tests/usbus_board_reset: test application

The test application either uses the USBUS highlevel STDIO module `stdio_acm_cdc` or it creates a CDC ACM interface to enable board reset via USBUS CDC ACM. If the `usbus_dfu` module is used together with the `riotboot_dfu` bootloader, it also initializes the USBUS DFU Runtime interface.

tests/usbus_board_reset/Makefile

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+include ../Makefile.tests_common
+
+FEATURES_REQUIRED += periph_usbdev
+
+USEMODULE += app_metadata
+USEMODULE += ps
+USEMODULE += shell
+USEMODULE += shell_cmds_default
+USEMODULE += usb_board_reset
+USEMODULE += usbus_cdc_acm
+
+DISABLE_MODULE += auto_init_usbus
+
+USB_VID ?= $(USB_VID_TESTING)
+USB_PID ?= $(USB_PID_TESTING)
+
+include $(RIOTBASE)/Makefile.include

tests/usbus_board_reset/README.md

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+# Overview
+
+This test represents a simple shell application that can be used to test
+the USB board reset function (module `usb_board_reset`) via the USB CDC ACM
+interface.
+
+It can be used to reset the board to restart either the application or the
+bootloader if supported using the `usb_board_reset` module.
+
+The test application requires that the board provides USB peripherals
+(feature `periph_usbdev`).
+
+# Usage
+
+Once the test application is flashed, the board should be detected. The output
+of command
+```
+dmesg
+```
+should look like the following and should show the USB DC ACM interface:
+```
+[1745182.057403] usb 1-4.1.2: new full-speed USB device number 69 using xhci_hcd
+[1745182.160386] usb 1-4.1.2: New USB device found, idVendor=1209, idProduct=7d01, bcdDevice= 1.00
+[1745182.160390] usb 1-4.1.2: New USB device strings: Mfr=3, Product=2, SerialNumber=4
+[1745182.160392] usb 1-4.1.2: Product: arduino-mkr1000
+[1745182.160393] usb 1-4.1.2: Manufacturer: RIOT-os.org
+[1745182.160395] usb 1-4.1.2: SerialNumber: 6B6C2CA5229020D8
+[1745182.170982] cdc_acm 1-4.1.2:1.0: ttyACM0: USB ACM device
+```
+*Note*: The interface `ttyACM0` could be different depending on which other
+        USB CDC ACM devices are already in use.
+
+For boards that use the USB CDC ACM interface as STDIO (module `stdio_cdc_acm`),
+this interface is used for the test application. Otherwise the test application
+creates a simple USB CDC ACM interface without any functionality except the
+USB board reset function.
+
+When the USB CDC ACM interface is initialized, the `stty` command can be used
+to reset the board, for example:
+```
+stty -F /dev/ttyACM0 raw ispeed 600 ospeed 600 cs8 -cstopb ignpar eol 255 eof 255
+```
+should reset the board and restart the application, while
+```
+stty -F /dev/ttyACM0 raw ispeed 1200 ospeed 1200 cs8 -cstopb ignpar eol 255 eof 255
+```
+should reset the board and start the bootloader. The latter requires that the
+bootloader supports this.

tests/usbus_board_reset/app.config.test

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+CONFIG_MODULE_APP_METADATA=y
+CONFIG_MODULE_PS=y
+CONFIG_MODULE_SHELL=y
+CONFIG_MODULE_SHELL_CMDS_DEFAULT=y
+CONFIG_MODULE_USB_BOARD_RESET=y
+CONFIG_MODULE_USBUS=y
+CONFIG_MODULE_USBUS_CDC_ACM=y
+
+CONFIG_MODULE_AUTO_INIT_USBUS=n

tests/usbus_board_reset/main.c

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+/*
+ * Copyright (C) 2022 Gunar Schorcht
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @file
+ * @brief       Simple shell application to test the USB board reset function
+ *
+ * @author      Gunar Schorcht <gunar@schorcht.net>
+ *
+ */
+
+#include <stdio.h>
+#include <string.h>
+
+#include "shell.h"
+
+#include "usb/usbus.h"
+#include "usb/usbus/cdc/acm.h"
+
+#ifdef MODULE_USBUS_DFU
+#include "usb/usbus/dfu.h"
+static usbus_dfu_device_t _dfu;
+#endif
+
+static char line_buf[SHELL_DEFAULT_BUFSIZE];
+
+static usbus_t _usbus;
+static char _stack[USBUS_STACKSIZE];
+
+static void _init(void)
+{
+    usbus_init(&_usbus, usbdev_get_ctx(0));
+
+#ifdef MODULE_STDIO_CDC_ACM
+    /* if stdio_cdc_acm is used, initialize it */
+    void usb_cdc_acm_stdio_init(usbus_t *_usbus);
+    usb_cdc_acm_stdio_init(&_usbus);
+#else
+    /* otherwise create a device CDC ACM and initialize it */
+    static usbus_cdcacm_device_t _cdcacm;
+    /* buffer is required in usbus_cdc_acm_init, use only a single character */
+    static uint8_t _cdcacm_buf;
+    usbus_cdc_acm_init(&_usbus, &_cdcacm, NULL, NULL, &_cdcacm_buf, 1);
+#endif
+
+#ifdef MODULE_USBUS_DFU
+    usbus_dfu_init(&_usbus, &_dfu, USB_DFU_PROTOCOL_RUNTIME_MODE);
+#endif
+
+    usbus_create(_stack, USBUS_STACKSIZE, USBUS_PRIO, USBUS_TNAME, &_usbus);
+}
+
+int main(void)
+{
+    _init();
+
+    shell_run(NULL, line_buf, ARRAY_SIZE(line_buf));
+
+    return 0;
+}