Distinguish between "H" "S" "U"

i’m joining a robotic competition that required us to do different actions according to the three words “H” “S” "U"on the wall. Can i put templates of those three words and detect them?
Also, how can i send signal to arduino pro mini if a word is recognized?

If the camera is at a fixed position relative to the letter and the letters are just changing then template matching will work.

As for sending a signal, just use an I/O pin on the camera and make that go high. One pin per letter.

im trying to detect letters like H, S and U, but i tried using template matching but the camera only finds the letter when it is only in a very specific position

# Hello World Example
#
# Welcome to the OpenMV IDE! Click on the green run arrow button below to run the script!

import sensor, image, time
from pyb import UART
from image import SEARCH_EX, SEARCH_DS
ser = UART(3,115200,timeout_char=1000)

sensor.reset()                      # Reset and initialize the sensor.
sensor.set_contrast(1)
sensor.set_gainceiling(16)
sensor.set_pixformat(sensor.GRAYSCALE) # Set pixel format to RGB565 (or GRAYSCALE)
sensor.set_framesize(sensor.QQCIF)   # Set frame size to QVGA (320x240)
sensor.skip_frames(time = 2000)     # Wait for settings take effect.
template1 = image.Image("/H_Letter.pgm")
clock = time.clock()                # Create a clock object to track the FPS.

while(True):
    clock.tick()                    # Update the FPS clock.
    img = sensor.snapshot()         # Take a picture and return the image.
    harmed = img.find_template(template1, 0.70, step=4, search=SEARCH_EX) #, roi=(10, 0, 60, 60))
    if harmed:
        img.draw_rectangle(harmed,5)
        print("Detected H")
    #print(clock.fps())              # Note: OpenMV Cam runs about half as fast when connected
                                    # to the IDE. The FPS should increase once disconnected.

Yes, that is the limit of template matching.