LCD flickers with ghost images

OpenMV Pure Thermal
1

Hi,
Just getting started with an OpeMV PT, without a Lepton attached (I don’t have one).
I’ve modified the main.py found in the 34MB drive which appears after plugging in and powering on the board to get rid of anything related to the Lepton.

The code runs (from the IDE, not as a standalone main.py) but the image on the LCD flickers with superimposition of the main image on itself (the 2nd image is the ghost), shifted at random values along the width of the display (the “ghost” image jumps around):

IMG_20220424_215101
IMG_20220424_2151011280×720 169 KB

My code:

import sensor, image, time, lcd, math, pyb

from machine import I2C
from vl53l1x import VL53L1X

# Color Tracking Thresholds (Grayscale Min, Grayscale Max)
threshold_list = [(200, 255)]

def main():

    i2c = I2C(2)
    distance = VL53L1X(i2c)

    sensor.reset()
    sensor.set_pixformat(sensor.RGB565)
    sensor.set_framesize(sensor.VGA)
    time.sleep_ms(50)

    lcd.init(lcd.LCD_DISPLAY, framesize=lcd.FWVGA, refresh=30)
    #lcd.init(lcd.LCD_DISPLAY_WITH_HDMI, framesize=lcd.FWVGA, refresh=60)
    #lcd.init(lcd.LCD_DISPLAY_WITH_HDMI, framesize=lcd.VGA, refresh=60)

    alpha_pal = image.Image(256, 1, sensor.GRAYSCALE)
    for i in range(256): alpha_pal[i] = int(math.pow((i / 255), 2) * 255)


    while True:
        img = sensor.snapshot()
        img.draw_string(4, 54, 'Distance: %d mm' % distance.read(), color = (255, 255, 255), mono_space = False, scale = 2)

        lcd.display(img, x_size = lcd.width(),y_size = lcd.height(), hint = image.BILINEAR)
        #lcd.display(img,  hint = image.BILINEAR)


try:
    main()
except OSError:

    # I2C Bus may be stuck
    p = pyb.Pin('P4', pyb.Pin.OUT_OD)
    for i in range(20000):
        p.value(not p.value())

    pyb.hard_reset()

Why is it so?

Ludo

2

I just received a Pure Thermal board and had a possibly related issue. In my case the image was broken up and jumping around vertically. I believe it was caused by a bad connection between the display FPC and the Pure Thermal board - opening that FPC connector, removing and re-seating the FPC, and re-closing the connector fixed it.

Allan

1 Like
3

Hi Allan, that was it!
I’d never have had the idea of a bad connection.
Thanks a lot, the Pure Thermal was languishing in a drawer and that was hard to swallow at the price of the board…
Ludo