            img.draw_line(blob.minor_axis_line(), color=(0, 0, 255))
        # These values are stable all the time.
        # Note - the blob rotation is unique to 0-180 only.
            [(,, int(math.degrees(blob.rotation())))], size=20

        XStandort = 240;
        YStandort = 0;

        XTor =
        YTor =

        XEnde = XTor - XStandort
        YEnde = YTor - YStandort

        TorRichtung = (((math.atan2(XEnde, YEnde)) * 180) / math.pi) + 50

    # UART 3, and baudrate.

And here’s my Arduino code running on my Teensy 4.1:

char Tor;

void setup() {
  Serial.println("Starting ");


void loop() {
    Tor =;
    Tor = 1;

The code looks right to me.

uart = UART(3, 19200)

That line should have created and initialized the uart. Documentation specifies that by adding the second baudrate parameter uart should also be initialized. I would split that into two statements though, creating the object and then running uart.init() just for readability and making sure that this isn’t your issue.


This looks right to me.

Did you remember to connect the camera RX to board TX and board TX to camera RX?

Also, UART(3) creates the object on P4 and P5 for the H7 if that’s what you’re using, so make sure you didn’t mistakenly connect to P1 and P0.

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