Noob question: please help me understand why im wrong; SYNTAX errors???

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Noob question: please help me understand why im wrong; SYNTAX errors???

Post by pythagoratheorem » Mon Jan 11, 2021 8:43 pm

trying to update an old project line for line, but i have reached an impasse and i think it may be an issue later. (im aware there are other errors and issues, this is my main concern, but if you see any, please LMK)

ESP8266 Generic, ssd1306 oled screen, i2c connection

screen works, everything is properly connected.

trying to pass this line works fine:

GOTO = lambda col, row: i2c.writeto(DISPLAY,COMMAND+(0xb0+row).to_bytes(1)+COMMAND+(col&0x0f).to_bytes(1)+COMMAND+(0x10|col>>4).to_bytes(1))

but i get an error when i add GOTO (0,0) as the next line. it gives me

File "<stdin>", line xx, in <module>
File "<stdin>", line xx, in <lambda>
TypeError: function missing 1 required positional arguments


import gc
import machine
Import esp
import time
import network

# Configure GPIO pins 0 and 2 to be used for
# the I²C interface

# From the docs here:
COMMAND = b'\x80'
DATA = b'\x40'


# Each I²C device has an address, 60 (0x3c) is the address of the display
# One row (page in the docs) is 8 pixels high
FILL_ROW = lambda row,val: i2c.writeto(DISPLAY, COMMAND+(0xb0+row).to_bytes(1)+DATA+(val.to_bytes(1)) * 128)
# Move the 'graphics cursor' to position col, row. Col is offset from left in pixels, row is offset from top in pixels*8
GOTO = lambda col,row: i2c.writeto(DISPLAY, COMMAND+(0xb0+row).to_bytes(1)+COMMAND+(col&0x0f).to_bytes(1)+COMMAND+(0x10|col>>4).to_bytes(1))

# Make the display be blank
def CLEAR():
for i in range(8):
FILL_ROW(i, 0x00)

# Make sure the display is off while we set things up
# Because the display is powered from the board, you have to tell it to
# boost the voltages internally before anything happens

# Row 0 defaults to the bottom of the screen, This makes Row 0 the top
# Column 0 defaults to the right edge of the screen, This makes it the left
# Start with a blank screen (display data can be random on power-on)

# Turn the display on
i2c.writeto(DISPLAY, DISPLAY_ON)
# Move the grahics cursor top top-left
# Show some lines on the screen so we know something is going on
FILL_ROW(2, 0xaa)

# Configure the wifi networking
wlan.connect('<NETGEAR02>', '<sunnystreet319>')
ip = ''
while ip == '':
ip, _, gw, _ = wlan.ifconfig()

# Connect to the telnet server
import socket
_, _, _, _, addr = socket.getaddrinfo("", 23)[0]
sock = socket.socket()

# Set blocking = false to alllow us to just get the data that's arrived
# without worrying too much about how much is there

# The star wars ascii data is output to an 80 x 18 CHARACTER terminal window.
# Out display is 128x64 PIXELS, so we have to do some scaling.
# I decided each character should take up 2x4 pixels, meaning the size of our 'window'
# would be 160 x 72 pixels big. If we ignore the pixels that fall outside this area
# (Most of the action happens in middle of the screen anyway) then we can fill the display
# with pretty action without doing too much maths (which might be a bit slow)

# This lookup table allows us to map the ascii-art of the movie
# to a 2x4 pixel block on screen.
# Basically, if the server sends a '<' char, then:
# This maps tothe values 0x6 and 0x9
# Which are 2+4 (6) and 8+1 (9)
# So the pixels become:
# 1 □ █
# 2 █ □
# 4 █ □
# 8 □ █
ord('.'): (0x4, 0x4),
ord('-'): (0x2, 0x2),
ord('_'): (0x8, 0x8),
ord('|'): (0xf, 0x0),
ord('/'): (0xc, 0x3),
ord('\\'): (0x3, 0xc),
ord('='): (0x6, 0x6),
ord('c'): (0xf, 0x9),
ord('<'): (0x6, 0x9),
ord('>'): (0x9, 0x6),

# Micropython bytes handing is a teensy bit weird (this might just be python3)
# If you index into a bytes array, you get an integer value.
# The data being read off the socket comes in bytes (good), but to do compariasons
# we need to know the numeric ordinal of several characters. Doing this outside the loop
# is probably better than inside
SPACE = ord(' ')
CR = ord('\r')

# Keep track of our current position on screen
row = 0
col = 0

# The display writes 8 vertical pixels at a time, and for speed reasons, we
# want to write one row of 8 pixels in a go. Each line
# from the telnet connection will be 4 pixels high, so we need to buffer up 2 lines
# worth of ascii art at a time, so they can be sent to the display in one go.
# rowbits, being an array of 128 x 8bits, is perfect for this, as it also matches
# the format the display expects for updating a row.
rowbits = bytearray(128)

# In a perfect world, each 'thing' we would have to handle coming from the server
# would be exactly 1 byte long. Unfortunately newlines are sent as two bytes (CR + LF),
# and escape sequences more. It seems like they're only using 2-byte escape sequences.
# Because of this, if a CR (13), or ESC (27) char is seen, we set this skip value, to
# ignore the next N bytes. This approach is 'good enough' for a reasonable output
skip = 0

# Writes the current rowbits data to the screen, using the 'row' global to work out where on
# the screen it goes
def draw_row():
global rowbits
screenrow = int(row/2 - 2.4)
if screenrow >= 0 and screenrow <= 8:
GOTO(0, screenrow)
i2c.writeto(DISPLAY, DATA+rowbits)
rowbits = bytearray(128)

# The full movie is > 1h long, so for our purposes, the loop never ends
while True:
# Read up to 200 bytes from the network. It's easy to run out of memory by setting
# the number of bytes too high
data =
# For some reason, non-blocking reads that return no data
# return None, rather than an empty byte string
if data is None:
# Give the CPU some time to find some data
for byte in data:
if skip:
skip -= 1
# 0x1b = escape byte, we assume this means to clear the screen
if byte == 0x1b:
skip = 2
row += 1 # Increment the row, because we need to flush the current row before resetting
row = 0
gc.collect() # Not 100% sure gc is needed here, but I was having memory issues
elif byte == CR: # CR indicates newline
skip = 1
row += 1
col = 0
# After finishing every other row, flush the data to display
if row % 2 == 0:
elif byte == SPACE:
col += 1
screencol = (col-4)*2 # Map a character col to screen pixel
if screencol >= 0 and screencol < 127: # Ignore pixels that are off-screen
# Look up the right shape to draw using the character. Default to a solid block
left, right = CHARS.get(byte, (0x0f, 0x0f))
if row % 2: # Row 1 appears in the top half of the row bytes, row 2 in the bottom half
left <<= 4
right <<= 4
rowbits[screencol] |= left
rowbits[screencol+1] |= right
col += 1

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Re: Noob question: please help me understand why im wrong; SYNTAX errors???

Post by jimmo » Tue Jan 12, 2021 12:14 am

pythagoratheorem wrote:
Mon Jan 11, 2021 8:43 pm
but i get an error when i add GOTO (0,0) as the next line. it gives me
I would debug this in one of two ways:

Either, change the GOTO from being a lambda to just a regular function. There's no benefit to using a lambda here, it just makes the code harder to read and debug. The additional benefit of being a function is that you can split it into multiple lines, which will give you more hints as to where the error is.

Or, I'd try and run this code in CPython instead and see if you can get a more detailed error message.

Here's an example ""

Code: Select all

COMMAND = b'\x80'

class I2C:
    def writeto(self, addr, data):
        print(addr, data)

i2c = I2C()

GOTO = lambda col,row: i2c.writeto(DISPLAY, COMMAND+(0xb0+row).to_bytes(1)+COMMAND+(col&0x0f).to_bytes(1)+COMMAND+(0x10|col>>4).to_bytes(1))


Code: Select all

Traceback (most recent call last):
  File "/home/jimmo/", line 12, in <module>
  File "/home/jimmo/", line 10, in <lambda>
    GOTO = lambda col,row: i2c.writeto(DISPLAY, COMMAND+(0xb0+row).to_bytes(1)+COMMAND+(col&0x0f).to_bytes(1)+COMMAND+(0x10|col>>4).to_bytes(1))
TypeError: to_bytes() missing required argument 'byteorder' (pos 2)
The to_bytes function requires you to specify 'little' or 'big' endian. i.e. .to_bytes(1, 'little')

I'd recommend using struct.pack for this instead though.

Code: Select all

import struct
i2c.writeto(DISPLAY, struct.pack('bbbbbb', COMMAND, 0xb0+row, COMMAND, col&0x0f, COMMAND, 0x10|col>>4)

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