examples/usb: Add a very simple USBDevice example with host.

Signed-off-by: Damien George <damien@micropython.org>

examples/usb/usb_simple_device.py

@@ -0,0 +1,144 @@
+# Implementation of a very simple, custom USB device in Python.  The device has an
+# IN and OUT endpoint, accepts up to 64 bytes of data on the OUT endpoint, and echos
+# that data back to the IN endpoint.
+#
+# To run, just execute this file on a device with machine.USBDevice support.  The device
+# will then change to the custom USB device.
+#
+# For example, use `mpremote` (the `--no-follow` option starts the script running
+# without waiting for a response, because there won't be a response after the device
+# changes its USB mode):
+#
+# $ mpremote run --no-follow usb_simple_device.py
+#
+# Then, run the host side of the example on your PC using:
+#
+# $ sudo python usb_simple_host_pyusb.py
+#
+# You'll need to have `pyusb` installed via `pip install pyusb` to run the host PC code.
+# And `sudo` is most likely needed to access the custom USB device.
+#
+# Once you have finished running the code, you will need to reset or unplug the USB
+# device to stop it.
+
+import machine
+
+# VID and PID of the USB device.
+VID = 0xF055
+PID = 0x9999
+
+# USB endpoints used by the device.
+EP_OUT = 0x01
+EP_IN = 0x81
+
+# USB device descriptor.
+_desc_dev = bytes(
+    [
+        0x12,  # bLength
+        0x01,  # bDescriptorType: Device
+        0x00,
+        0x02,  # USB version: 2.00
+        0xFF,  # bDeviceClass: vendor
+        0x00,  # bDeviceSubClass
+        0x01,  # bDeviceProtocol
+        0x40,  # bMaxPacketSize
+        VID & 0xFF,
+        VID >> 8 & 0xFF,  # VID
+        PID & 0xFF,
+        PID >> 8 & 0xFF,  # PID
+        0x00,
+        0x01,  # bcdDevice: 1.00
+        0x11,  # iManufacturer
+        0x12,  # iProduct
+        0x13,  # iSerialNumber
+        0x01,  # bNumConfigurations: 1
+    ]
+)
+
+# USB configuration descriptor.
+_desc_cfg = bytes(
+    [
+        # Configuration Descriptor.
+        0x09,  # bLength
+        0x02,  # bDescriptorType: configuration
+        0x20,
+        0x00,  # wTotalLength: 32
+        0x01,  # bNumInterfaces
+        0x01,  # bConfigurationValue
+        0x14,  # iConfiguration
+        0xA0,  # bmAttributes
+        0x96,  # bMaxPower
+        # Interface Descriptor.
+        0x09,  # bLength
+        0x04,  # bDescriptorType: interface
+        0x00,  # bInterfaceNumber
+        0x00,  # bAlternateSetting
+        0x02,  # bNumEndpoints
+        0xFF,  # bInterfaceClass
+        0x03,  # bInterfaceSubClass
+        0x00,  # bInterfaceProtocol
+        0x15,  # iInterface
+        # Endpoint IN1.
+        0x07,  # bLength
+        0x05,  # bDescriptorType: endpoint
+        EP_IN,  # bEndpointAddress
+        0x03,  # bmAttributes: interrupt
+        0x40,
+        0x00,  # wMaxPacketSize
+        0x0A,  # bInterval
+        # Endpoint OUT1.
+        0x07,  # bLength
+        0x05,  # bDescriptorType: endpoint
+        EP_OUT,  # bEndpointAddress
+        0x02,  # bmAttributes: bulk
+        0x40,
+        0x00,  # wMaxPacketSize
+        0x00,  # bInterval
+    ]
+)
+
+# USB strings.
+_desc_strs = {
+    0x11: b"iManufacturer",
+    0x12: b"iProduct",
+    0x13: b"iSerial",
+    0x14: b"iInterface",
+    0x15: b"iInterface",
+    0x16: b"Extra information",
+}
+
+
+# USB callback for when our custom USB interface is opened by the host.
+def _open_itf_cb(interface_desc_view):
+    print("_open_itf_cb", bytes(interface_desc_view))
+    # Prepare to receive first data packet on the OUT endpoint.
+    usbd.submit_xfer(EP_OUT, usbd_buf)
+
+
+# USB callback for when a data transfer (IN or OUT) has completed.
+def _xfer_cb(ep_addr, result, xferred_bytes):
+    print("_xfer_cb", ep_addr, result, xferred_bytes)
+    if ep_addr == EP_OUT:
+        # Received data packet from the host, print it out.
+        print(usbd_buf)
+        # And then echo the data back to the host.
+        usbd.submit_xfer(EP_IN, memoryview(usbd_buf)[:xferred_bytes])
+    elif ep_addr == EP_IN:
+        # Host got our data, prepare to receive the next data packet.
+        usbd.submit_xfer(EP_OUT, usbd_buf)
+
+
+# USB data buffer, for IN and OUT transfers.
+usbd_buf = bytearray(64)
+
+# Switch the USB device to our custom USB driver.
+usbd = machine.USBDevice()
+usbd.builtin_driver = usbd.BUILTIN_NONE
+usbd.config(
+    desc_dev=_desc_dev,
+    desc_cfg=_desc_cfg,
+    desc_strs=_desc_strs,
+    open_itf_cb=_open_itf_cb,
+    xfer_cb=_xfer_cb,
+)
+usbd.active(1)

examples/usb/usb_simple_host_pyusb.py

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+#!/usr/bin/env python3
+#
+# Host side of the `usb_simple_device.py` example.  This must be run using standard
+# Python on a PC.  See further instructions in `usb_simple_device.py`.
+
+import sys
+import usb.core
+import usb.util
+
+# VID and PID of the custom USB device.
+VID = 0xF055
+PID = 0x9999
+
+# USB endpoints used by the device.
+EP_OUT = 0x01
+EP_IN = 0x81
+
+
+def main():
+    # Search for the custom USB device by VID/PID.
+    dev = usb.core.find(idVendor=VID, idProduct=PID)
+
+    if dev is None:
+        print("No USB device found")
+        sys.exit(1)
+
+    # Claim the USB device.
+    usb.util.claim_interface(dev, 0)
+
+    # Read the device's strings.
+    for i in range(0x11, 0x17):
+        print(f"str{i}:", usb.util.get_string(dev, i))
+
+    # Test writing to the device.
+    ret = dev.write(EP_OUT, b"01234567", timeout=1000)
+    print(ret)
+
+    # Test reading from the device.
+    print(dev.read(EP_IN, 64))
+
+    # Release the USB device.
+    usb.util.release_interface(dev, 0)
+    usb.util.dispose_resources(dev)
+
+
+if __name__ == "__main__":
+    main()