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hshosesalkinium
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[ext] example for json usage added
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/*
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* Copyright (c) 2024, Henrik Hose
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*
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* This file is part of the modm project.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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#include <modm/board.hpp>
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#include <modm/debug/logger.hpp>
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#include <nlohmann-json/json.hpp>
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#undef MODM_LOG_LEVEL
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#define MODM_LOG_LEVEL modm::log::INFO
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// ----------------------------------------------------------------------------
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extern "C" const uint32_t __flash_reserved_start[];
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using json = nlohmann::json;
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constexpr auto max_flash_pages{256};
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namespace data
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{
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struct person
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{
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std::string name;
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float height;
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int age;
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auto
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operator<=>(const person&) const = default;
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};
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void
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to_json(json& j, const person& p)
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{
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j = json{{"name", p.name}, {"height", p.height}, {"age", p.age}};
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}
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void
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from_json(const json& j, person& p)
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{
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j.at("name").get_to(p.name);
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j.at("height").get_to(p.height);
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j.at("age").get_to(p.age);
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}
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} // namespace data
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int
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main()
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{
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Board::initialize();
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MODM_LOG_INFO << "\n\n+++++++++++++++++++++++++++" << modm::endl;
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MODM_LOG_INFO << "++ NLOHMANN JSON example ++" << modm::endl;
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MODM_LOG_INFO << "+++++++++++++++++++++++++++\n" << modm::endl;
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data::person alice_struct = {"Alice", 1.85, 80};
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json alice_json = alice_struct;
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// basic JSON character string usage
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{
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auto alice_json_string = alice_json.dump();
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// imagine that we transmit this string over some interface
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MODM_LOG_INFO << "JSON from struct is: " << alice_json_string.c_str() << modm::endl;
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// and now we can retrieve the struct from the json object
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json retrieved_alice_json = json::parse(alice_json_string);
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// JSON is fairly self-annotated, so we might not even need the original struct
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MODM_LOG_INFO << "\nRetrieved from string JSON has fields ... ";
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for (auto& [key, value] : retrieved_alice_json.items())
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{
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MODM_LOG_INFO << key.c_str() << ", ";
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}
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MODM_LOG_INFO << modm::endl;
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MODM_LOG_INFO.flush();
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// check if retrieved struct is same
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auto retrieved_alice_struct = retrieved_alice_json.template get<data::person>();
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if (retrieved_alice_struct == alice_struct)
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{
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MODM_LOG_INFO << "\nRetrieved from string and original struct are identical"
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<< modm::endl;
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}
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MODM_LOG_INFO.flush();
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}
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// basic binary JSON usage
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{
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// convert to BSON
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auto alice_binary = json::to_bson(alice_json);
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MODM_LOG_INFO << "\nBinary JSON (BSON): ";
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for (const auto& byte : alice_binary) { MODM_LOG_INFO.printf(" 0x%02x", byte); }
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MODM_LOG_INFO << modm::endl;
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// put BSON in reserved flash
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uint32_t err{0};
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const size_t page_start =
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Flash::getPage(reinterpret_cast<uint32_t>(&__flash_reserved_start));
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const size_t num_bytes = alice_binary.size();
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const size_t flash_page_size = Flash::getSize(page_start);
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const size_t end_page = page_start + (num_bytes + flash_page_size - 1) / flash_page_size;
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if (end_page >= max_flash_pages)
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{
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MODM_LOG_ERROR << "\nRequested flash end page exceeds flash [" << page_start << ", "
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<< end_page << ")" << modm::endl;
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MODM_LOG_ERROR.flush();
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while (1)
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;
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}
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// erase the pages before programming
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MODM_LOG_INFO << "\nErasing flash sectors [" << page_start << ", " << end_page << ")"
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<< modm::endl;
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MODM_LOG_INFO.flush();
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if (not Flash::unlock())
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{
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MODM_LOG_ERROR << "Flash unlock failed!" << modm::endl;
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while (1)
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;
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}
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for (size_t page{page_start}; page < end_page; page++) err |= Flash::erase(page);
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if (err != 0)
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{
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MODM_LOG_ERROR << "\nThere was an error while erasing flash!" << modm::endl;
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MODM_LOG_ERROR.flush();
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while (1)
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;
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}
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// pad the data with zeros to fit flash words
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size_t unpadded_size{alice_binary.size()};
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size_t word_size{sizeof(Flash::MaxWordType)};
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if (auto padding = (word_size - unpadded_size % word_size) % word_size; padding > 0)
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{
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alice_binary.resize(alice_binary.size() + padding, 0);
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}
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// now, write the padded data
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MODM_LOG_INFO << "\nWriting, word size: " << word_size
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<< ", num of bytes (payload): " << unpadded_size
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<< ", num of bytes (padded): " << alice_binary.size() << "... ";
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const auto flash_write_base_addr{reinterpret_cast<uint32_t>(Flash::getAddr(page_start))};
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for (size_t ii = 0; ii < alice_binary.size(); ii += sizeof(Flash::MaxWordType))
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{
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Flash::MaxWordType outdata;
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memcpy(&outdata, &alice_binary[ii], sizeof(Flash::MaxWordType));
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err |= Flash::program(flash_write_base_addr + ii, outdata);
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}
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if (err != 0)
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{
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MODM_LOG_ERROR << "\nThere was an error while programming flash!" << modm::endl;
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MODM_LOG_ERROR.flush();
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while (1)
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;
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}
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MODM_LOG_INFO << "Writing complete! " << modm::endl;
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MODM_LOG_INFO.flush();
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// we can now read BSON back from flash, first 4 bytes entry is the size
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uint32_t read_len;
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memcpy(&read_len, Flash::getAddr(page_start), sizeof(read_len));
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// read the actual data
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MODM_LOG_INFO << "\nReading BSON of size " << read_len << " from flash: ";
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auto raw_bytes =
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std::vector<uint8_t>(Flash::getAddr(page_start), Flash::getAddr(page_start) + read_len);
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for (const auto& byte : raw_bytes) { MODM_LOG_INFO.printf(" 0x%02x", byte); }
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MODM_LOG_INFO << modm::endl;
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MODM_LOG_INFO.flush();
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// reconstruct the data
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auto retrieved_alice_json = json::from_bson(raw_bytes);
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auto retrieved_alice_struct = retrieved_alice_json.template get<data::person>();
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if (retrieved_alice_struct == alice_struct)
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{
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MODM_LOG_INFO << "\nRetrieved from flash and original struct are identical"
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<< modm::endl;
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MODM_LOG_INFO.flush();
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}
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}
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while (1)
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;
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return 0;
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}
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<library>
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<extends>modm:nucleo-g474re</extends>
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<options>
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<option name="modm:build:build.path">../../../build/nucleo_g474re/flash_json</option>
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<option name="modm:platform:cortex-m:linkerscript.flash_reserved">1024*16</option>
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</options>
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<modules>
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<module>modm:debug</module>
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<module>modm:platform:gpio</module>
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<module>modm:platform:flash</module>
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<module>modm:nlohmann-json</module>
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<module>modm:build:scons</module>
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</modules>
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</library>

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