44 lines
1.1 KiB
C
44 lines
1.1 KiB
C
/**
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* BluettiCRC - CRC-16/MODBUS helpers for the Bluetti BLE protocol
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*
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* Ported from the Bluetti_ESP32_Bridge project (crc16.h / utils.cpp).
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* Polynomial 0xA001 (reversed 0x8005), initial value 0xFFFF.
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*
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* Copyright (c) 2026 Scott Penrose
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* License: MIT
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*/
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#ifndef BLUETTI_CRC_H
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#define BLUETTI_CRC_H
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#include <stdint.h>
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#include <stddef.h>
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// Update a running CRC-16/MODBUS with one byte.
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static inline uint16_t bluettiCrc16Update(uint16_t crc, uint8_t a) {
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crc ^= a;
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for (int i = 0; i < 8; ++i) {
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if (crc & 1)
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crc = (crc >> 1) ^ 0xA001;
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else
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crc = (crc >> 1);
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}
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return crc;
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}
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// CRC-16/MODBUS over a buffer (init 0xFFFF).
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static inline uint16_t bluettiModbusCrc(const uint8_t* buf, size_t len) {
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uint16_t crc = 0xFFFF;
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for (size_t i = 0; i < len; i++) {
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crc = bluettiCrc16Update(crc, buf[i]);
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}
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return crc;
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}
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// Swap the two bytes of a 16-bit value (used to place write values big-endian).
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static inline uint16_t bluettiSwapBytes(uint16_t v) {
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return (uint16_t)((v << 8) | (v >> 8));
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}
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#endif // BLUETTI_CRC_H
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