CircuitPython i2ctarget with large transaction payloads

code.py

# atmel-samd i2ctarget (only reads):

import time
import binascii
import board
import busio
from i2ctarget import I2CTarget

I2C_ADDRESS = 0x40

# Feather M4 Express
with I2CTarget(scl=board.SCL, sda=board.SDA, addresses=(I2C_ADDRESS, 0x41)) as device:
    print(f"{time.monotonic_ns()} START 0x{I2C_ADDRESS:02X}")
    while True:
        req = device.request(timeout=-1)  # Zero means wait forever, a negative value means check once
        if not req:
            print(f"{time.monotonic_ns()}", end="\r")
            continue
        with req:
            print()
            if not req.is_read:  # incoming request is a write  # req.is_restart == False
                inbuf = req.read(n=-1)  # n – Number of bytes to read (negative means all)
 
                body = inbuf[0:len(inbuf)-8]
                crc_calc = f"{binascii.crc32(body):08x}".encode()
                crc_read = inbuf[len(inbuf)-8:len(inbuf)]
                if crc_calc == crc_read:
                    print(f"{time.monotonic_ns()} 🟢 READ {len(inbuf)} {crc_calc} {crc_read} {inbuf}")
                else:
                    print(f"{time.monotonic_ns()} 🟠 READ {req.address} {len(inbuf)} {crc_calc} {crc_read} {inbuf}")

Multi-controller, multi-target:
https://fosstodon.org/@anecdata/114688874119367988