3.5" FeatherWing (HX8357) [FeatherM4, 4.1.0-beta.0, Library Bundle 20190615]

code.py

"""
    This test will initialize the display using displayio
    and draw a solid red background
    """

import board
import displayio
import time

print('Begin')

spi = board.SPI()
tft_cs = board.D9
tft_dc = board.D10

displayio.release_displays()
display_bus = displayio.FourWire(spi, command=tft_dc, chip_select=tft_cs)

try:
    from adafruit_hx8357 import HX8357
    display = HX8357(display_bus, width=480, height=320)
    time.sleep(5)  # https://learn.adafruit.com/adafruit-3-5-tft-featherwing/troubleshooting
    print('Display: HX8357')
except RuntimeError as e:
    print('HX8357 Error:', e)

# SPI Frequency
while not spi.try_lock():
    pass
try:
    print("SPI:", "{:>8}".format(spi.frequency), "Hz old")
    attempt_baud = 3000000
    print("SPI:", "{:>8}".format(attempt_baud), "Hz try")
    spi.configure(baudrate=attempt_baud)
except RuntimeError as e:
    print('SPI Error:', e)
finally:
    print("SPI:", "{:>8}".format(spi.frequency), "Hz new")
    spi.unlock()
print("SPI:", "{:>8}".format(spi.frequency), "Hz unlocked")

# Make the display context
splash = displayio.Group(max_size=10)
display.show(splash)

color_bitmap = displayio.Bitmap(480, 320, 1)
color_palette = displayio.Palette(1)
color_palette[0] = 0xFF0000
bg_sprite = displayio.TileGrid(color_bitmap,
                               pixel_shader=color_palette,
                               x=0, y=0)
splash.append(bg_sprite)

time.sleep(1)

display.show(None)
print("SPI:", "{:>8}".format(spi.frequency), "Hz pre-loop")

loop = 0
while True:
    time.sleep(.1)
    print(loop, "SPI:", "{:>8}".format(spi.frequency), "Hz")
    loop += 1

It looks like baudrate shouldn't be changed once the SPI display is initialized, so "slow mode" can be avoided with a different code sequence by doing any SPI frequency changes before setting up SPI devices. It will then be static for the life of the program. It's not clear whether this is intentional. Without context manager, SPI frequency does seem to persist across reloads, hardware reset, and power loss.