Add simple UART bootloader

The sample binary flashes the LED and prints Hello, world back over the UART interface

README.md

@@ -44,6 +44,7 @@ App|Description
 App|Description
 ---|---
 [enc_bootloader](bootloaders/encrypted) | A bootloader which decrypts binaries from flash into SRAM. See the separate [README](bootloaders/encrypted/README.md) for more information
+[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
 
 ### Clocks
 

bootloaders/CMakeLists.txt

@@ -1,3 +1,5 @@
+add_subdirectory_exclude_platforms(uart host rp2040)
+
 if (TARGET pico_mbedtls)
     add_subdirectory_exclude_platforms(encrypted host rp2040 rp2350-riscv)
 else()

bootloaders/uart/CMakeLists.txt

@@ -0,0 +1,32 @@
+add_executable(uart_boot
+    uart_boot.c
+    )
+
+# pull in common dependencies
+target_link_libraries(uart_boot pico_stdlib hardware_flash)
+
+pico_embed_pt_in_binary(uart_boot ${CMAKE_CURRENT_LIST_DIR}/uart-pt.json)
+pico_set_uf2_family(uart_boot "absolute")
+
+# create map/bin/hex file etc.
+pico_add_extra_outputs(uart_boot)
+
+# add url via pico_set_program_url
+example_auto_set_url(uart_boot)
+
+
+add_executable(uart_binary
+    uart_binary.c
+    )
+
+# pull in common dependencies
+target_link_libraries(uart_binary pico_stdlib)
+
+pico_set_binary_type(uart_binary no_flash)
+pico_package_uf2_output(uart_binary 0x10000000)
+
+# create map/bin/hex/uf2 file etc.
+pico_add_extra_outputs(uart_binary)
+
+# call pico_set_program_url to set path to example on github, so users can find the source for an example via picotool
+example_auto_set_url(uart_binary)

bootloaders/uart/uart-pt.json

@@ -0,0 +1,23 @@
+{
+  "version": [1, 0],
+  "unpartitioned": {
+    "families": ["absolute"],
+    "permissions": {
+      "secure": "rw",
+      "nonsecure": "rw",
+      "bootloader": "rw"
+    }
+  },
+  "partitions": [
+    {
+      "start": "128K",
+      "size": "32K",
+      "families": ["rp2350-arm-s"],
+      "permissions": {
+        "secure": "rw",
+        "nonsecure": "rw",
+        "bootloader": "rw"
+      }
+    }
+  ]
+}

bootloaders/uart/uart_binary.c

@@ -0,0 +1,65 @@
+/**
+ * Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include "pico/stdlib.h"
+#include "hardware/uart.h"
+#include "hardware/structs/pads_qspi.h"
+#include "hardware/structs/io_qspi.h"
+
+#ifndef LED_DELAY_MS
+#define LED_DELAY_MS 500
+#endif
+
+// Initialize the GPIO for the LED
+void pico_led_init(void) {
+#ifdef PICO_DEFAULT_LED_PIN
+    // A device like Pico that uses a GPIO for the LED will define PICO_DEFAULT_LED_PIN
+    // so we can use normal GPIO functionality to turn the led on and off
+    gpio_init(PICO_DEFAULT_LED_PIN);
+    gpio_set_dir(PICO_DEFAULT_LED_PIN, GPIO_OUT);
+#endif
+}
+
+// Turn the LED on or off
+void pico_set_led(bool led_on) {
+#if defined(PICO_DEFAULT_LED_PIN)
+    // Just set the GPIO on or off
+    gpio_put(PICO_DEFAULT_LED_PIN, led_on);
+#endif
+}
+
+// Set function for QSPI GPIO pin
+void qspi_gpio_set_function(uint gpio, gpio_function_t fn) {
+    // Set input enable on, output disable off
+    hw_write_masked(&pads_qspi_hw->io[gpio],
+                   PADS_QSPI_GPIO_QSPI_SD2_IE_BITS,
+                   PADS_QSPI_GPIO_QSPI_SD2_IE_BITS | PADS_QSPI_GPIO_QSPI_SD2_OD_BITS
+    );
+    // Zero all fields apart from fsel; we want this IO to do what the peripheral tells it.
+    // This doesn't affect e.g. pullup/pulldown, as these are in pad controls.
+    io_qspi_hw->io[gpio].ctrl = fn << IO_QSPI_GPIO_QSPI_SD2_CTRL_FUNCSEL_LSB;
+
+    // Remove pad isolation now that the correct peripheral is in control of the pad
+    hw_clear_bits(&pads_qspi_hw->io[gpio], PADS_QSPI_GPIO_QSPI_SD2_ISO_BITS);
+}
+
+int main() {
+    pico_led_init();
+
+    // SD2 is QSPI GPIO 3, SD3 is QSPI GPIO 4
+    qspi_gpio_set_function(3, GPIO_FUNC_UART_AUX);
+    qspi_gpio_set_function(4, GPIO_FUNC_UART_AUX);
+
+    uart_init(uart0, 1000000);
+
+    while (true) {
+        uart_puts(uart0, "Hello, world\n");
+        pico_set_led(true);
+        sleep_ms(LED_DELAY_MS);
+        pico_set_led(false);
+        sleep_ms(LED_DELAY_MS);
+    }
+}

bootloaders/uart/uart_boot.c

@@ -0,0 +1,152 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "pico/stdlib.h"
+#include "hardware/uart.h"
+#include "pico/bootrom.h"
+#include "boot/picobin.h"
+#include "hardware/flash.h"
+
+// UART defines for uart boot
+#define UART_ID uart1
+#define BAUD_RATE 1000000
+
+// Use pins 4 and 5 for uart boot
+#define UART_TX_PIN 4
+#define UART_RX_PIN 5
+
+// Use pin 3 for the RUN pin on the other chip
+#define RUN_PIN 3
+
+
+void reset_chip() {
+    // Toggle run pin
+    gpio_put(RUN_PIN, false);
+    sleep_ms(1);
+    gpio_put(RUN_PIN, true);
+}
+
+
+void uart_boot() {
+    uint knocks = 0;
+    while (true) {
+        // Send the knock sequence
+        uart_putc_raw(UART_ID, 0x56);
+        uart_putc_raw(UART_ID, 0xff);
+        uart_putc_raw(UART_ID, 0x8b);
+        uart_putc_raw(UART_ID, 0xe4);
+        uart_putc_raw(UART_ID, 'n');
+
+        if (uart_is_readable_within_us(UART_ID, 1000)) {
+            char in = uart_getc(UART_ID);
+            printf("%c\n", in);
+            break;
+        } else {
+            if (knocks > 10) {
+                printf("No response - resetting\n");    
+                reset_chip();
+                return;
+            }
+            printf("No response - knocking again\n");
+            knocks++;
+        }
+    }
+
+    printf("Boot starting\n");
+
+    // Get partition location in flash
+    const int buf_words = (16 * 4) + 1;   // maximum of 16 partitions, each with maximum of 4 words returned, plus 1
+    uint32_t* buffer = malloc(buf_words * 4);
+
+    int ret = rom_get_partition_table_info(buffer, buf_words, PT_INFO_PARTITION_LOCATION_AND_FLAGS | PT_INFO_SINGLE_PARTITION | (0 << 24));
+    assert(buffer[0] == (PT_INFO_PARTITION_LOCATION_AND_FLAGS | PT_INFO_SINGLE_PARTITION));
+    assert(ret == 3);
+
+    uint32_t location_and_permissions = buffer[1];
+    uint32_t saddr = XIP_BASE + ((location_and_permissions >> PICOBIN_PARTITION_LOCATION_FIRST_SECTOR_LSB) & 0x1fffu) * FLASH_SECTOR_SIZE;
+    uint32_t eaddr = XIP_BASE + (((location_and_permissions >> PICOBIN_PARTITION_LOCATION_LAST_SECTOR_LSB) & 0x1fffu) + 1) * FLASH_SECTOR_SIZE;
+    printf("Start %08x, end %08x\n", saddr, eaddr);
+
+    free(buffer);
+
+    printf("Writing binary\n");
+    uint32_t tstart = time_us_32();
+    uint32_t caddr = saddr;
+    while (caddr < eaddr) {
+        uart_putc_raw(UART_ID, 'w');
+        char *buf = (char*)caddr;
+        for (int i=0; i < 32; i++) {
+            uart_putc_raw(UART_ID, buf[i]);
+        }
+        if (!uart_is_readable_within_us(UART_ID, 500)) {
+            // Detect hangs and reset the chip
+            printf("Write has hung - resetting\n");
+            reset_chip();
+            return;
+        }
+        char in = uart_getc(UART_ID);
+        printf("%c\n", in);
+        caddr += 32;
+    }
+
+    uint32_t tend = time_us_32();
+    printf("Write took %dus\n", tend - tstart);
+    printf("Write complete - executing\n");
+    uart_putc_raw(UART_ID, 'x');
+    if (!uart_is_readable_within_us(UART_ID, 500)) {
+        // Detect hangs and reset the chip
+        printf("Execute has hung - resetting\n");
+        reset_chip();
+        return;
+    }
+    char in = uart_getc(UART_ID);
+    printf("%c\n", in);
+}
+
+
+int main()
+{
+    stdio_init_all();
+
+    // Set up our UART for booting the other device
+    uart_init(UART_ID, BAUD_RATE);
+    gpio_set_function(UART_TX_PIN, GPIO_FUNC_UART);
+    gpio_set_function(UART_RX_PIN, GPIO_FUNC_UART);
+
+    // Set up run pin
+    gpio_init(RUN_PIN);
+    gpio_set_dir(RUN_PIN, GPIO_OUT);
+
+    // Reset chip
+    reset_chip();
+
+
+    while (true) {
+        char splash[] = "RP2350";
+        char hello[] = "Hello";
+        char buf[500] = {0};
+        int i = 0;
+        while (uart_is_readable(UART_ID) && i < sizeof(buf)) {
+            char in = uart_getc(UART_ID);
+            printf("%c", in);
+            buf[i] = in;
+            i++;
+        }
+        if (i > 0) {
+            printf(" ...Read done\n");
+        }
+        char *ptr = memchr(buf, 'R', sizeof(buf));
+        if (ptr && strncmp(ptr, splash, sizeof(splash) - 1) == 0) {
+            printf("Splash found\n");
+            uart_boot();
+        } else {
+            ptr = memchr(buf, 'H', sizeof(buf));
+            if (ptr && strncmp(ptr, hello, sizeof(hello) - 1) == 0) {
+                printf("Device is running\n");
+            } else {
+                printf("Device not running - attempting reset\n");
+                reset_chip();
+            }
+        }
+        sleep_ms(1000);
+    }
+}