Created
June 17, 2019 17:40
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3.5" FeatherWing (HX8357) [FeatherM4, 4.1.0-beta.0, Library Bundle 20190615]
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""" | |
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 |
Once restored to "normal" beta mode, spi.configure(baudrate=x)
is sticky again:
Begin
Display: HX8357
SPI: 3000000 Hz old
SPI: 3000000 Hz try
SPI: 3000000 Hz new
SPI: 3000000 Hz unlocked
SPI: 3000000 Hz pre-loop
0 849656000000 SPI: 3000000 Hz
1 851557000000 SPI: 3000000 Hz
2 853458000000 SPI: 3000000 Hz
3 855359000000 SPI: 3000000 Hz
4 857260000000 SPI: 3000000 Hz
5 859161000000 SPI: 3000000 Hz
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.
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With this code running (primary change is the SPI frequency change block), pressing the reset button (with or without display actually connected) triggers the slowdown as shown:
It seems related to the SPI frequency. Once in slow mode,
spi.configure(baudrate=x)
isn't sticky.Even after a reload... same non-stickiness of SPI frequency: