我有一个基于我需要在C中实现的ADC（模拟 - 数字转换器）计数范围来计算温度的表。我不知道如何这样做，因为它不会是精确的值，它将处于重叠范围内。
代码将从传感器读取ADC值整数值（第2-4列分别表示ADC低电平，ADC中心电压和ADC高电平）并吐出温度（第1列）。这些值来自我从电阻到电压转换为ADC的文档。 ADC值将是一个整数，并且它必须是该范围内的最佳拟合，我认为这意味着最接近中心值。它不需要非常精确，因为它是一个非常稳定的值（通常在370-350之间，也就是25-26C），它将用于确定过热（41C）。
以下是该表格中几个单元格的示例：
Temperature | ADC Low | ADC Center | ADC High
-------------+-------------+-------------+------------
25 | 362.1804923 | 372.3636364 | 382.4913871
26 | 349.9452011 | 359.9395371 | 369.8908548
27 | 338.1432261 | 347.9502029 | 357.7197732
28 | 326.7557813 | 336.3737597 | 345.9668118
29 | 315.7666703 | 325.2012277 | 334.6164426
30 | 305.1694416 | 314.4195099 | 323.6592884
31 | 294.9747625 | 304.0429113 | 313.1063265
任何帮助都将不胜感激。
答案 0 :(得分：0)
我在思考：使用二进制搜索来遍历声明范围的结构数组：
struct Range {
float low;
float center;
float high;
int temperature;
};
struct RangeTable {
struct Range* list;
size_t length;
}
// TODO: Read the file here
struct RangeTable* table = ...
// NOTE: Ensure table.list is sorted in ascending `center` value, either in the file, or use a sorting function on the array after loading.
/////////////
/// <summary>Looks up the <paramref="adcReading" /> value in the provided table and returns a pointer to the best-matching Range struct value.</summary>
struct Range* lookup( struct RangeTable * table, float adcReading ) {
// do a binary-search on the `center` value, which will return the Range object with the closest `center` value.
struct Range* closestCenter = binarySearch( table->list, table->length, adcReading );
if( closestCenter == NULL ) {
// error condition.
exit( 1 );
}
if( adcReading < closestCenter->low || adcReading > closestCenter->high ) {
// out of range
}
else {
// inside the range
}
}
当然，实现排序和二元搜索功能取决于你。
答案 1 :(得分：0)
这是一些可行的代码。它假设映射表是内置的;如果你需要动态地阅读它，那需要一些修改后的代码，但这不是一个基本问题。
如comment中所述，代码确定每个温度的整数ADC值，这样如果该值大于极限，则温度为给定值，使用ADC中心值条目之间的线性插值在原始ADC数据表中。搜索相关温度是一种简单的线性搜索。如果需要，可以使用二进制搜索，或者为合理的ADC值创建表，并将每个ADC值映射到一个温度（使用更多空间，但提供最快的查找）。但是对于25-41ºC的范围，几乎不值得担心线性搜索的性能，除非你能证明它是一个戏剧性的瓶颈，特别是因为普通搜索只需要在开始时查看2或3个条目列表（所以正常的线性搜索可能会超出二进制搜索！）。
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
struct raw_adc
{
int temp;
double adc_lo;
double adc_mid;
double adc_hi;
};
/* Assumed sorted in order of increasing temperature */
/* Assumed monotonic in order of adc_mid values in sorted order */
/* Assumed lower temperature has higher adc_mid value */
/* Assumed ADC readings always positive (0 used as dummy) */
/* Assume contiguous series of temperatures */
static struct raw_adc raw_adc_data[] =
{
{ 25, 362.1804923, 372.3636364, 382.4913871 },
{ 26, 349.9452011, 359.9395371, 369.8908548 },
{ 27, 338.1432261, 347.9502029, 357.7197732 },
{ 28, 326.7557813, 336.3737597, 345.9668118 },
{ 29, 315.7666703, 325.2012277, 334.6164426 },
{ 30, 305.1694416, 314.4195099, 323.6592884 },
{ 31, 294.9747625, 304.0429113, 313.1063265 },
};
enum { NUM_RAW_ADC = sizeof(raw_adc_data) / sizeof(raw_adc_data[0]) };
struct map_adc
{
int temp;
int adc_value;
};
static struct map_adc adc_map[NUM_RAW_ADC];
static void map_raw_adc_values(void)
{
int i;
for (i = 0; i < NUM_RAW_ADC - 1; i++)
{
adc_map[i].temp = raw_adc_data[i].temp;
/* Optionally add 0.5 before assigning */
adc_map[i].adc_value = (raw_adc_data[i].adc_mid + raw_adc_data[i+1].adc_mid) / 2;
}
/* Last value is deemed to be hotter than the last recorded value */
adc_map[i].temp = adc_map[i-1].temp + 1;
adc_map[i].adc_value = 0;
}
static int temp_from_adc(int adc_value)
{
int i;
for (i = 0; i < NUM_RAW_ADC; i++)
{
/* Use of > determined by inspection of data - colder temps have higher ADC value */
if (adc_value > adc_map[i].adc_value)
return adc_map[i].temp;
}
assert(0); /* Can't happen! */
return 300; /* If it gets here, the machine is too hot! */
}
static void dump_adc_map(void)
{
for (int i = 0; i < NUM_RAW_ADC; i++)
{
assert(raw_adc_data[i].temp == adc_map[i].temp);
printf("T = %.3dºC ADC = (%6.2f:%6.2f:%6.2f) Limit = %d\n",
raw_adc_data[i].temp, raw_adc_data[i].adc_lo,
raw_adc_data[i].adc_mid, raw_adc_data[i].adc_hi,
adc_map[i].adc_value);
}
}
int main(void)
{
map_raw_adc_values();
dump_adc_map();
srand(time(0));
for (int i = 0; i < 20; i++)
{
/* Range of ADC values in table is 294-382 */
/* Generate random value in that range */
int adc_rdg = rand() % (382 - 294) + 294;
printf("ADC: %d = %d ºC\n", adc_rdg, temp_from_adc(adc_rdg));
}
return 0;
}
示例运行：
T = 025ºC ADC = (362.18:372.36:382.49) Limit = 366
T = 026ºC ADC = (349.95:359.94:369.89) Limit = 353
T = 027ºC ADC = (338.14:347.95:357.72) Limit = 342
T = 028ºC ADC = (326.76:336.37:345.97) Limit = 330
T = 029ºC ADC = (315.77:325.20:334.62) Limit = 319
T = 030ºC ADC = (305.17:314.42:323.66) Limit = 309
T = 031ºC ADC = (294.97:304.04:313.11) Limit = 0
ADC: 298 = 31 ºC
ADC: 358 = 26 ºC
ADC: 343 = 27 ºC
ADC: 315 = 30 ºC
ADC: 358 = 26 ºC
ADC: 352 = 27 ºC
ADC: 374 = 25 ºC
ADC: 322 = 29 ºC
ADC: 372 = 25 ºC
ADC: 376 = 25 ºC
ADC: 333 = 28 ºC
ADC: 334 = 28 ºC
ADC: 356 = 26 ºC
ADC: 307 = 31 ºC
ADC: 304 = 31 ºC
ADC: 305 = 31 ºC
ADC: 324 = 29 ºC
ADC: 358 = 26 ºC
ADC: 324 = 29 ºC
ADC: 322 = 29 ºC