USB VCP example.

# This work is licensed under the MIT license.
# Copyright (c) 2013-2023 OpenMV LLC. All rights reserved.
# https://github.com/openmv/openmv/blob/master/LICENSE
#
# USB VCP example.
# This example shows how to use the USB VCP class to send an image to PC on demand.
#
# WARNING:
# This script should NOT be run from the IDE or command line, it should be saved as main.py
# Note the following commented script shows how to receive the image from the host side.
#
# #!/usr/bin/env python2.7
# import sys, serial, struct
# port = '/dev/ttyACM0'
# sp = serial.Serial(port, baudrate=115200, bytesize=serial.EIGHTBITS, parity=serial.PARITY_NONE,
#             xonxoff=False, rtscts=False, stopbits=serial.STOPBITS_ONE, timeout=None, dsrdtr=True)
# sp.setDTR(True) # dsrdtr is ignored on Windows.
# sp.write("snap")
# sp.flush()
# size = struct.unpack('<L', sp.read(4))[0]
# img = sp.read(size)
# sp.close()
#
# with open("img.jpg", "w") as f:
#     f.write(img)

import csi
import struct
from pyb import USB_VCP

usb = USB_VCP()

csi0 = csi.CSI()
csi0.reset()  # Reset and initialize the sensor.
csi0.pixformat(csi.RGB565)  # Set pixel format to RGB565 (or GRAYSCALE)
csi0.framesize(csi.QVGA)  # Set frame size to QVGA (320x240)
csi0.snapshot(time=2000)  # Wait for settings take effect.

while True:
    cmd = usb.recv(4, timeout=5000)
    if cmd == b"snap":
        img = csi0.snapshot().to_jpeg()
        usb.send(struct.pack("<L", img.size()))
        usb.send(img)