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