Мне необходимо написать функцию, которая использует справочную таблицу для значений АЦП для аналогового входа датчика температуры, и она определяет температуру по заданному значению АЦП путем "интерполяции" - линейного приближения.Я создал функцию и написал несколько тестовых примеров для нее, я хочу знать, есть ли что-то, что вы, ребята, можете предложить для улучшения кода, поскольку это должно быть для встроенного uC, вероятно, stm32.
Я публикую свой код и прикрепляю мой C-файл, он будет скомпилирован и запущен.
Пожалуйста, дайте мне знать, если у вас есть какие-либо комментарии / предложения по улучшению.
Я также хочу знатьНемного о приведении из uint32_t к float, которое я делаю, если это эффективный способ написания кода.
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#define TEMP_ADC_TABLE_SIZE 15
typedef struct
{
int8_t temp;
uint16_t ADC;
}Temp_ADC_t;
const Temp_ADC_t temp_ADC[TEMP_ADC_TABLE_SIZE] =
{
{-40,880}, {-30,750},
{-20,680}, {-10,595},
{0,500}, {10,450},
{20,410}, {30,396},
{40,390}, {50,386},
{60,375}, {70,360},
{80,340}, {90,325},
{100,310}
};
// This function finds the indices between which the input reading lies.
// It uses an algorithm that doesn't need to loop through all the values in the
// table but instead it keeps dividing the table in two half until it finds
// the indices between which the value is or the exact index.
//
// index_low, index_high, are set to the indices if a value is between sample
// points, otherwise if there is an exact match then index_mid is set.
//
// Returns 0 on error, 1 if indices found, 2 if exact index is found.
uint8_t find_indices(uint16_t ADC_reading,
const Temp_ADC_t table[],
int8_t dir,
uint16_t* index_low,
uint16_t* index_high,
uint16_t* index_mid,
uint16_t table_size)
{
uint8_t found = 0;
uint16_t mid, low, high;
low = 0;
high = table_size - 1;
if((table != NULL) && (table_size > 0) && (index_low != NULL) &&
(index_mid != NULL) && (index_high != NULL))
{
while(found == 0)
{
mid = (low + high) / 2;
if(table[mid].ADC == ADC_reading)
{
// exact match
found = 2;
}
else if(table[mid].ADC < ADC_reading)
{
if(table[mid + dir].ADC == ADC_reading)
{
// exact match
found = 2;
mid = mid + dir;
}
else if(table[mid + dir].ADC > ADC_reading)
{
// found the two indices
found = 1;
low = (dir == 1)? mid : (mid + dir);
high = (dir == 1)? (mid + dir) : mid;
}
else if(table[mid + dir].ADC < ADC_reading)
{
low = (dir == 1)? (mid + dir) : low;
high = (dir == 1) ? high : (mid + dir);
}
}
else if(table[mid].ADC > ADC_reading)
{
if(table[mid - dir].ADC == ADC_reading)
{
// exact match
found = 2;
mid = mid - dir;
}
else if(table[mid - dir].ADC < ADC_reading)
{
// found the two indices
found = 1;
low = (dir == 1)? (mid - dir) : mid;
high = (dir == 1)? mid : (mid - dir);
}
else if(table[mid - dir].ADC > ADC_reading)
{
low = (dir == 1)? low : (mid - dir);
high = (dir == 1) ? (mid - dir) : high;
}
}
}
*index_low = low;
*index_high = high;
*index_mid = mid;
}
return found;
}
// This function uses the lookup table provided as an input argument to find the
// temperature for a ADC value using linear approximation.
//
// Temperature value is set using the temp pointer.
//
// Return 0 if an error occured, 1 if an approximate result is calculate, 2
// if the sample value match is found.
uint8_t lookup_temp(uint16_t ADC_reading, const Temp_ADC_t table[],
uint16_t table_size ,int8_t* temp)
{
uint16_t mid, low, high;
int8_t dir;
uint8_t return_code = 1;
float gradient, offset;
low = 0;
high = table_size - 1;
if((table != NULL) && (temp != NULL) && (table_size > 0))
{
// Check if ADC_reading is out of bound and find if values are
// increasing or decreasing along the table.
if(table[low].ADC < table[high].ADC)
{
if(table[low].ADC > ADC_reading)
{
return_code = 0;
}
else if(table[high].ADC < ADC_reading)
{
return_code = 0;
}
dir = 1;
}
else
{
if(table[low].ADC < ADC_reading)
{
return_code = 0;
}
else if(table[high].ADC > ADC_reading)
{
return_code = 0;
}
dir = -1;
}
}
else
{
return_code = 0;
}
// determine the temperature by interpolating
if(return_code > 0)
{
return_code = find_indices(ADC_reading, table, dir, &low, &high, &mid,
table_size);
if(return_code == 2)
{
*temp = table[mid].temp;
}
else if(return_code == 1)
{
gradient = ((float)(table[high].temp - table[low].temp)) /
((float)(table[high].ADC - table[low].ADC));
offset = (float)table[low].temp - gradient * table[low].ADC;
*temp = (int8_t)(gradient * ADC_reading + offset);
}
}
return return_code;
}
int main(int argc, char *argv[])
{
int8_t temp = 0;
uint8_t x = 0;
uint16_t u = 0;
uint8_t return_code = 0;
uint8_t i;
//Print Table
printf("Lookup Table:\n");
for(i = 0; i < TEMP_ADC_TABLE_SIZE; i++)
{
printf("%d,%d\n", temp_ADC[i].temp, temp_ADC[i].ADC);
}
// Test case 1
printf("Test case 1: Find the temperature for ADC Reading of 317\n");
printf("Temperature should be 95 Return Code should be 1\n");
return_code = lookup_temp(317, temp_ADC, TEMP_ADC_TABLE_SIZE, &temp);
printf("Temperature: %d C\n", temp);
printf("Return code: %d\n\n", return_code);
// Test case 2
printf("Test case 2: Find the temperature for ADC Reading of 595 (sample value)\n");
printf("Temperature should be -10, Return Code should be 2\n");
return_code = lookup_temp(595, temp_ADC, TEMP_ADC_TABLE_SIZE, &temp);
printf("Temperature: %d C\n", temp);
printf("Return code: %d\n\n", return_code);
// Test case 3
printf("Test case 3: Find the temperature for ADC Reading of 900 (out of bound - lower)\n");
printf("Return Code should be 0\n");
return_code = lookup_temp(900, temp_ADC, TEMP_ADC_TABLE_SIZE, &temp);
printf("Return code: %d\n\n", return_code);
// Test case 4
printf("Test case 4: Find the temperature for ADC Reading of 300 (out of bound - Upper)\n");
printf("Return Code should be 0\n");
return_code = lookup_temp(300, temp_ADC, TEMP_ADC_TABLE_SIZE, &temp);
printf("Return code: %d\n\n", return_code);
// Test case 5
printf("Test case 5: NULL pointer (Table pointer) handling\n");
printf("Return Code should be 0\n");
return_code = lookup_temp(595, NULL, TEMP_ADC_TABLE_SIZE, &temp);
printf("Return code: %d\n\n", return_code);
// Test case 6
printf("Test case 6: NULL pointer (temperature result pointer) handling\n");
printf("Return Code should be 0\n");
return_code = lookup_temp(595, temp_ADC, TEMP_ADC_TABLE_SIZE, NULL);
printf("Return code: %d\n", return_code);
// Test case 7
printf("Test case 7: Find the temperature for ADC Reading of 620\n");
printf("Temperature should be -14 Return Code should be 1\n");
return_code = lookup_temp(630, temp_ADC, TEMP_ADC_TABLE_SIZE, &temp);
printf("Temperature: %d C\n", temp);
printf("Return code: %d\n\n", return_code);
// Test case 8
printf("Test case 8: Find the temperature for ADC Reading of 880 (First table element test)\n");
printf("Temperature should be -40 Return Code should be 2\n");
return_code = lookup_temp(880, temp_ADC, TEMP_ADC_TABLE_SIZE, &temp);
printf("Temperature: %d C\n", temp);
printf("Return code: %d\n\n", return_code);
// Test case 9
printf("Test case 9: Find the temperature for ADC Reading of 310 (Last table element test)\n");
printf("Temperature should be 100 Return Code should be 2\n");
return_code = lookup_temp(310, temp_ADC, TEMP_ADC_TABLE_SIZE, &temp);
printf("Temperature: %d C\n", temp);
printf("Return code: %d\n\n", return_code);
printf("Press ENTER to continue...\n");
getchar();
return 0;
}