128 lines
5.4 KiB
Python
128 lines
5.4 KiB
Python
# Support for ST7920 (128x64 graphics) LCD displays
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#
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# Copyright (C) 2018 Kevin O'Connor <kevin@koconnor.net>
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#
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# This file may be distributed under the terms of the GNU GPLv3 license.
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import logging
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BACKGROUND_PRIORITY_CLOCK = 0x7fffffff00000000
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# Spec says 72us, but faster is possible in practice
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ST7920_CMD_DELAY = .000020
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ST7920_SYNC_DELAY = .000045
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class ST7920:
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char_right_arrow = '\x1a'
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def __init__(self, config):
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printer = config.get_printer()
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# pin config
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ppins = printer.lookup_object('pins')
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pins = [ppins.lookup_pin('digital_out', config.get(name + '_pin'))
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for name in ['cs', 'sclk', 'sid']]
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mcu = None
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for pin_params in pins:
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if mcu is not None and pin_params['chip'] != mcu:
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raise ppins.error("st7920 all pins must be on same mcu")
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mcu = pin_params['chip']
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if pin_params['invert']:
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raise ppins.error("st7920 can not invert pin")
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self.pins = [pin_params['pin'] for pin_params in pins]
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self.mcu = mcu
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self.oid = self.mcu.create_oid()
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self.mcu.add_config_object(self)
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self.send_data_cmd = self.send_cmds_cmd = None
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self.is_extended = False
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# framebuffers
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self.text_framebuffer = (bytearray(' '*64), bytearray('~'*64), 0x80)
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self.glyph_framebuffer = (bytearray(128), bytearray('~'*128), 0x40)
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self.graphics_framebuffers = [(bytearray(32), bytearray('~'*32), i)
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for i in range(32)]
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self.framebuffers = ([self.text_framebuffer, self.glyph_framebuffer]
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+ self.graphics_framebuffers)
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def build_config(self):
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self.mcu.add_config_cmd(
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"config_st7920 oid=%u cs_pin=%s sclk_pin=%s sid_pin=%s"
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" sync_delay_ticks=%d cmd_delay_ticks=%d" % (
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self.oid, self.pins[0], self.pins[1], self.pins[2],
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self.mcu.seconds_to_clock(ST7920_SYNC_DELAY),
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self.mcu.seconds_to_clock(ST7920_CMD_DELAY)))
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cmd_queue = self.mcu.alloc_command_queue()
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self.send_cmds_cmd = self.mcu.lookup_command(
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"st7920_send_cmds oid=%c cmds=%*s", cq=cmd_queue)
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self.send_data_cmd = self.mcu.lookup_command(
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"st7920_send_data oid=%c data=%*s", cq=cmd_queue)
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def send(self, cmds, is_data=False, is_extended=False):
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cmd_type = self.send_cmds_cmd
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if is_data:
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cmd_type = self.send_data_cmd
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elif self.is_extended != is_extended:
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add_cmd = 0x22
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if is_extended:
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add_cmd = 0x26
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cmds = [add_cmd] + cmds
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self.is_extended = is_extended
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cmd_type.send([self.oid, cmds], reqclock=BACKGROUND_PRIORITY_CLOCK)
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#logging.debug("st7920 %d %s", is_data, repr(cmds))
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def flush(self):
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# Find all differences in the framebuffers and send them to the chip
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for new_data, old_data, fb_id in self.framebuffers:
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if new_data == old_data:
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continue
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# Find the position of all changed bytes in this framebuffer
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diffs = [[i, 1] for i, (nd, od) in enumerate(zip(new_data, old_data))
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if nd != od]
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# Batch together changes that are close to each other
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for i in range(len(diffs)-2, -1, -1):
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pos, count = diffs[i]
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nextpos, nextcount = diffs[i+1]
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if pos + 5 >= nextpos and nextcount < 16:
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diffs[i][1] = nextcount + (nextpos - pos)
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del diffs[i+1]
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# Transmit changes
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for pos, count in diffs:
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count += pos & 0x01
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count += count & 0x01
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pos = pos & ~0x01
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chip_pos = pos >> 1
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if fb_id < 0x40:
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# Graphics framebuffer update
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self.send([0x80 + fb_id, 0x80 + chip_pos], is_extended=True)
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else:
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self.send([fb_id + chip_pos])
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self.send(new_data[pos:pos+count], is_data=True)
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old_data[:] = new_data
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def init(self):
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cmds = [0x24, # Enter extended mode
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0x40, # Clear vertical scroll address
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0x02, # Enable CGRAM access
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0x26, # Enable graphics
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0x22, # Leave extended mode
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0x02, # Home the display
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0x06, # Set positive update direction
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0x0c] # Enable display and hide cursor
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self.send(cmds)
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self.flush()
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def load_glyph(self, glyph_id, data):
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if len(data) > 32:
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data = data[:32]
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pos = min(glyph_id * 32, 96)
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self.glyph_framebuffer[0][pos:pos+len(data)] = data
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def write_text(self, x, y, data):
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if x + len(data) > 16:
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data = data[:16 - min(x, 16)]
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pos = [0, 32, 16, 48][y] + x
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self.text_framebuffer[0][pos:pos+len(data)] = data
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def write_graphics(self, x, y, row, data):
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if x + len(data) > 16:
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data = data[:16 - min(x, 16)]
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gfx_fb = y * 16 + row
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if gfx_fb >= 32:
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gfx_fb -= 32
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x += 16
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self.graphics_framebuffers[gfx_fb][0][x:x+len(data)] = data
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def clear(self):
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self.text_framebuffer[0][:] = ' '*64
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zeros = bytearray(32)
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for new_data, old_data, fb_id in self.graphics_framebuffers:
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new_data[:] = zeros
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