Add support for resetting RP2040 via the USB connection when using pico_stdio_usb

- setting baud rate to magic value (default=1200) will cause a reset to BOOTSEL mode
	- a VENDOR interface along side the CDC interface can be used to reset via refular flash boot, or into
	  BOOTSEL mode with control for the reset_usb_boot parameters for the latter
either method can be configured/enabled/disabled via #define

src/common/pico_binary_info/include/pico/binary_info.h

@@ -23,5 +23,7 @@
 #if !PICO_ON_DEVICE && !defined(PICO_NO_BINARY_INFO)
 #define PICO_NO_BINARY_INFO 1
 #endif
+#if !PICO_NO_BINARY_INFO
 #include "pico/binary_info/code.h"
 #endif
+#endif

src/rp2_common/pico_stdio_usb/CMakeLists.txt

@@ -4,6 +4,7 @@ if (TARGET tinyusb_device_unmarked)
     target_include_directories(pico_stdio_usb INTERFACE ${CMAKE_CURRENT_LIST_DIR}/include)
 
     target_sources(pico_stdio_usb INTERFACE
+        ${CMAKE_CURRENT_LIST_DIR}/reset_interface.c
         ${CMAKE_CURRENT_LIST_DIR}/stdio_usb.c
         ${CMAKE_CURRENT_LIST_DIR}/stdio_usb_descriptors.c
     )

src/rp2_common/pico_stdio_usb/include/pico/stdio_usb.h

@@ -19,6 +19,8 @@
  *  Note this library is a developer convenience. It is not applicable in all cases; for one it takes full control of the USB device precluding your
  *  use of the USB in device or host mode. For this reason, this library will automatically disengage if you try to using it alongside \ref tinyusb_device or
  *  \ref tinyusb_host. It also takes control of a lower level IRQ and sets up a periodic background task.
+ *
+ *  This library also includes (by default) functionality to enable the RP2040 to be reset over the USB interface.
  */
 
 // PICO_CONFIG: PICO_STDIO_USB_DEFAULT_CRLF, Default state of CR/LF translation for USB output, type=bool, default=PICO_STDIO_DEFAULT_CRLF, group=pico_stdio_usb
@@ -31,7 +33,7 @@
 #define PICO_STDIO_USB_STDOUT_TIMEOUT_US 500000
 #endif
 
-// todo perhaps unnecessarily high?
+// todo perhaps unnecessarily frequent?
 // PICO_CONFIG: PICO_STDIO_USB_TASK_INTERVAL_US, Period of microseconds between calling tud_task in the background, default=1000, advanced=true, group=pico_stdio_usb
 #ifndef PICO_STDIO_USB_TASK_INTERVAL_US
 #define PICO_STDIO_USB_TASK_INTERVAL_US 1000
@@ -42,6 +44,36 @@
 #define PICO_STDIO_USB_LOW_PRIORITY_IRQ 31
 #endif
 
+// PICO_CONFIG: PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE, Enable/disable resetting into BOOTSEL mode if the host sets the baud rate to a magic value (PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE), type=bool, default=1, group=pico_stdio_usb
+#ifndef PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE
+#define PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE 1
+#endif
+
+// PICO_CONFIG: PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE, baud rate that if selected causes a reset into BOOTSEL mode (if PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE==1), default=1200, group=pico_stdio_usb
+#ifndef PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE
+#define PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE 1200
+#endif
+
+// PICO_CONFIG: PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE, Enable/disable resetting into BOOTSEL mode via an additional VENDOR USB interface - enables picotool based reset, type=bool, default=1, group=pico_stdio_usb
+#ifndef PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE
+#define PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE 1
+#endif
+
+// PICO_CONFIG: PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_BOOTSEL, If vendor reset interface is included allow rebooting to BOOTSEL mode, type=bool, default=1, group=pico_stdio_usb
+#ifndef PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_BOOTSEL
+#define PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_BOOTSEL 1
+#endif
+
+// PICO_CONFIG: PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_FLASH_BOOT, If vendor reset interface is included allow rebooting with regular flash boot, type=bool, default=1, group=pico_stdio_usb
+#ifndef PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_FLASH_BOOT
+#define PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_FLASH_BOOT 1
+#endif
+
+// PICO_CONFIG: PICO_STDIO_USB_RESET_RESET_TO_FLASH_DELAY_MS, delays in ms before rebooting via regular flash boot, default=100, group=pico_stdio_usb
+#ifndef PICO_STDIO_USB_RESET_RESET_TO_FLASH_DELAY_MS
+#define PICO_STDIO_USB_RESET_RESET_TO_FLASH_DELAY_MS 100
+#endif
+
 #ifdef __cplusplus
 extern "C" {
 #endif

src/rp2_common/pico_stdio_usb/include/pico/stdio_usb/reset_interface.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _PICO_STDIO_USB_RESET_INTERFACE_H
+#define _PICO_STDIO_USB_RESET_INTERFACE_H
+
+// We use VENDOR, 0, 0 for PICOBOOT, so lets use VENDOR, 0, 1 for RESET
+
+// VENDOR sub-class for the reset interface
+#define RESET_INTERFACE_SUBCLASS 0x00
+// VENDOR protocol for the reset interface
+#define RESET_INTERFACE_PROTOCOL 0x01
+
+// CONTROL requests:
+
+// reset to BOOTSEL
+#define RESET_REQUEST_BOOTSEL 0x01
+// regular flash boot
+#define RESET_REQUEST_FLASH 0x02
+#endif

src/rp2_common/pico_stdio_usb/include/tusb_config.h

@@ -27,10 +27,14 @@
 #ifndef _PICO_STDIO_USB_TUSB_CONFIG_H
 #define _PICO_STDIO_USB_TUSB_CONFIG_H
 
+#include "pico/stdio_usb.h"
+
 #define CFG_TUSB_RHPORT0_MODE   (OPT_MODE_DEVICE)
 
 #define CFG_TUD_CDC             (1)
 #define CFG_TUD_CDC_RX_BUFSIZE  (256)
 #define CFG_TUD_CDC_TX_BUFSIZE  (256)
 
+// We use a vendor specific interface but with our own driver
+#define CFG_TUD_VENDOR            (0)
 #endif

src/rp2_common/pico_stdio_usb/reset_interface.c

@@ -0,0 +1,95 @@
+/**
+ * Copyright (c) 2021 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include "tusb.h"
+
+#if PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE
+#include "pico/bootrom.h"
+#include "pico/stdio_usb/reset_interface.h"
+#include "hardware/watchdog.h"
+#include "device/usbd_pvt.h"
+
+static uint8_t itf_num;
+
+static void resetd_init(void) {
+}
+
+static void resetd_reset(uint8_t __unused rhport) {
+    itf_num = 0;
+}
+
+static uint16_t resetd_open(uint8_t __unused rhport, tusb_desc_interface_t const *itf_desc, uint16_t max_len) {
+    TU_VERIFY(TUSB_CLASS_VENDOR_SPECIFIC == itf_desc->bInterfaceClass &&
+              RESET_INTERFACE_SUBCLASS == itf_desc->bInterfaceSubClass &&
+              RESET_INTERFACE_PROTOCOL == itf_desc->bInterfaceProtocol, 0);
+
+    uint16_t const drv_len = sizeof(tusb_desc_interface_t);
+    TU_VERIFY(max_len >= drv_len, 0);
+
+    itf_num = itf_desc->bInterfaceNumber;
+    return drv_len;
+}
+
+// Support for parameterized reset via vendor interface control request
+static bool resetd_control_request_cb(uint8_t __unused rhport, tusb_control_request_t const *request) {
+    if (request->wIndex == itf_num) {
+#if PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_BOOTSEL
+        if (request->bRequest == RESET_REQUEST_BOOTSEL) {
+            uint gpio_mask = 0;
+            if (request->wValue & 0x100) {
+                gpio_mask = 1u << (request->wValue >> 9u);
+            }
+            reset_usb_boot(gpio_mask, request->wValue & 0x7f);
+            // does not return, otherwise we'd return true
+        }
+#endif
+#if PICO_STDIO_USB_RESET_INTERFACE_SUPPORT_RESET_TO_FLASH_BOOT
+        if (request->bRequest == RESET_REQUEST_FLASH) {
+            watchdog_reboot(0, SRAM_END, PICO_STDIO_USB_RESET_RESET_TO_FLASH_DELAY_MS);
+            return true;
+        }
+#endif
+    }
+    return false;
+}
+
+static bool resetd_control_complete_cb(uint8_t __unused rhport, tusb_control_request_t __unused const *request) {
+    return true;
+}
+
+static bool resetd_xfer_cb(uint8_t __unused rhport, uint8_t __unused ep_addr, xfer_result_t __unused result, uint32_t __unused xferred_bytes) {
+    return true;
+}
+
+static usbd_class_driver_t const _resetd_driver =
+{
+#if CFG_TUSB_DEBUG >= 2
+    .name = "RESET",
+#endif
+    .init             = resetd_init,
+    .reset            = resetd_reset,
+    .open             = resetd_open,
+    .control_request  = resetd_control_request_cb,
+    .control_complete = resetd_control_complete_cb,
+    .xfer_cb          = resetd_xfer_cb,
+    .sof              = NULL
+};
+
+// Implement callback to add our custom driver
+usbd_class_driver_t const *usbd_app_driver_get_cb(uint8_t *driver_count) {
+    *driver_count = 1;
+    return &_resetd_driver;
+}
+#endif
+
+#if PICO_STDIO_USB_ENABLE_RESET_VIA_BAUD_RATE
+// Support for default BOOTSEL reset by changing baud rate
+void tud_cdc_line_coding_cb(uint8_t itf, cdc_line_coding_t const* p_line_coding) {
+    if (p_line_coding->bit_rate == PICO_STDIO_USB_RESET_MAGIC_BAUD_RATE) {
+        reset_usb_boot(0, 0);
+    }
+}
+#endif
+

src/rp2_common/pico_stdio_usb/stdio_usb.c

@@ -8,7 +8,6 @@
 #include "tusb.h"
 
 #include "pico/time.h"
-#include "pico/stdio_usb.h"
 #include "pico/stdio/driver.h"
 #include "pico/binary_info.h"
 #include "hardware/irq.h"

src/rp2_common/pico_stdio_usb/stdio_usb_descriptors.c

@@ -29,15 +29,26 @@
 #if !defined(TINYUSB_HOST_LINKED) && !defined(TINYUSB_DEVICE_LINKED)
 
 #include "tusb.h"
+#include "pico/stdio_usb/reset_interface.h"
 
 #define USBD_VID (0x2E8A) // Raspberry Pi
 #define USBD_PID (0x000a) // Raspberry Pi Pico SDK CDC
 
+#define TUD_RPI_RESET_DESC_LEN  9
+#if !PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE
 #define USBD_DESC_LEN (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN)
+#else
+#define USBD_DESC_LEN (TUD_CONFIG_DESC_LEN + TUD_CDC_DESC_LEN + TUD_RPI_RESET_DESC_LEN)
+#endif
 #define USBD_MAX_POWER_MA (250)
 
-#define USBD_ITF_CDC (0) // needs 2 interfaces
+#define USBD_ITF_CDC       (0) // needs 2 interfaces
-#define USBD_ITF_MAX (2)
+#if !PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE
+#define USBD_ITF_MAX       (2)
+#else
+#define USBD_ITF_RPI_RESET (2)
+#define USBD_ITF_MAX       (3)
+#endif
 
 #define USBD_CDC_EP_CMD (0x81)
 #define USBD_CDC_EP_OUT (0x02)
@@ -50,6 +61,7 @@
 #define USBD_STR_PRODUCT (0x02)
 #define USBD_STR_SERIAL (0x03)
 #define USBD_STR_CDC (0x04)
+#define USBD_STR_RPI_RESET (0x05)
 
 // Note: descriptors returned from callbacks must exist long enough for transfer to complete
 
@@ -70,12 +82,20 @@ static const tusb_desc_device_t usbd_desc_device = {
     .bNumConfigurations = 1,
 };
 
+#define TUD_RPI_RESET_DESCRIPTOR(_itfnum, _stridx) \
+  /* Interface */\
+  9, TUSB_DESC_INTERFACE, _itfnum, 0, 0, TUSB_CLASS_VENDOR_SPECIFIC, RESET_INTERFACE_SUBCLASS, RESET_INTERFACE_PROTOCOL, _stridx,
+
 static const uint8_t usbd_desc_cfg[USBD_DESC_LEN] = {
     TUD_CONFIG_DESCRIPTOR(1, USBD_ITF_MAX, USBD_STR_0, USBD_DESC_LEN,
         TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, USBD_MAX_POWER_MA),
 
     TUD_CDC_DESCRIPTOR(USBD_ITF_CDC, USBD_STR_CDC, USBD_CDC_EP_CMD,
         USBD_CDC_CMD_MAX_SIZE, USBD_CDC_EP_OUT, USBD_CDC_EP_IN, USBD_CDC_IN_OUT_MAX_SIZE),
+
+#if PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE
+    TUD_RPI_RESET_DESCRIPTOR(USBD_ITF_RPI_RESET, USBD_STR_RPI_RESET)
+#endif
 };
 
 static const char *const usbd_desc_str[] = {
@@ -83,6 +103,9 @@ static const char *const usbd_desc_str[] = {
     [USBD_STR_PRODUCT] = "Pico",
     [USBD_STR_SERIAL] = "000000000000", // TODO
     [USBD_STR_CDC] = "Board CDC",
+#if PICO_STDIO_USB_ENABLE_RESET_VIA_VENDOR_INTERFACE
+    [USBD_STR_RPI_RESET] = "Reset",
+#endif
 };
 
 const uint8_t *tud_descriptor_device_cb(void) {