kopia lustrzana https://github.com/peterhinch/micropython-micro-gui
ePaper: Optimise driver, improve docs.
peterhinch
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README.md
37
README.md
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@ -149,7 +149,7 @@ development so check for updates.
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7.4 [Class TSequence](./README.md#74-class-tsequence) Plotting realtime, time sequential data.
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8. [ESP32 touch pads](./README.md#8-esp32-touch-pads) Replacing buttons with touch pads.
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9. [Realtime applications](./README.md#9-realtime-applications) Accommodating tasks requiring fast RT performance.
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10. [ePaper displays](./README.md#10-epaper-displays) Using these techniques to provide a full refresh.
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10. [ePaper displays](./README.md#10-epaper-displays) Guidance on using ePaper displays.
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[Appendix 1 Application design](./README.md#appendix-1-application-design) Tab order, button layout, encoder interface, use of graphics primitives
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[Appendix 2 Freezing bytecode](./README.md#appendix-2-freezing-bytecode) Optional way to save RAM.
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@ -506,10 +506,8 @@ Supported displays are as per
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[the nano-gui list](https://github.com/peterhinch/micropython-nano-gui/blob/master/README.md#12-description).
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In general ePaper and Sharp displays are unlikely to yield good results because
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of slow and visually intrusive refreshing. However there is an exception: the
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[Waveshare pico_epaper_42](https://www.waveshare.com/pico-epaper-4.2.htm). This
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supports partial updates which work remarkably well with minimal ghosting. Note
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that it can be used with hosts other than the Pico via the supplied cable. See
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[ePaper displays](./README.md#10-epaper-displays).
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[Waveshare pico_epaper_42](https://www.waveshare.com/pico-epaper-4.2.htm). See
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[10. ePaper displays](./README.md#10-epaper-displays).
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Display drivers are documented [here](https://github.com/peterhinch/micropython-nano-gui/blob/master/DRIVERS.md).
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@ -3044,14 +3042,29 @@ The demo `gui/demos/audio.py` provides example usage.
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# 10 ePaper displays
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In general ePaper displays do not work well with micro-gui because refresh is
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slow (seconds) and visually intrusive. Some displays support partial refresh
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which is faster (hundreds of ms) and non-intrusive. The penalty is "ghosting"
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where pixels which change from black to white do so imperfectly, leaving a grey
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trace behind. The degree of ghosting varies between display types.
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The [Waveshare pico_epaper_42](https://www.waveshare.com/pico-epaper-4.2.htm)
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is currently the only fully supported ePaper display, with a hardware_setup.py
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copied or adapted from `setup_examples/pico_epaper_42_pico.py`. After an
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initial refresh the driver is put into partial mode to provide reasonably
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quick and visually satisfactory response to button events. However ghosting may
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accumulate after long periods of running, and an application may occasionally
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need to perform a full refresh. This requires the "done" interlock described
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in section 9.
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has quite a low level of ghosting. A full refresh takes about 2.1s and partial
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about 740ms. In use there is a visible lag between operating a user control and
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a visible response, but it is usable. Currently this is the only fully
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supported ePaper display.
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It has a socket for a Pico or Pico W, but also comes with a cable suitable for
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connecting to any host. The hardware_setup.py should be copied or adapted from
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`setup_examples/pico_epaper_42_pico.py`. If using the socket, default args may
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be used (see code comment).
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After an initial refresh to clear the screen the driver is put into partial
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mode. This provides a reasonably quick and visually satisfactory response to
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user inputs such as button events. See the
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[epaper demo](https://github.com/peterhinch/micropython-micro-gui/blob/main/gui/demos/epaper.py).
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This provides for a full refresh via the `reset` button. Provision of full
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refresh is application dependent. It should be done as follows:
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```python
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async def full_refresh():
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@ -94,11 +94,14 @@ EPD_partial_lut_bb1 = b"\x00\x19\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00
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\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\
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\x00\x00\x00\x00"
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# Invert: EPD is black on white
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# 483/241 us for 2000 bytes (125/250MHz)
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# Can't extend to 32 bits becaue of long ints
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@micropython.viper
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def _linv(dest:ptr8, source:ptr8, length:int):
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def _linv(dest:ptr16, source:ptr16, length:int):
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for n in range(length):
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c = source[n]
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dest[n] = c ^ 0xFF
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c: uint = source[n]
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dest[n] = c ^ 0xFFFF
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class EPD(framebuf.FrameBuffer):
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# A monochrome approach should be used for coding this. The rgb method ensures
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@ -122,6 +125,7 @@ class EPD(framebuf.FrameBuffer):
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self.height = _EPD_HEIGHT
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self.buf = bytearray(_EPD_HEIGHT * _BWIDTH)
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self.mvb = memoryview(self.buf)
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self.ibuf = bytearray(1000) # Buffer for inverted pixels
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mode = framebuf.MONO_HLSB
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self.palette = BoolPalette(mode)
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super().__init__(self.buf, _EPD_WIDTH, _EPD_HEIGHT, mode)
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@ -252,44 +256,55 @@ class EPD(framebuf.FrameBuffer):
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return not (self._busy or (self.busy_pin() == 0)) # 0 == busy
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@micropython.native
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def _line(self, start, buf=bytearray(_BWIDTH)): # Sending 50 bytes 40us at 10MHz, 12ms for 300 lines
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_linv(buf, self.mvb[start:], _BWIDTH) # Invert image data for EPD
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def _bsend(self, start, nbytes):
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buf = self.ibuf
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_linv(buf, self.mvb[start:], nbytes >> 1) # Invert image data for EPD
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self.send_bytes(buf)
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# Timing @10MHz/250MHz: full refresh 2.1s, partial 740ms
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# Blocking with split=5 740/5=150ms
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async def _as_show(self, split):
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# Time to convert and transmit 1000 bytes ~ 1ms: most of that is tx @ 10MHz
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# Yield every 16 transfers means blocking is ~16ms
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# Total convert and transmit time for 15000 bytes is ~15ms.
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# Timing @10MHz/250MHz: full refresh 2.1s, partial 740ms: the bulk of the time
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# is spent spinning on the busy pin and is CPU frequency independent.
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async def _as_show(self):
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self.send_command(b"\x13")
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lps = _EPD_HEIGHT // split
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idx = 0
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#ttt = time.ticks_ms()
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for _ in range(split): # For each segment
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for _ in range(lps):
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self._line(idx)
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idx += _BWIDTH
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await asyncio.sleep_ms(0)
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#print("Time", time.ticks_diff(time.ticks_ms(), ttt))
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fbidx = 0 # Index into framebuf
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nbytes = len(self.ibuf) # Bytes to send
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nleft = len(self.buf) # Size of framebuf
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npass = 0
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while nleft > 0:
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self._bsend(fbidx, nbytes) # Invert, buffer and send nbytes
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fbidx += nbytes # Adjust for bytes already sent
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nleft -= nbytes
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nbytes = min(nbytes, nleft)
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if not ((npass := npass + 1) % 16):
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await asyncio.sleep_ms(0) # Control blocking time
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self._updated.set()
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self.send_command(b"\x12") # Nonblocking .display_on()
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while not self.busy_pin():
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await asyncio.sleep_ms(0) # About 1.7s for full refresh
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while not self.busy_pin(): # Wait on display hardware
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await asyncio.sleep_ms(0)
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self._busy = False
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#print("Time", time.ticks_diff(time.ticks_ms(), ttt)) # ~630ms
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async def do_refresh(self, split): # For micro-gui
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assert (not self._busy), "Refresh while busy"
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await self._as_show(split) # split=5
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await self._as_show() # split=5
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def show(self): # nanogui
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if self._busy:
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raise RuntimeError('Cannot refresh: display is busy.')
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self._busy = True # Immediate busy flag. Pin goes low much later.
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if self._asyn:
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asyncio.create_task(self._as_show(5)) # split into 5 segments
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asyncio.create_task(self._as_show())
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return
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self.send_command(b"\x13")
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for j in range(_EPD_HEIGHT):
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self._line(j)
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fbidx = 0 # Index into framebuf
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nbytes = len(self.ibuf) # Bytes to send
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nleft = len(self.buf) # Size of framebuf
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while nleft > 0:
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self._bsend(fbidx, nbytes) # Invert, buffer and send nbytes
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fbidx += nbytes # Adjust for bytes already sent
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nleft -= nbytes
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nbytes = min(nbytes, nleft)
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self._busy = False
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self.display_on()
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self.wait_until_ready()
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