Demonstrate external SD card in CircuitPython (on LILYGO ESP32-S2 board https://circuitpython.org/board/lilygo_ttgo_t8_s2_st7789/ )

lilygo_esp32s2_imagedisplay.py

# lilygo_esp32s2_imagedisplay.py
# 25 Jul 2021 - todbot / Tod Kurt
# SD card handling from:
# https://learn.adafruit.com/adafruit-micro-sd-breakout-board-card-tutorial/circuitpython
import busio
import sdcardio
import storage
import os

sd_spi = busio.SPI(clock=board.SD_CLK, MOSI=board.SD_MOSI, MISO=board.SD_MISO)

img_files=[]
img_tilegrids=displayio.Group()
img_bitmaps=[]
try:
    sdcard = sdcardio.SDCard(sd_spi, cs=board.SD_CS)
    vfs = storage.VfsFat(sdcard)
    storage.mount(vfs, "/sd")
    for fn in os.listdir('/sd'):
        print(fn)
        if fn.lower().endswith('.bmp') and not fn.startswith('.'):
            ffn = "/sd/"+fn
            print("using ",ffn)
            img_files.append(ffn)
            bitmap, palette = adafruit_imageload.load(ffn,
                                                      bitmap=displayio.Bitmap,
                                                      palette=displayio.Palette)
            tilegrid = displayio.TileGrid(bitmap, pixel_shader=palette)
            img_tilegrids.append(tilegrid)
except OSError as e:
    print("error:",e)
    
print("Hello World!", sd_spi.frequency)
print("imgs:",img_files)
print("img tiles:",img_tilegrids)

display.auto_refresh = False
screen.append(img_tilegrids)
while True:
    for t in img_tilegrids:
        #print("boop", gc.mem_free(), t.x, t.y, t.pixel_shader)
        t.hidden = False
        display.refresh()
        t.hidden = True
        #time.sleep(0.1)
        
while True:
    for t in img_tilegrids:
        print("boop", gc.mem_free(), t.x, t.y, t.pixel_shader)
        screen.append(t)
        display.refresh()
        #time.sleep(0.01)
        screen.pop()

while True:
    for fn in img_files:
        print("displaying", fn, "at:", sd_spi.frequency)
        with open(fn,'rb') as f:
            odb = displayio.OnDiskBitmap(f)
            bitmap = displayio.TileGrid(odb, pixel_shader=odb.pixel_shader)
            screen.append(bitmap)
            # Wait for the image to load.
            display.refresh() #  target_frames_per_second=5)
            time.sleep(5)
            screen.pop() # remove bitmap so we don't run out of memory