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will-v-piwill-v-pi
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Add simple UART bootloader
The sample binary flashes the LED and prints Hello, world back over the UART interface
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‎README.md‎

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App|Description
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---|---
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[enc_bootloader](bootloaders/encrypted) | A bootloader which decrypts binaries from flash into SRAM. See the separate [README](bootloaders/encrypted/README.md) for more information
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[uart_boot](bootloaders/uart) | A bootloader which boots a separate RP2350 using the UART boot interface. See section 5.8 in the datasheet for more details, including the wiring requirements
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### Clocks
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‎bootloaders/CMakeLists.txt‎

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add_subdirectory_exclude_platforms(uart host rp2040)
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if (TARGET pico_mbedtls)
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add_subdirectory_exclude_platforms(encrypted host rp2040 rp2350-riscv)
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else()

‎bootloaders/uart/CMakeLists.txt‎

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add_executable(uart_boot
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uart_boot.c
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)
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# pull in common dependencies
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target_link_libraries(uart_boot pico_stdlib hardware_flash)
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pico_embed_pt_in_binary(uart_boot ${CMAKE_CURRENT_LIST_DIR}/uart-pt.json)
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pico_set_uf2_family(uart_boot "absolute")
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# create map/bin/hex file etc.
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pico_add_extra_outputs(uart_boot)
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# add url via pico_set_program_url
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example_auto_set_url(uart_boot)
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add_executable(uart_binary
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uart_binary.c
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)
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# pull in common dependencies
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target_link_libraries(uart_binary pico_stdlib)
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pico_set_binary_type(uart_binary no_flash)
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pico_package_uf2_output(uart_binary 0x10000000)
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# create map/bin/hex/uf2 file etc.
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pico_add_extra_outputs(uart_binary)
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# call pico_set_program_url to set path to example on github, so users can find the source for an example via picotool
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example_auto_set_url(uart_binary)

‎bootloaders/uart/uart-pt.json‎

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{
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"version": [1, 0],
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"unpartitioned": {
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"families": ["absolute"],
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"permissions": {
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"secure": "rw",
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"nonsecure": "rw",
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"bootloader": "rw"
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}
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},
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"partitions": [
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{
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"start": "128K",
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"size": "32K",
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"families": ["rp2350-arm-s"],
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"permissions": {
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"secure": "rw",
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"nonsecure": "rw",
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"bootloader": "rw"
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}
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}
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]
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}

‎bootloaders/uart/uart_binary.c‎

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/**
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* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#include "pico/stdlib.h"
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#include "hardware/uart.h"
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#include "hardware/structs/pads_qspi.h"
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#include "hardware/structs/io_qspi.h"
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#ifndef LED_DELAY_MS
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#define LED_DELAY_MS 500
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#endif
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// Initialize the GPIO for the LED
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void pico_led_init(void) {
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#ifdef PICO_DEFAULT_LED_PIN
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// A device like Pico that uses a GPIO for the LED will define PICO_DEFAULT_LED_PIN
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// so we can use normal GPIO functionality to turn the led on and off
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gpio_init(PICO_DEFAULT_LED_PIN);
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gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT);
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#endif
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}
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// Turn the LED on or off
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void pico_set_led(bool led_on) {
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#if defined(PICO_DEFAULT_LED_PIN)
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// Just set the GPIO on or off
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gpio_put(PICO_DEFAULT_LED_PIN, led_on);
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#endif
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}
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// Set function for QSPI GPIO pin
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void qspi_gpio_set_function(uint gpio, gpio_function_t fn) {
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// Set input enable on, output disable off
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hw_write_masked(&pads_qspi_hw->io[gpio],
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PADS_QSPI_GPIO_QSPI_SD2_IE_BITS,
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PADS_QSPI_GPIO_QSPI_SD2_IE_BITS | PADS_QSPI_GPIO_QSPI_SD2_OD_BITS
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);
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// Zero all fields apart from fsel; we want this IO to do what the peripheral tells it.
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// This doesn't affect e.g. pullup/pulldown, as these are in pad controls.
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io_qspi_hw->io[gpio].ctrl = fn << IO_QSPI_GPIO_QSPI_SD2_CTRL_FUNCSEL_LSB;
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// Remove pad isolation now that the correct peripheral is in control of the pad
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hw_clear_bits(&pads_qspi_hw->io[gpio], PADS_QSPI_GPIO_QSPI_SD2_ISO_BITS);
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}
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int main() {
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pico_led_init();
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// SD2 is QSPI GPIO 3, SD3 is QSPI GPIO 4
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qspi_gpio_set_function(3, GPIO_FUNC_UART_AUX);
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qspi_gpio_set_function(4, GPIO_FUNC_UART_AUX);
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uart_init(uart0, 1000000);
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while (true) {
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uart_puts(uart0, "Hello, world\n");
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pico_set_led(true);
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sleep_ms(LED_DELAY_MS);
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pico_set_led(false);
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sleep_ms(LED_DELAY_MS);
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}
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}

‎bootloaders/uart/uart_boot.c‎

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#include <stdio.h>
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#include <stdlib.h>
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#include "pico/stdlib.h"
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#include "hardware/uart.h"
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#include "pico/bootrom.h"
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#include "boot/picobin.h"
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#include "hardware/flash.h"
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// UART defines for uart boot
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#define UART_ID uart1
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#define BAUD_RATE 1000000
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// Use pins 4 and 5 for uart boot
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#define UART_TX_PIN 4
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#define UART_RX_PIN 5
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// Use pin 3 for the RUN pin on the other chip
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#define RUN_PIN 3
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void reset_chip() {
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// Toggle run pin
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gpio_put(RUN_PIN, false);
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sleep_ms(1);
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gpio_put(RUN_PIN, true);
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}
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void uart_boot() {
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uint knocks = 0;
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while (true) {
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// Send the knock sequence
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uart_putc_raw(UART_ID, 0x56);
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uart_putc_raw(UART_ID, 0xff);
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uart_putc_raw(UART_ID, 0x8b);
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uart_putc_raw(UART_ID, 0xe4);
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uart_putc_raw(UART_ID, 'n');
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if (uart_is_readable_within_us(UART_ID, 1000)) {
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char in = uart_getc(UART_ID);
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printf("%c\n", in);
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break;
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} else {
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if (knocks > 10) {
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printf("No response - resetting\n");
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reset_chip();
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return;
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}
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printf("No response - knocking again\n");
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knocks++;
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}
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}
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printf("Boot starting\n");
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// Get partition location in flash
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const int buf_words = (16 * 4) + 1; // maximum of 16 partitions, each with maximum of 4 words returned, plus 1
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uint32_t* buffer = malloc(buf_words * 4);
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int ret = rom_get_partition_table_info(buffer, buf_words, PT_INFO_PARTITION_LOCATION_AND_FLAGS | PT_INFO_SINGLE_PARTITION | (0 << 24));
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assert(buffer[0] == (PT_INFO_PARTITION_LOCATION_AND_FLAGS | PT_INFO_SINGLE_PARTITION));
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assert(ret == 3);
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uint32_t location_and_permissions = buffer[1];
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uint32_t saddr = XIP_BASE + ((location_and_permissions >> PICOBIN_PARTITION_LOCATION_FIRST_SECTOR_LSB) & 0x1fffu) * FLASH_SECTOR_SIZE;
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uint32_t eaddr = XIP_BASE + (((location_and_permissions >> PICOBIN_PARTITION_LOCATION_LAST_SECTOR_LSB) & 0x1fffu) + 1) * FLASH_SECTOR_SIZE;
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printf("Start %08x, end %08x\n", saddr, eaddr);
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free(buffer);
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printf("Writing binary\n");
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uint32_t tstart = time_us_32();
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uint32_t caddr = saddr;
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while (caddr < eaddr) {
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uart_putc_raw(UART_ID, 'w');
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char *buf = (char*)caddr;
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for (int i=0; i < 32; i++) {
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uart_putc_raw(UART_ID, buf[i]);
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}
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if (!uart_is_readable_within_us(UART_ID, 500)) {
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// Detect hangs and reset the chip
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printf("Write has hung - resetting\n");
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reset_chip();
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return;
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}
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char in = uart_getc(UART_ID);
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printf("%c\n", in);
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caddr += 32;
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}
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uint32_t tend = time_us_32();
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printf("Write took %dus\n", tend - tstart);
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printf("Write complete - executing\n");
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uart_putc_raw(UART_ID, 'x');
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if (!uart_is_readable_within_us(UART_ID, 500)) {
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// Detect hangs and reset the chip
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printf("Execute has hung - resetting\n");
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reset_chip();
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return;
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}
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char in = uart_getc(UART_ID);
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printf("%c\n", in);
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}
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int main()
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{
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stdio_init_all();
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// Set up our UART for booting the other device
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uart_init(UART_ID, BAUD_RATE);
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gpio_set_function(UART_TX_PIN, GPIO_FUNC_UART);
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gpio_set_function(UART_RX_PIN, GPIO_FUNC_UART);
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// Set up run pin
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gpio_init(RUN_PIN);
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gpio_set_dir(RUN_PIN, GPIO_OUT);
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// Reset chip
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reset_chip();
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while (true) {
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char splash[] = "RP2350";
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char hello[] = "Hello";
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char buf[500] = {0};
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int i = 0;
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while (uart_is_readable(UART_ID) && i < sizeof(buf)) {
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char in = uart_getc(UART_ID);
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printf("%c", in);
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buf[i] = in;
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i++;
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}
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if (i > 0) {
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printf(" ...Read done\n");
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}
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char *ptr = memchr(buf, 'R', sizeof(buf));
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if (ptr && strncmp(ptr, splash, sizeof(splash) - 1) == 0) {
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printf("Splash found\n");
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uart_boot();
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} else {
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ptr = memchr(buf, 'H', sizeof(buf));
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if (ptr && strncmp(ptr, hello, sizeof(hello) - 1) == 0) {
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printf("Device is running\n");
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} else {
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printf("Device not running - attempting reset\n");
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reset_chip();
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}
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}
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sleep_ms(1000);
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}
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}

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