LCD1602 Micropython ESP8266

import machine
import time
import os

rs = machine.Pin( 5, machine.Pin.OUT, value = 0 ) #D1(5)
en = machine.Pin( 4, machine.Pin.OUT, value = 0 ) #D2(4)
d4 = machine.Pin( 0, machine.Pin.OUT, value = 0 ) #D3(0)
d5 = machine.Pin( 2, machine.Pin.OUT, value = 0 ) #D4(2)
d6 = machine.Pin( 14, machine.Pin.OUT, value = 0 ) #D5(14)
d7 = machine.Pin( 12, machine.Pin.OUT, value = 0 ) #D6(12)

def nibbles( n, lsb = 0 ):
    d7.value( n >> 7 & 1 )
    d6.value( n >> 6 & 1 )
    d5.value( n >> 5 & 1 )
    d4.value( n >> 4 & 1 )
    time.sleep_ms( 5 )
    en.value( 1 )
    time.sleep_ms( 2 )
    en.value( 0 )
    if ( lsb == 0 ):
        nibbles( n << 4, 1 )

time.sleep( 1 )
nibbles( 0x33 )
nibbles( 0x32 )
nibbles( 0x28 )
nibbles( 0x06 )
nibbles( 0x0C )
nibbles( 0x01 )
nibbles( 0x02 )
rs.value( 1 )
nibbles( 0x4F ) #O
nibbles( 0x4B ) #K
rs.value( 0 )

ts = 0
chars = 32 * [ 0x20 ] #' '
pos = 0
def processChar( chr ):
    global ts, pos, chars
    ts = max( 1, time.ticks_ms() )
    if chr == 0x0C: #^L
        chars = 32 * [ 0x20 ]
        pos = 0
    elif chr == 0x0A: #^J=\n
        pos = 16
    elif 32 <= chr <= 126: #printables
        if pos == 31:
            chars[16:31] = chars[17:32]
            chars[31] = chr
        else:
            chars[pos] = chr
            pos = pos + 1

def render():
    ts = 0
    nibbles( 0x80 ) # line0
    rs.value( 1 )
    for b in chars[0:16]:
        nibbles( b )
    rs.value( 0 )
    nibbles( 0xC0 ) # line1
    rs.value( 1 )
    for b in chars[16:32]:
        nibbles( b )
    rs.value( 0 )

def loop():
    arr = uart.read()
    if arr:
        for i in range( len( arr ) ):
            processChar( arr[ i ] )
    if ts and time.ticks_diff( time.ticks_ms(), ts ) > 200:
        render()

test = machine.Pin( 13, machine.Pin.IN, machine.Pin.PULL_UP )
if ( test.value() == 1 ):
    os.dupterm( None, 1 )
    uart = machine.UART( 0, 115200 )
    while 1:
        loop()

# Save the code above as main.py
# Connect ESP8266 to PC using USB cable while pressing Flash button on ESP8266
# Download ESP8266 micropython firmware (for example esp8266-20170108-v1.8.7.bin)
# $ pip install esptool
# $ esptool.py --port /dev/ttyUSB0 erase_flash</code>
# $ esptool.py --port /dev/ttyUSB0 --baud 115200 write_flash --flash_size=detect 0 esp8266-20170108-v1.8.7.bin</code>
# $ sudo apt install picocom
# $ picocom /dev/ttyUSB0 -b115200
# Try some python code like "1 + 1" Enter
# Replug the USB cable
# $ pip install adafruit-ampy
# $ ampy --port /dev/ttyUSB0 put main.py main.py
# $ ampy --port /dev/ttyUSB0 ls
# Unplug the ESP8266 from PC
# Connect lcd1602 and ESP8266:
# VSS<->Gnd, Vcc<->Vin(5V), V0<->Gnd, RS<->D1(GPIO5), E<->D2(GPIO4), D0<->NC, D1<->NC, D2<->NC, D3<->NC, D4<->D3(GPIO0), D5<->D4, D6<->D5(GPIO14), D7<->D6(GPIO12), A<->3V3, K<->Gnd (Note: NC means Not Connected)
# Connect esp8266 with lcd1602 to PC
# $ picocom /dev/ttyUSB0 -b115200
# Type some text (Use Ctrl+L (formfeed) to clear screen and put cursor to first line, Ctrl+J (newline) to put cursor to second line)