Обратная инженерия Контрольная сумма ИК-кода ИКАО

Question

Я работаю над Panasonic AC Unit, который управляется дистанционным пультом . Пульт отправляет 12 bytes.

Первые 5 bytes всегда идентичны. Следующие 6 bytes соответствуют температуре, вентиляторам, функциям и другим параметрам кондиционера, которые я смог выяснить сам.

Последнее byte является контрольная сумма, который каким-то образом получается из первого 11 bytes (или от байта6 к 11)

Поскольку я повторно создать ИК-коды во время выполнения, мне нужно уметь вычислять контрольную сумму для этих пакетов. Я пробовал со многими стандартными алгоритмами контрольной суммы, ни один из них не дал значимых результатов.

Не могли бы вы помочь мне узнать функцию контрольной суммы , используемой для этого устройства?

---

Вот список пакетов, составленных 11 bytes заголовка + данных и 1 byte из контрольной суммы, что я был в состоянии захвата из устройства:

40 00 14 81 25 00 A0 65 00 00 00 26 
40 00 14 81 25 00 A0 68 00 00 07 30 
40 00 14 81 25 04 28 65 00 00 00 2A 
40 00 14 81 25 04 28 68 00 00 00 2D 
40 00 14 81 25 04 28 68 00 00 02 2F 
40 00 14 81 25 04 28 68 00 00 03 30 
40 00 14 81 25 04 28 68 00 00 04 31 
40 00 14 81 25 04 28 68 00 00 05 32 
40 00 14 81 25 04 28 68 00 00 07 34 
40 00 14 81 25 04 28 69 00 00 01 2F 
40 00 14 81 25 04 A0 68 00 00 07 34 
40 00 14 81 25 08 9A 68 00 00 07 41 
40 00 14 81 25 08 9C 68 00 00 07 43 
40 00 14 81 25 08 9E 68 00 00 07 45 
40 00 14 81 25 08 A0 68 00 00 00 31 
40 00 14 81 25 08 A0 68 00 00 01 32 
40 00 14 81 25 08 A0 68 00 00 02 33 
40 00 14 81 25 08 A0 68 00 00 03 34 
40 00 14 81 25 08 A0 68 00 00 07 38 
40 00 14 81 25 08 A2 68 00 00 07 3A 
40 00 14 81 25 08 A4 68 00 00 07 3C 
40 00 14 81 25 08 A6 68 00 00 07 3E 
40 00 14 81 25 08 A8 68 00 00 07 40 
40 00 14 81 25 08 AA 68 00 00 07 42 
40 00 14 81 25 08 AC 68 00 00 07 44 
40 00 14 81 25 08 AE 68 00 00 07 46 
40 00 14 81 25 09 A0 68 00 00 07 39 
40 00 14 81 25 0A A0 68 00 00 07 3A 
40 00 14 81 25 0C A0 68 00 00 07 3C 
40 00 14 81 25 40 18 65 00 00 00 29 
40 00 14 81 25 40 1A 65 00 00 00 2B 
40 00 14 81 25 40 1C 65 00 00 00 2D 
40 00 14 81 25 40 1E 65 00 00 00 2F 
40 00 14 81 25 40 20 65 00 00 00 22 
40 00 14 81 25 40 22 65 00 00 00 24 
40 00 14 81 25 40 24 65 00 00 00 26 
40 00 14 81 25 40 26 65 00 00 00 28 
40 00 14 81 25 40 28 65 00 00 00 2A 
40 00 14 81 25 40 2A 65 00 00 00 2C 
40 00 14 81 25 40 2C 65 00 00 00 2E 
40 00 14 81 25 40 2E 65 00 00 00 30 
40 00 14 81 25 40 30 65 00 00 00 23 
40 00 14 81 25 40 32 65 00 00 00 25 
40 00 14 81 25 40 34 65 00 00 00 27 
40 00 14 81 25 40 34 68 00 00 04 2E 
40 00 14 81 25 80 1C 68 00 00 00 34 
40 00 14 81 25 80 20 65 00 00 00 26 
40 00 14 81 25 C0 20 65 00 00 00 2A 
40 00 14 81 25 C0 28 68 00 00 02 37 

Answer 1

Я нашел кандидат контрольная сумма функции, которая соответствует всем ваших данных, но я думаю, что необходимы дальнейшие корректировки, потому что я подозреваю, что магическое число Я использую в зависимости от что-то еще, которое я не учитывал должным образом.

---

Это функция, что я был в состоянии перепроектировать:

uint8_t get_checksum(const uint8_t data[], const size_t size) 
{ 
    assert(data); 

    uint8_t checksum = 0; 

    for (size_t i = 0; i < size; ++i) 
    { 
     checksum += (data[i] >> 4) + (data[i] & 0x0f); 
    } 

    checksum -= 8; /* magic number */ 

    return checksum; 
}; 

Альтернативный вариант:

uint8_t get_checksum(const uint8_t data[], const size_t size) 
{ 
    assert(data); 

    uint8_t checksum = 0xF8; /* magic number */ 

    for (size_t i = 0; i < size; ++i) 
    { 
     checksum += (data[i] >> 4) + (data[i] & 0x0f); 
    } 

    return checksum; 
}; 

---

Пример:

#include<stdio.h> 
#include<stdint.h> 
#include<assert.h> 

uint8_t get_checksum(const uint8_t data[], const size_t size) 
{ 
    assert(data); 

    uint8_t checksum = 0xF8; /* magic number */ 

    for (size_t i = 0; i < size; ++i) 
    { 
     checksum += (data[i] >> 4) + (data[i] & 0x0f); 
    } 

    return checksum; 
}; 

int main() 
{ 
    const size_t xlen = 49; 
    const size_t ylen = 12; 
    uint8_t v[49][12] = { 
     {0x40,0x00,0x14,0x81,0x25,0x00,0xA0,0x65,0x00,0x00,0x00,0x26}, 
     {0x40,0x00,0x14,0x81,0x25,0x00,0xA0,0x68,0x00,0x00,0x07,0x30}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x65,0x00,0x00,0x00,0x2A}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x68,0x00,0x00,0x00,0x2D}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x68,0x00,0x00,0x02,0x2F}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x68,0x00,0x00,0x03,0x30}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x68,0x00,0x00,0x04,0x31}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x68,0x00,0x00,0x05,0x32}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x68,0x00,0x00,0x07,0x34}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0x28,0x69,0x00,0x00,0x01,0x2F}, 
     {0x40,0x00,0x14,0x81,0x25,0x04,0xA0,0x68,0x00,0x00,0x07,0x34}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0x9A,0x68,0x00,0x00,0x07,0x41}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0x9C,0x68,0x00,0x00,0x07,0x43}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0x9E,0x68,0x00,0x00,0x07,0x45}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA0,0x68,0x00,0x00,0x00,0x31}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA0,0x68,0x00,0x00,0x01,0x32}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA0,0x68,0x00,0x00,0x02,0x33}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA0,0x68,0x00,0x00,0x03,0x34}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA0,0x68,0x00,0x00,0x07,0x38}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA2,0x68,0x00,0x00,0x07,0x3A}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA4,0x68,0x00,0x00,0x07,0x3C}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA6,0x68,0x00,0x00,0x07,0x3E}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xA8,0x68,0x00,0x00,0x07,0x40}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xAA,0x68,0x00,0x00,0x07,0x42}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xAC,0x68,0x00,0x00,0x07,0x44}, 
     {0x40,0x00,0x14,0x81,0x25,0x08,0xAE,0x68,0x00,0x00,0x07,0x46}, 
     {0x40,0x00,0x14,0x81,0x25,0x09,0xA0,0x68,0x00,0x00,0x07,0x39}, 
     {0x40,0x00,0x14,0x81,0x25,0x0A,0xA0,0x68,0x00,0x00,0x07,0x3A}, 
     {0x40,0x00,0x14,0x81,0x25,0x0C,0xA0,0x68,0x00,0x00,0x07,0x3C}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x18,0x65,0x00,0x00,0x00,0x29}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x1A,0x65,0x00,0x00,0x00,0x2B}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x1C,0x65,0x00,0x00,0x00,0x2D}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x1E,0x65,0x00,0x00,0x00,0x2F}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x20,0x65,0x00,0x00,0x00,0x22}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x22,0x65,0x00,0x00,0x00,0x24}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x24,0x65,0x00,0x00,0x00,0x26}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x26,0x65,0x00,0x00,0x00,0x28}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x28,0x65,0x00,0x00,0x00,0x2A}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x2A,0x65,0x00,0x00,0x00,0x2C}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x2C,0x65,0x00,0x00,0x00,0x2E}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x2E,0x65,0x00,0x00,0x00,0x30}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x30,0x65,0x00,0x00,0x00,0x23}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x32,0x65,0x00,0x00,0x00,0x25}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x34,0x65,0x00,0x00,0x00,0x27}, 
     {0x40,0x00,0x14,0x81,0x25,0x40,0x34,0x68,0x00,0x00,0x04,0x2E}, 
     {0x40,0x00,0x14,0x81,0x25,0x80,0x1C,0x68,0x00,0x00,0x00,0x34}, 
     {0x40,0x00,0x14,0x81,0x25,0x80,0x20,0x65,0x00,0x00,0x00,0x26}, 
     {0x40,0x00,0x14,0x81,0x25,0xC0,0x20,0x65,0x00,0x00,0x00,0x2A}, 
     {0x40,0x00,0x14,0x81,0x25,0xC0,0x28,0x68,0x00,0x00,0x02,0x37} 
    }; 

    // packet has 11 bytes, 1 byte is for the checksum 
    for (size_t i = 0; i < xlen; ++i) 
    { 
     uint8_t checksum = get_checksum(v[i], 11); 

     printf("result: %02x -- should be: %02x -- %s\n", 
       checksum, v[i][ylen - 1], 
       (checksum - v[i][ylen - 1] == 0 ? "OK" : "ERROR")); 
    } 
} 

Выход:

result: 26 -- should be: 26 -- OK 
result: 30 -- should be: 30 -- OK 
result: 2a -- should be: 2a -- OK 
result: 2d -- should be: 2d -- OK 
result: 2f -- should be: 2f -- OK 
result: 30 -- should be: 30 -- OK 
result: 31 -- should be: 31 -- OK 
result: 32 -- should be: 32 -- OK 
result: 34 -- should be: 34 -- OK 
result: 2f -- should be: 2f -- OK 
result: 34 -- should be: 34 -- OK 
result: 41 -- should be: 41 -- OK 
result: 43 -- should be: 43 -- OK 
result: 45 -- should be: 45 -- OK 
result: 31 -- should be: 31 -- OK 
result: 32 -- should be: 32 -- OK 
result: 33 -- should be: 33 -- OK 
result: 34 -- should be: 34 -- OK 
result: 38 -- should be: 38 -- OK 
result: 3a -- should be: 3a -- OK 
result: 3c -- should be: 3c -- OK 
result: 3e -- should be: 3e -- OK 
result: 40 -- should be: 40 -- OK 
result: 42 -- should be: 42 -- OK 
result: 44 -- should be: 44 -- OK 
result: 46 -- should be: 46 -- OK 
result: 39 -- should be: 39 -- OK 
result: 3a -- should be: 3a -- OK 
result: 3c -- should be: 3c -- OK 
result: 29 -- should be: 29 -- OK 
result: 2b -- should be: 2b -- OK 
result: 2d -- should be: 2d -- OK 
result: 2f -- should be: 2f -- OK 
result: 22 -- should be: 22 -- OK 
result: 24 -- should be: 24 -- OK 
result: 26 -- should be: 26 -- OK 
result: 28 -- should be: 28 -- OK 
result: 2a -- should be: 2a -- OK 
result: 2c -- should be: 2c -- OK 
result: 2e -- should be: 2e -- OK 
result: 30 -- should be: 30 -- OK 
result: 23 -- should be: 23 -- OK 
result: 25 -- should be: 25 -- OK 
result: 27 -- should be: 27 -- OK 
result: 2e -- should be: 2e -- OK 
result: 34 -- should be: 34 -- OK 
result: 26 -- should be: 26 -- OK 
result: 2a -- should be: 2a -- OK 
result: 37 -- should be: 37 -- OK