/** * Copyright (c) 2020 Raspberry Pi (Trading) Ltd. * * SPDX-License-Identifier: BSD-3-Clause */ #include <stdio.h> #include "pico/stdlib.h" #include "pico/bootrom.h" #include "hardware/structs/otp.h" int main() { stdio_init_all(); otp_cmd_t cmd; int8_t ret; // Row to write ECC data uint16_t ecc_row = 0x400; // Row to write raw data uint16_t raw_row = 0x410; // Check rows are empty - else the rest of the tests won't behave as expected unsigned char initial_data[32] = {0}; cmd.flags = ecc_row; ret = rom_func_otp_access(initial_data, sizeof(initial_data)/2, cmd); if (ret) { printf("ERROR: Initial ECC Row Read failed with error %d\n", ret); } cmd.flags = raw_row; ret = rom_func_otp_access(initial_data+(sizeof(initial_data)/2), sizeof(initial_data)/2, cmd); if (ret) { printf("ERROR: Initial Raw Row Read failed with error %d\n", ret); } for (int i=0; i < sizeof(initial_data); i++) { if (initial_data[i] != 0) { printf("ERROR: This example requires empty OTP rows to run - change the ecc_row and raw_row variables to an empty row and recompile\n"); return 0; } } if (ecc_row) { // Write an ECC value to OTP - the buffer must have a multiple of 2 length for ECC data unsigned char ecc_write_data[16] = "Hello from OTP"; cmd.flags = ecc_row | OTP_CMD_ECC_BITS | OTP_CMD_WRITE_BITS; ret = rom_func_otp_access(ecc_write_data, sizeof(ecc_write_data), cmd); if (ret) { printf("ERROR: ECC Write failed with error %d\n", ret); } else { printf("ECC Write succeeded\n"); } // Read it back unsigned char ecc_read_data[sizeof(ecc_write_data)] = {0}; cmd.flags = ecc_row | OTP_CMD_ECC_BITS; ret = rom_func_otp_access(ecc_read_data, sizeof(ecc_read_data), cmd); if (ret) { printf("ERROR: ECC Read failed with error %d\n", ret); } else { printf("ECC Data read is \"%s\"\n", ecc_read_data); } // Set some bits, to demonstrate ECC error correction unsigned char ecc_toggle_buffer[sizeof(ecc_write_data)*2] = {0}; cmd.flags = ecc_row; ret = rom_func_otp_access(ecc_toggle_buffer, sizeof(ecc_toggle_buffer), cmd); if (ret) { printf("ERROR: Raw read of ECC data failed with error %d\n", ret); } else { ecc_toggle_buffer[0] = 'x'; // will fail to recover, as flips 2 bits from 'H' (100_1000 -> 111_1000) ecc_toggle_buffer[24] = 't'; // will recover, as only flips 1 bit from 'T' (101_0100 -> 111_0100) cmd.flags = ecc_row | OTP_CMD_WRITE_BITS; ret = rom_func_otp_access(ecc_toggle_buffer, sizeof(ecc_toggle_buffer), cmd); if (ret) { printf("ERROR: Raw overwrite of ECC data failed with error %d\n", ret); } else { printf("Raw overwrite of ECC data succeeded\n"); } } // Read it back unsigned char ecc_toggled_read_data[sizeof(ecc_write_data)] = {0}; cmd.flags = ecc_row | OTP_CMD_ECC_BITS; ret = rom_func_otp_access(ecc_toggled_read_data, sizeof(ecc_toggled_read_data), cmd); if (ret) { printf("ERROR: ECC Read failed with error %d\n", ret); } else { printf("ECC Data read is now \"%s\"\n", ecc_toggled_read_data); } // Attempt to write a different ECC value to OTP - should fail unsigned char ecc_overwrite_data[sizeof(ecc_write_data)] = "hello from otp"; cmd.flags = ecc_row | OTP_CMD_ECC_BITS | OTP_CMD_WRITE_BITS; ret = rom_func_otp_access(ecc_overwrite_data, sizeof(ecc_overwrite_data), cmd); if (ret == BOOTROM_ERROR_UNSUPPORTED_MODIFICATION) { printf("Overwrite of ECC data failed as expected\n"); } else { printf("ERROR: "); if (ret) { printf("Overwrite failed with error %d\n", ret); } else { printf("Overwrite succeeded\n"); } } } if (raw_row) { // Write a raw value to OTP - the buffer must have a multiple of 4 length for raw data // Each row only holds 24 bits, so every 4th byte isn't written to OTP unsigned char raw_write_data[20] = "Hel\0lo \0fro\0m O\0TP"; cmd.flags = raw_row | OTP_CMD_WRITE_BITS; ret = rom_func_otp_access(raw_write_data, sizeof(raw_write_data), cmd); if (ret) { printf("ERROR: Raw Write failed with error %d\n", ret); } else { printf("Raw Write succeeded\n"); } // Read it back unsigned char raw_read_data[sizeof(raw_write_data)] = {0}; cmd.flags = raw_row; ret = rom_func_otp_access(raw_read_data, sizeof(raw_read_data), cmd); if (ret) { printf("ERROR: Raw Read failed with error %d\n", ret); } else { // Remove the null bytes for (int i=0; i < sizeof(raw_read_data)/4; i++) { memcpy(raw_read_data + i*3, raw_read_data + i*4, 3); } printf("Raw Data read is \"%s\"\n", raw_read_data); } // Attempt to write a different raw value to OTP - should succeed, provided no bits are cleared // This can be done by using '~' for even characters, and 'o' for odd ones unsigned char raw_overwrite_data[sizeof(raw_write_data)] = {0}; for (int i=0; i < sizeof(raw_write_data); i++) { if (raw_write_data[i]) { raw_overwrite_data[i] = (raw_write_data[i] % 2) ? 'o' : '~'; } else { raw_overwrite_data[i] = 0; } } cmd.flags = raw_row | OTP_CMD_WRITE_BITS; ret = rom_func_otp_access(raw_overwrite_data, sizeof(raw_overwrite_data), cmd); if (ret) { printf("ERROR: Raw Overwrite failed with error %d\n", ret); } else { printf("Raw Overwrite succeeded\n"); } // Read it back unsigned char raw_read_data_again[sizeof(raw_write_data)] = {0}; cmd.flags = raw_row; ret = rom_func_otp_access(raw_read_data_again, sizeof(raw_read_data_again), cmd); // Remove the null bytes for (int i=0; i < sizeof(raw_read_data_again)/4; i++) { memcpy(raw_read_data_again + i*3, raw_read_data_again + i*4, 3); } if (ret) { printf("ERROR: Raw Read failed with error %d\n", ret); } else { printf("Raw Data read is now \"%s\"\n", raw_read_data_again); } } int16_t lock_row = ecc_row ? ecc_row : raw_row; // Lock the OTP page, to prevent any more reads or writes until the next reset int page = lock_row / 0x40; otp_hw->sw_lock[page] = 0xf; printf("OTP Software Lock Done\n"); // Attempt to read it back again - should fail unsigned char read_data_locked[8] = {0}; cmd.flags = lock_row | (lock_row == ecc_row ? OTP_CMD_ECC_BITS : 0); ret = rom_func_otp_access(read_data_locked, sizeof(read_data_locked), cmd); if (ret == BOOTROM_ERROR_NOT_PERMITTED) { printf("Locked read failed as expected\n"); } else { printf("ERROR: "); if (ret) { printf("Locked read failed with error %d\n", ret); } else { printf("Locked read succeeded. Data read is \"%s\"\n", read_data_locked); } } return 0; }

This firmware image was imported from the pico-examples repository. 


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