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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"STM32H7x option_write reads incorrect address in flash","articleBody":"A recently added support for STM32H7R/H7Sx MCUs (https://github.com/STMicroelectronics/OpenOCD/commit/aa109db19ffd22eb05e18b010140fb562934533b) broke `stm32h7x option_write` command on STM32H757BIT6. I tested `stm32h7x option_write` command with 3 different commits:\n\n- Most recent commit - https://github.com/STMicroelectronics/OpenOCD/commit/0a084c29345576911fb8d10fcbd158d0361b6186\n- Added support for STM32H7R/H7Sx - https://github.com/STMicroelectronics/OpenOCD/commit/aa109db19ffd22eb05e18b010140fb562934533b\n- One commit prior to adding support for STM32H7R/H7Sx - https://github.com/STMicroelectronics/OpenOCD/commit/b62cbc2e853189e730fd94e6d9c0a1d3ceb2661f\n\n# Hardware\n\n- STM32H757BIT6 - dual core\n- STLINK-V3MINIE\n\n# Software\nOpenOCD is running in a Docker container:\n```\nRUN git clone https://github.com/STMicroelectronics/OpenOCD.git \u0026\u0026 \\\n    cd OpenOCD \u0026\u0026 \\\n    git checkout insert_git_commit_here \u0026\u0026 \\\n    ./bootstrap \u0026\u0026 \\\n    ./configure --enable-stlink \u0026\u0026 \\\n    make -j$(nproc) \u0026\u0026 \\\n    make install \u0026\u0026 \\\n    cd .. \u0026\u0026 \\\n    rm -rf OpenOCD\n```\n\nI am running OpenOCD with the following command\n`openocd -f openocd_stm32h757.cfg`\n\nI am connecting to the OpenOCD with telnet\n`telnet 127.0.0.1 4444`\n\n### Configuration file:\n```\n# openocd_stm32h757.cfg\nsource [find interface/stlink-dap.cfg]\ntransport select dapdirect_swd\nsource [find target/stm32h7x_dual_bank.cfg]\nreset_config srst_only \n```\n\n# Test results\n\nI tried disabling booting of CM4 by changing option byte FLASH_OPTSR_PRG and also tried `stm32h7x option_write` example in the [OpenOCD documentation section 12.5.2](https://openocd.org/doc/pdf/openocd.pdf). The output of the commands tested with different commits are shown in a table below. Only commit b62cbc2 produced expected results and wrote the option byte.\n\n| Command | Most recent https://github.com/STMicroelectronics/OpenOCD/commit/0a084c29345576911fb8d10fcbd158d0361b6186 | STM32H7R/H7Sx support https://github.com/STMicroelectronics/OpenOCD/commit/aa109db19ffd22eb05e18b010140fb562934533b | Prior to adding support https://github.com/STMicroelectronics/OpenOCD/commit/b62cbc2e853189e730fd94e6d9c0a1d3ceb2661f |\n| ------------- | ------------- | ------------- | ------------- |\n| reset | - | - | - |\n| stm32h7x option_read 0 0x1c | Option Register: \u003c0x5200201c\u003e = 0x1bc6aaf0 | Option Register: \u003c0x5200201c\u003e = 0x1bc6aaf0 | Option Register: \u003c0x5200201c\u003e = 0x1bc6aaf0 |\n| stm32h7x option_write 0 0x20 0x00000000 0x00400000 | Failed to read memory at 0x51e3be78 \u003cbr\u003e error while reading from address 0x51e3be78 | Failed to read memory at 0xe000edf4 \u003cbr\u003e error while reading from address 0x856d9473 | - |\n| stm32h7x option_read 0 0x1c | Option Register: \u003c0x5200201c\u003e = 0x1bc6aaf0 | Option Register: \u003c0x5200201c\u003e = 0x1bc6aaf0 | Option Register: \u003c0x5200201c\u003e = 0x1b86aaf0 |\n| stm32h7x option_write 0 0x20 0x8000000 0x8000000 | Failed to read memory at 0x51e3be78 \u003cbr\u003e error while reading from address 0x51e3be78 | Failed to read memory at 0xe000edf4 \u003cbr\u003e error while reading from address 0x856d9473 | - |\n| stm32h7x option_read 0 0x1c | Option Register: \u003c0x5200201c\u003e = 0x1bc6aaf0 | Option Register: \u003c0x5200201c\u003e = 0x1bc6aaf0 | Option Register: \u003c0x5200201c\u003e = 0x1b86aaf0 |\n\n# Observations\n\nDifferent functions are used in `src/flash/nor/stm32h7x.c` for reading values for commands `option_read` and `option_write`.\n\n| commit | OpenOCD command | function in stm32h7x.c |\n| ------------- | ------------- | ------------- |\n| aa109db | stm32h7x option_read | stm32x_read_flash_reg |\n| aa109db | stm32h7x option_write | stm32h7_read_flash_reg_by_index |\n| b310b3b | stm32h7x option_read | stm32x_read_flash_reg |\n| b310b3b | stm32h7x option_write | stm32x_read_flash_reg |\n\n# Conclusion\n\nIt seems function `stm32h7_read_flash_reg_by_index` in `src/flash/nor/stm32h7x.c` used in `option_write` command reads incorrect address from flash.\n\nThanks in advance!","author":{"url":"https://github.com/novakmichalinfo","@type":"Person","name":"novakmichalinfo"},"datePublished":"2026-01-13T13:57:45.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/45/OpenOCD/issues/45"}