import serial
import time
chunk_size = 1  # размер куска
f = open(/home/user/split/music.mp3, 'rb')# Открыть file
file_content = f.read() # Содержимое .mp3 файла сохранили в file_content
f.close()
quotient = len(file_content) // chunk_size # Узнали целочисленное деление 
for k in range(0,quotient):
        with open(/home/user/split/music.mp3, 'rb') as f:
                    for chunk in iter(lambda: f.read(chunk_size), b''):
                        cmd = chunk
                        port.write(cmd)

  
>>> ifname = '/etc/passwd'
>>> 
>>> with open(ifname, 'rb') as fin:
...     block_size = 1024
...     block = fin.read(block_size)
...     while block:
...         print(len(block))
...         block = fin.read(block_size)
... 
1024
1024
796
>>>

  
>>> ifname = '/etc/passwd'
>>> 
>>> with open(ifname, 'rb') as fin:
...     block_size = 512
...     block = fin.read(block_size)
...     while block:
...         print(len(block))
...         block = fin.read(block_size)
... 
512
512
512
512
512
284
>>>