void flash_range_erase (uint32_t flash_offs, size_t count)
 Erase areas of flash. More...
void flash_range_program (uint32_t flash_offs, const uint8_t *data, size_t count)
 Program flash. More...
void flash_get_unique_id (uint8_t *id_out)
 Get flash unique 64 bit identifier. More...
void flash_do_cmd (const uint8_t *txbuf, uint8_t *rxbuf, size_t count)
 Execute bidirectional flash command. More...

Detailed Description

Low level flash programming and erase API

Note these functions are unsafe if you have two cores concurrently executing from flash. In this case you must perform your own synchronisation to make sure no XIP accesses take place during flash programming.

Likewise they are unsafe if you have interrupt handlers or an interrupt vector table in flash, so you must disable interrupts before calling in this case.

If PICO_NO_FLASH=1 is not defined (i.e. if the program is built to run from flash) then these functions will make a static copy of the second stage bootloader in SRAM, and use this to reenter execute-in-place mode after programming or erasing flash, so that they can safely be called from flash-resident code.


#include <stdio.h>
#include <stdlib.h>
#include "pico/stdlib.h"
#include "hardware/flash.h"
// We're going to erase and reprogram a region 256k from the start of flash.
// Once done, we can access this at XIP_BASE + 256k.
#define FLASH_TARGET_OFFSET (256 * 1024)
const uint8_t *flash_target_contents = (const uint8_t *) (XIP_BASE + FLASH_TARGET_OFFSET);
void print_buf(const uint8_t *buf, size_t len) {
for (size_t i = 0; i < len; ++i) {
printf("%02x", buf[i]);
if (i % 16 == 15)
printf(" ");
int main() {
uint8_t random_data[FLASH_PAGE_SIZE];
for (int i = 0; i < FLASH_PAGE_SIZE; ++i)
random_data[i] = rand() >> 16;
printf("Generated random data:\n");
print_buf(random_data, FLASH_PAGE_SIZE);
// Note that a whole number of sectors must be erased at a time.
printf("\nErasing target region...\n");
printf("Done. Read back target region:\n");
print_buf(flash_target_contents, FLASH_PAGE_SIZE);
printf("\nProgramming target region...\n");
flash_range_program(FLASH_TARGET_OFFSET, random_data, FLASH_PAGE_SIZE);
printf("Done. Read back target region:\n");
print_buf(flash_target_contents, FLASH_PAGE_SIZE);
bool mismatch = false;
for (int i = 0; i < FLASH_PAGE_SIZE; ++i) {
if (random_data[i] != flash_target_contents[i])
mismatch = true;
if (mismatch)
printf("Programming failed!\n");
printf("Programming successful!\n");
void __no_inline_not_in_flash_func() flash_range_program(uint32_t flash_offs, const uint8_t *data, size_t count)
Program flash.
Definition: flash.c:86
void __no_inline_not_in_flash_func() flash_range_erase(uint32_t flash_offs, size_t count)
Erase areas of flash.
Definition: flash.c:63
void stdio_init_all(void)
Initialize all of the present standard stdio types that are linked into the binary.
Definition: stdio.c:270

Function Documentation

◆ flash_do_cmd()

void flash_do_cmd ( const uint8_t *  txbuf,
uint8_t *  rxbuf,
size_t  count 

Execute bidirectional flash command.

Low-level function to execute a serial command on a flash device attached to the QSPI interface. Bytes are simultaneously transmitted and received from txbuf and to rxbuf. Therefore, both buffers must be the same length, count, which is the length of the overall transaction. This is useful for reading metadata from the flash chip, such as device ID or SFDP parameters.

The XIP cache is flushed following each command, in case flash state has been modified. Like other hardware_flash functions, the flash is not accessible for execute-in-place transfers whilst the command is in progress, so entering a flash-resident interrupt handler or executing flash code on the second core concurrently will be fatal. To avoid these pitfalls it is recommended that this function only be used to extract flash metadata during startup, before the main application begins to run: see the implementation of pico_get_unique_id() for an example of this.

txbufPointer to a byte buffer which will be transmitted to the flash
rxbufPointer to a byte buffer where data received from the flash will be written. txbuf and rxbuf may be the same buffer.
countLength in bytes of txbuf and of rxbuf

◆ flash_get_unique_id()

void flash_get_unique_id ( uint8_t *  id_out)

Get flash unique 64 bit identifier.

Use a standard 4Bh RUID instruction to retrieve the 64 bit unique identifier from a flash device attached to the QSPI interface. Since there is a 1:1 association between the MCU and this flash, this also serves as a unique identifier for the board.

id_outPointer to an 8-byte buffer to which the ID will be written

◆ flash_range_erase()

void flash_range_erase ( uint32_t  flash_offs,
size_t  count 

Erase areas of flash.

flash_offsOffset into flash, in bytes, to start the erase. Must be aligned to a 4096-byte flash sector.
countNumber of bytes to be erased. Must be a multiple of 4096 bytes (one sector).

◆ flash_range_program()

void flash_range_program ( uint32_t  flash_offs,
const uint8_t *  data,
size_t  count 

Program flash.

flash_offsFlash address of the first byte to be programmed. Must be aligned to a 256-byte flash page.
dataPointer to the data to program into flash
countNumber of bytes to program. Must be a multiple of 256 bytes (one page).