stdio (optionally) directly over USB-CDC instead of UART loopback

CMakeLists.txt

@@ -1,6 +1,7 @@
 option(USE_SYSTEMWIDE_PICOSDK "Use the systemwide Pico SDK instead of relying on the one from a deeply nested Git submodule (OFF by default)" OFF)
 option(PICO_NO_FLASH "Disable writing the compiled program to flash, and only load it to RAM. Useful for testing, but not much else (OFF by default)." OFF)
 option(PICO_COPY_TO_RAM "Run all code in RAM, while the program is also stored on flash. On bootup, everything will be copied to RAM (OFF by default)." OFF)
+option(USE_USBCDC_FOR_STDIO "Export an extra USB-CDC interface for stdio, instead of echoing it to a UART port (and requiring UART loopback for receiving stdio output on a host computer)." OFF)
 set(FAMILY "rp2040" CACHE STRING "Board/MCU family, decides which drivers to use. Set to RP2040 by default.")
 set(BOARD "raspberry_pi_pico" CACHE STRING "Board used, determines the pinout. Defaults to the Raspberry Pi Pico.")
 
@@ -27,10 +28,14 @@ if(FAMILY STREQUAL "rp2040")
   pico_sdk_init()
   add_executable(${PROJECT})
 
-  include(${TOP}/hw/bsp/${FAMILY}/family.cmake)
-
   # need uart stdio, usb is busy doing other stuff
-  pico_enable_stdio_uart(${PROJECT} 1)
+  if(USE_USBCDC_FOR_STDIO)
+    # we're going to manually implement this case
+    pico_enable_stdio_uart(${PROJECT} 0)
+    target_compile_definitions(${PROJECT} PUBLIC USE_USBCDC_FOR_STDIO=1 PICO_STDIO_USB=1)
+  else()
+    pico_enable_stdio_uart(${PROJECT} 1)
+  endif()
   pico_enable_stdio_usb(${PROJECT} 0)
 
   # Example source
@@ -48,8 +53,7 @@ if(FAMILY STREQUAL "rp2040")
     ${CMAKE_CURRENT_SOURCE_DIR}/cdc_serprog.c
     ${CMAKE_CURRENT_SOURCE_DIR}/rtconf.c
   )
-
+  # Example include
- # Example include
   target_include_directories(${PROJECT} PUBLIC
     ${CMAKE_CURRENT_SOURCE_DIR}/
     ${CMAKE_CURRENT_SOURCE_DIR}/libco/
@@ -59,13 +63,34 @@ if(FAMILY STREQUAL "rp2040")
     ${CMAKE_CURRENT_SOURCE_DIR}/bsp/default/
   )
 
+  # need to do this AFTER the regular includes, so that our bsp folder can
+  # override the tinyusb board.h header
+  include(${TOP}/hw/bsp/${FAMILY}/family.cmake) # tinyusb hardware-specific stuff
+
   # Example defines
-  target_compile_definitions(${PROJECT} PUBLIC
+  #target_compile_definitions(${PROJECT} PUBLIC
-  )
+  #)
 
   target_link_libraries(${PROJECT} pico_stdlib pico_unique_id hardware_spi
     pico_fix_rp2040_usb_device_enumeration)
 
+  if(USE_USBCDC_FOR_STDIO)
+    target_sources(${PROJECT} PUBLIC
+      ${CMAKE_CURRENT_SOURCE_DIR}/bsp/${FAMILY}/cdc_stdio.c
+    )
+
+    target_include_directories(${PROJECT} PUBLIC
+      ${PICO_SDK_PATH}/src/rp2_common/pico_stdio_usb/include/
+    )
+
+    # extremely ugly hack to prevent the Pico SDK to declare *its* TinyUSB config
+    target_compile_definitions(${PROJECT} PUBLIC
+      _PICO_STDIO_USB_TUSB_CONFIG_H=1
+    )
+
+    target_link_libraries(${PROJECT} pico_stdio)
+  endif()
+
   pico_add_extra_outputs(${PROJECT})
 
 else()

README.md

@@ -127,7 +127,7 @@ libco is licensed under the [ISC license](https://opensource.org/licenses/ISC)
         separate mode that temporarily disables all other IO protocols
 - [x] UART with CTS/RTS flow control
   - [x] Needs configurable stuff as well, as some UART interfaces won't use this.
-- [ ] Debug interface to send printf stuff directly to USB, instead of having
+- [x] Debug interface to send printf stuff directly to USB, instead of having
 -     to use the UART interface as a loopback thing.
 - [ ] I2C support by emulating the I2C Tiny USB
   - [ ] Expose RP2040-internal temperature ADC on I2C-over-USB bus?

bsp/rp2040/board.h

@@ -0,0 +1,51 @@
+/* 
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2021, Ha Thach (tinyusb.org)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ *
+ * This file is part of the TinyUSB stack.
+ */
+
+#ifndef BOARD_H_
+#define BOARD_H_
+
+#ifdef __cplusplus
+ extern "C" {
+#endif
+
+#define LED_PIN               PICO_DEFAULT_LED_PIN
+#define LED_STATE_ON          1
+
+// Button pin is BOOTSEL which is flash CS pin
+#define BUTTON_BOOTSEL
+#define BUTTON_STATE_ACTIVE   0
+
+#ifndef USE_USBCDC_FOR_STDIO
+#define UART_DEV              uart0
+#define UART_TX_PIN           0
+#define UART_RX_PIN           1
+#endif
+
+#ifdef __cplusplus
+ }
+#endif
+
+#endif /* BOARD_H_ */

bsp/rp2040/cdc_stdio.c

@@ -0,0 +1,105 @@
+
+#include <pico/time.h>
+#include <pico/stdio.h>
+#include <pico/stdio/driver.h>
+#include <pico/binary_info.h>
+#include <pico/mutex.h>
+#include <hardware/irq.h>
+
+#include "tusb.h"
+
+#include "protocfg.h"
+
+#ifndef PICO_STDIO_USB_STDOUT_TIMEOUT_US
+#define PICO_STDIO_USB_STDOUT_TIMEOUT_US 500000
+#endif
+
+// *mostly* the same as the SDK code, *except* we have to explicitely pass the
+// CDC interface number to the tusb functions, making the SDK code itself very
+// non-reusable >__>
+
+static mutex_t stdio_usb_mutex;
+
+static void stdio_usb_out_chars(const char* buf, int length) {
+	static uint64_t last_avail_time;
+	uint32_t owner;
+
+	if (!mutex_try_enter(&stdio_usb_mutex, &owner)) {
+		if (owner == get_core_num()) return; // would deadlock otherwise
+		mutex_enter_blocking(&stdio_usb_mutex);
+	}
+
+	if (tud_cdc_n_connected(CDC_N_STDIO)) {
+		for (int i = 0; i < length; ) {
+			int n = length - i;
+			int avail = tud_cdc_n_write_available(CDC_N_STDIO);
+
+			if (n > avail) n = avail;
+			if (n) {
+				int n2 = tud_cdc_n_write(CDC_N_STDIO, buf+i, n);
+				tud_task();
+				tud_cdc_n_write_flush(CDC_N_STDIO);
+				i += n2;
+				last_avail_time = time_us_64();
+			} else {
+				tud_task();
+				tud_cdc_n_write_flush(CDC_N_STDIO);
+
+				if (!tud_cdc_n_connected(CDC_N_STDIO) ||
+						(!tud_cdc_n_write_available(CDC_N_STDIO)
+						 && time_us_64() > last_avail_time + PICO_STDIO_USB_STDOUT_TIMEOUT_US)) {
+					break;
+				}
+			}
+		}
+	} else {
+		// reset our timeout
+		last_avail_time = 0;
+	}
+
+	mutex_exit(&stdio_usb_mutex);
+}
+
+static int stdio_usb_in_chars(char* buf, int length) {
+	uint32_t owner;
+
+	if (!mutex_try_enter(&stdio_usb_mutex, &owner)) {
+		if (owner == get_core_num()) return PICO_ERROR_NO_DATA; // would deadlock otherwise
+		mutex_enter_blocking(&stdio_usb_mutex);
+	}
+
+	int rc = PICO_ERROR_NO_DATA;
+
+	if (tud_cdc_n_connected(CDC_N_STDIO) && tud_cdc_n_available(CDC_N_STDIO)) {
+		int count = tud_cdc_n_read(CDC_N_STDIO, buf, length);
+		rc = count ? count : PICO_ERROR_NO_DATA;
+	}
+
+	mutex_exit(&stdio_usb_mutex);
+
+	return rc;
+}
+
+extern stdio_driver_t stdio_usb;
+stdio_driver_t stdio_usb = {
+	.out_chars = stdio_usb_out_chars,
+	. in_chars = stdio_usb_in_chars ,
+#if PICO_STDIO_ENABLE_CRLF_SUPPORT
+	.crlf_enabled = PICO_STDIO_DEFAULT_CRLF
+#endif
+};
+
+bool stdio_usb_init(void) {
+//#if !PICO_NO_BI_STDIO_USB
+	bi_decl_if_func_used(bi_program_feature("USB stdin / stdout"));
+//#endif
+
+	mutex_init(&stdio_usb_mutex);
+
+	// unlike with the SDK code, we don't need to add IRQ stuff for the USB
+	// task, as our main function handles this automatically
+
+	stdio_set_driver_enabled(&stdio_usb, true);
+	return true;
+}
+

bsp/rp2040/protocfg.h

@@ -11,5 +11,9 @@
 #define CDC_N_UART 0
 #define CDC_N_SERPROG 1
 
+#ifdef USE_USBCDC_FOR_STDIO
+#define CDC_N_STDIO 2
+#endif
+
 #endif
 

main.c

@@ -27,6 +27,8 @@
 #include <stdio.h>
 #include <string.h>
 
+#include "tusb_config.h"
+
 #include "bsp/board.h" /* a tinyusb header */
 #include "tusb.h"
 
@@ -95,7 +97,7 @@ int main(void)
   mainthread = co_active();
 
   // TODO: split this out in a bsp-specific file
-#ifdef PICO_BOARD
+#if defined(PICO_BOARD) && !defined(USE_USBCDC_FOR_STDIO)
   // use hardcoded values from TinyUSB board.h
   bi_decl(bi_2pins_with_func(0, 1, GPIO_FUNC_UART));
 #endif
@@ -117,6 +119,10 @@ int main(void)
 
   tusb_init();
 
+#ifdef USE_USBCDC_FOR_STDIO
+  stdio_usb_init();
+#endif
+
   while (1)
   {
     //printf("hi\n");

protos.h

@@ -2,11 +2,11 @@
 #ifndef PROTOS_H_
 #define PROTOS_H_
 
+#include <stdbool.h>
+
 #include "protocfg.h"
 
 #ifdef DBOARD_HAS_UART
-#include <stdbool.h>
-
 void cdc_uart_init(void);
 void cdc_uart_task(void);
 
@@ -18,5 +18,11 @@ void cdc_serprog_init(void);
 void cdc_serprog_task(void);
 #endif
 
+#ifdef USE_USBCDC_FOR_STDIO
+//#ifndef PICO_BOARD
+bool stdio_usb_init(void);
+//#endif
+#endif
+
 #endif
 

serprog.h

@@ -25,6 +25,8 @@ enum serprog_cmd {
 	S_CMD_SPIOP       = 0x13,
 	S_CMD_S_SPI_FREQ  = 0x14,
 	S_CMD_S_PINSTATE  = 0x15,
+
+	S_CMD_MAGIC_SETTINGS = 0x53
 };
 
 enum serprog_response {

tusb_config.h

@@ -23,8 +23,8 @@
  *
  */
 
-#ifndef _TUSB_CONFIG_H_
+#ifndef _TUSB_CONFIG_H__
-#define _TUSB_CONFIG_H_
+#define _TUSB_CONFIG_H__
 
 #ifdef __cplusplus
  extern "C" {
@@ -98,7 +98,12 @@
 #endif
 
 //------------- CLASS -------------//
+#ifdef USE_USBCDC_FOR_STDIO
+#define CFG_TUD_CDC               3
+#else
 #define CFG_TUD_CDC               2
+#endif
+
 #define CFG_TUD_MSC               0
 #define CFG_TUD_HID               1
 #define CFG_TUD_MIDI              0

usb_descriptors.c

@@ -115,6 +115,11 @@ enum
   ITF_NUM_CDC_SERPROG_DATA,
 #endif
 
+#ifdef USE_USBCDC_FOR_STDIO
+  ITF_NUM_CDC_STDIO_COM,
+  ITF_NUM_CDC_STDIO_DATA,
+#endif
+
   ITF_NUM_TOTAL
 };
 
@@ -129,6 +134,9 @@ static const int CONFIG_TOTAL_LEN = TUD_CONFIG_DESC_LEN
 #endif
 #ifdef DBOARD_HAS_SERPROG
     + TUD_CDC_DESC_LEN
+#endif
+#ifdef USE_USBCDC_FOR_STDIO
+    + TUD_CDC_DESC_LEN
 #endif
     ;
 
@@ -139,6 +147,9 @@ static const int CONFIG_TOTAL_LEN = TUD_CONFIG_DESC_LEN
 #define EPNUM_CDC_SERPROG_OUT   0x05 // 7
 #define EPNUM_CDC_SERPROG_IN    0x85 // 8
 #define EPNUM_CDC_SERPROG_NOTIF 0x86 // 6
+#define EPNUM_CDC_STDIO_OUT     0x07
+#define EPNUM_CDC_STDIO_IN      0x87
+#define EPNUM_CDC_STDIO_NOTIF   0x88
 
 // NOTE: if you modify this table, don't forget to keep tusb_config.h up to date as well!
 uint8_t const desc_configuration[] =
@@ -160,6 +171,11 @@ uint8_t const desc_configuration[] =
   // Interface number, string index, EP notification address and size, EP data address (out, in) and size.
   TUD_CDC_DESCRIPTOR(ITF_NUM_CDC_SERPROG_COM, 0, EPNUM_CDC_SERPROG_NOTIF, 64, EPNUM_CDC_SERPROG_OUT, EPNUM_CDC_SERPROG_IN, 64),
 #endif
+
+#ifdef USE_USBCDC_FOR_STDIO
+  // Interface number, string index, EP notification address and size, EP data address (out, in) and size.
+  TUD_CDC_DESCRIPTOR(ITF_NUM_CDC_STDIO_COM, 0, EPNUM_CDC_STDIO_NOTIF, 64, EPNUM_CDC_STDIO_OUT, EPNUM_CDC_STDIO_IN, 64),
+#endif
 };
 
 // Invoked when received GET CONFIGURATION DESCRIPTOR