Import project files

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>

.gitignore

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+.vscode
+build

.gitmodules

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+[submodule "pico-sdk"]
+	path = pico-sdk
+	url = git@github.com:raspberrypi/pico-sdk.git

CMakeLists.txt

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+# SPDX-License-Identifier: MIT
+
+cmake_minimum_required(VERSION 3.13)
+
+include(pico-sdk/pico_sdk_init.cmake)
+
+project(pico_uart_bridge)
+
+pico_sdk_init()
+
+add_executable(uart_bridge uart-bridge.c usb-descriptors.c)
+
+target_include_directories(uart_bridge PUBLIC
+	pico-sdk/lib/tinyusb/src
+	pico-sdk/src/rp2_common/pico_stdio_usb/include)
+
+target_link_libraries(uart_bridge
+	pico_multicore
+	pico_stdlib
+	tinyusb_device)
+
+pico_add_extra_outputs(uart_bridge)

LICENSE.md

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+The MIT License (MIT)
+=====================
+
+Copyright © 2021 Álvaro Fernández Rojas <noltari@gmail.com>
+
+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.

README.md

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+Raspberry Pi Pico USB-UART Bridge
+=================================
+
+This program bridges the Raspberry Pi Pico HW UART0 to USB CDC serial device in order to behave like any other USB-to-UART Bridge controller.
+
+Disclaimer
+----------
+
+This software is provided without warranty, according to the MIT License, and should therefore not be used where it may endanger life, financial stakes, or cause discomfort and inconvenience to others.

build.sh

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+#!/bin/sh
+
+BUILD_DIR=build
+
+main () {
+	local cur_dir=$PWD
+
+	mkdir -p $BUILD_DIR
+	cd $BUILD_DIR
+	cmake ..
+	make
+	cd $cur_dir
+}
+
+main $@

uart-bridge.c

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+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2021 Álvaro Fernández Rojas <noltari@gmail.com>
+ */
+
+#include <hardware/irq.h>
+#include <hardware/structs/sio.h>
+#include <hardware/uart.h>
+#include <pico/multicore.h>
+#include <pico/stdio_usb.h>
+#include <pico/stdlib.h>
+#include <tusb.h>
+#include <string.h>
+
+#if !defined(MIN)
+#define MIN(a, b) ((a > b) ? b : a)
+#endif /* MIN */
+
+#define LED_PIN 25
+
+#define UART_ID uart0
+#define UART_TX_PIN 0
+#define UART_RX_PIN 1
+
+#define BUFFER_SIZE	64
+
+#define DEF_BIT_RATE 115200
+#define DEF_STOP_BITS 1
+#define DEF_PARITY 0
+#define DEF_DATA_BITS 8
+
+static cdc_line_coding_t CDC_LC = {
+	.bit_rate = DEF_STOP_BITS,
+	.stop_bits = DEF_STOP_BITS,
+	.parity = DEF_PARITY,
+	.data_bits = DEF_DATA_BITS,
+};
+
+static uint8_t UART_BUFFER[BUFFER_SIZE];
+static uint32_t UART_POS = 0;
+static mutex_t UART_MTX;
+
+static uint8_t USB_BUFFER[BUFFER_SIZE];
+static uint32_t USB_POS = 0;
+static mutex_t USB_MTX;
+
+static inline uart_parity_t databits_usb2uart(uint8_t data_bits)
+{
+	switch (data_bits) {
+		case 5:
+			return 5;
+		case 6:
+			return 6;
+		case 7:
+			return 7;
+		default:
+			return 8;
+	}
+}
+
+static inline uart_parity_t parity_usb2uart(uint8_t usb_parity)
+{
+	switch (usb_parity) {
+		case 1:
+			return UART_PARITY_ODD;
+		case 2:
+			return UART_PARITY_EVEN;
+		default:
+			return UART_PARITY_NONE;
+	}
+}
+
+static inline uart_parity_t stopbits_usb2uart(uint8_t stop_bits)
+{
+	switch (stop_bits) {
+		case 2:
+			return 2;
+		default:
+			return 1;
+	}
+}
+
+int update_uart_cfg(void)
+{
+	static cdc_line_coding_t last_cdc_lc = {
+		.bit_rate = DEF_STOP_BITS,
+		.stop_bits = DEF_STOP_BITS,
+		.parity = DEF_PARITY,
+		.data_bits = DEF_DATA_BITS,
+	};
+	int updated = 0;
+
+	if (last_cdc_lc.bit_rate != CDC_LC.bit_rate) {
+		uart_set_baudrate(UART_ID, CDC_LC.bit_rate);
+		updated = 1;
+	}
+
+	if ((last_cdc_lc.stop_bits != CDC_LC.stop_bits) ||
+		(last_cdc_lc.parity != CDC_LC.parity) ||
+		(last_cdc_lc.data_bits != CDC_LC.data_bits)) {
+		uart_set_format(UART_ID, databits_usb2uart(CDC_LC.data_bits),
+						stopbits_usb2uart(CDC_LC.stop_bits),
+						parity_usb2uart(CDC_LC.parity));
+		updated = 1;
+	}
+
+	if (updated)
+		memcpy(&last_cdc_lc, &CDC_LC, sizeof(cdc_line_coding_t));
+
+	return updated;
+}
+
+void core1_entry(void)
+{
+	tusb_init();
+
+	while (1) {
+		tud_task();
+
+		if (tud_cdc_connected()) {
+			uint32_t count;
+
+			tud_cdc_get_line_coding(&CDC_LC);
+
+			/* Read bytes from USB */
+			if (tud_cdc_available()) {
+				uint32_t len;
+
+				mutex_enter_blocking(&USB_MTX);
+
+				len = MIN(tud_cdc_available(), BUFFER_SIZE - USB_POS);
+				if (len) {
+					count = tud_cdc_read(USB_BUFFER, len);
+					USB_POS += count;
+				}
+
+				mutex_exit(&USB_MTX);
+			}
+
+			/* Write bytes to USB */
+			if (UART_POS) {
+				mutex_enter_blocking(&UART_MTX);
+
+				count = tud_cdc_write(UART_BUFFER, UART_POS);
+				if (count) {
+					UART_POS -= count;
+					tud_cdc_write_flush();
+				}
+
+				mutex_exit(&UART_MTX);
+			}
+
+			gpio_put(LED_PIN, 1);
+		} else {
+			gpio_put(LED_PIN, 0);
+		}
+	};
+}
+
+int main(void)
+{
+	uint8_t ch;
+	int rc;
+
+	mutex_init(&UART_MTX);
+	mutex_init(&USB_MTX);
+
+	gpio_init(LED_PIN);
+	gpio_set_dir(LED_PIN, GPIO_OUT);
+
+	uart_init(UART_ID, CDC_LC.bit_rate);
+
+	gpio_set_function(UART_TX_PIN, GPIO_FUNC_UART);
+	gpio_set_function(UART_RX_PIN, GPIO_FUNC_UART);
+
+	uart_set_hw_flow(UART_ID, false, false);
+	uart_set_format(UART_ID, databits_usb2uart(CDC_LC.data_bits),
+		stopbits_usb2uart(CDC_LC.stop_bits),
+		parity_usb2uart(CDC_LC.parity));
+
+	multicore_launch_core1(core1_entry);
+
+	while (1) {
+		update_uart_cfg();
+
+		/* Read bytes from UART */
+		if (uart_is_readable(UART_ID)) {
+			mutex_enter_blocking(&UART_MTX);
+
+			while (uart_is_readable(UART_ID) && UART_POS < BUFFER_SIZE) {
+				UART_BUFFER[UART_POS] = uart_getc(UART_ID);
+				UART_POS++;
+			}
+
+			mutex_exit(&UART_MTX);
+		}
+
+		/* Write bytes to UART */
+		if (USB_POS) {
+			mutex_enter_blocking(&USB_MTX);
+
+			uart_write_blocking(UART_ID, USB_BUFFER, USB_POS);
+			USB_POS = 0;
+
+			mutex_exit(&USB_MTX);
+		}
+	}
+
+	return 0;
+}