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Rasperry Pi turi 1-wire protokolo palaikymą. Pats populiariausias W1 įrenginys yra skaitmeninis termometras DS18B20

panaudojus sita gida pavyko gauti temperaturas ir jas irasyti i faila: http://www.cl.cam.ac.uk/projects/raspberrypi/tutorials/temperature/

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
 
/*
gcc -Wall -pthread -o w1_temp_rec w1_temp_rec.c && sudo ./w1_temp_rec
sudo ./w1_temp_rec
 
watch -n10 ./w1_temp_rec
*/
 
int main()
{
    FILE * temp_log = fopen("temp_log.txt", "a");
 
    time_t now;
    time(&now);
    char buf[sizeof "2011-10-08T07:07:09Z"];
    strftime(buf, sizeof buf, "%FT%TZ", gmtime(&now));
    //printf("%s\n", buf);
 
    printf("record temperature readings to file\n");
    FILE * fp;
    char * line = NULL;
    size_t len = 0;
    fp = fopen("/sys/bus/w1/devices/28-031688217aff/w1_slave", "r");
    getline(&line, &len, fp); //printf("%s", line);
    getline(&line, &len, fp); 
    strftime(buf, sizeof buf, "%FT%TZ", gmtime(&now)); 
    printf("%s OUT %s", buf, line);
    fprintf(temp_log, "%s OUT %s", buf, line);
 
    fclose(fp);
 
    fp = fopen("/sys/bus/w1/devices/28-03168812d2ff/w1_slave", "r");
    getline(&line, &len, fp); //printf("%s", line);
    getline(&line, &len, fp); 
    strftime(buf, sizeof buf, "%FT%TZ", gmtime(&now)); 
    printf("%s IN %s", buf, line);
    fprintf(temp_log, "%s IN %s", buf, line);
    fclose(fp);
 
    fclose(temp_log);
 
 
    if (line) free(line);
    return 0;
}

Paleidau 2 termometrus, viesnas matuoja temperatūrą namuose kitas lauke. Tada nubraižiau grafikus su matlab ir gavau toki vaizdą:

%% read temerature log and plot chart
fileID = fopen('\\aistis\pihome\home\pi\temp_log.txt','r');
C = textscan(fileID,'%s %s %s %s %s %s %s %s %s %s %s %s');
fclose(fileID);
disp(C);
clear d
for i=1:length(C{1})
  d(i).date = datenum(C{1}{i},'yyyy-mm-ddTHH:MM:SSZ');
  d(i).type = C{2}{i};
  z = strsplit(C{end}{i},'=');
  d(i).temp = str2num(z{2})/1000;
end
 
figure(1);clf;
l = strcmp({d.type},'IN');
plot([d(l).date],[d(l).temp]);
dynamicDateTicks;grid on;title('temperature in the house');
xlabel('time');ylabel('temperature in celcius');
 
figure(2);clf;
l = strcmp({d.type},'OUT');
plot([d(l).date],[d(l).temp],'r');
dynamicDateTicks;grid on;title('temperature outside');
xlabel('time');ylabel('temperature in celcius');

Ir gavau tokį vaizdą. Čia tarpas prieš 9 tai buvo perkrautas RPI ir kurį laiką nerašė duomenų į failą.