framebuf ValueError: problem

[ctimmer]

I don't know why I'm get a ValueError with the code below. The bytearray should be large enough. It works if I set byte buf_len to at least 350.

Environment:
MicroPython v1.29.0 on 2026-08-24; Raspberry Pi Pico W with RP2040

Output:

byte_buf_len: 313
Traceback (most recent call last):
  File "<stdin>", line 19, in <module>
ValueError: 

Code:

import framebuf
import math

WIDTH = 50
HEIGHT = 50
#WIDTH = 400  # This works
#HEIGHT = 300
PIXEL_BITS = 1     # bits per pixel

byte_buf_len = math.ceil ((WIDTH * HEIGHT * PIXEL_BITS) / 8)
print ("byte_buf_len:", byte_buf_len)

byte_buf = bytearray (byte_buf_len)

frame_buf = framebuf.FrameBuffer (byte_buf ,
                                    WIDTH ,
                                    HEIGHT ,
                                    framebuf.MONO_HMSB)

[GitHubsSilverBullet]

byte_buf_len = ceil(WIDTH * PIXEL_BITS / 8) * HEIGHT
WIDTH * PIXEL_BITS must be divisible by 8.

[ctimmer]

Thanks for the quick response
Curt