Testing multiple DS18B20 sensor cables

Question

I'm really new to python and coding in general so i turn here for help. At work we need to test many cables with up to five DS18B20 sensors attached to them. We got this program and we've been using it for a while now to test cables with raspberry Pi. But there are few problems with it.

The program needs to detect the number of sensors attached and see if they're working, then list them by serial number lowest>highest (so we can warm them up, see which one gets highlighted, one by one and physically number them) and repeat.

It feels generally slow and crashes pretty often. With the cables that have 5 sensors attached to them, it can find the sensors on max 2 cables(more if lucky), and when you attach 3rd cable it won't find them anymore or it will keep saying that there's 10 sensors attached. Rebooting the Pi fixes it but it takes time. Hot-swapping the cables is probably the main culprit here, but its the fastest way.

With 3 sensor cables you can check 4-5 of them until it hangs.

Any hints where the problem could be or how i could make things more efficient and faster are welcome.

Code:

import os,sys,time
import curses
stdscr = curses.initscr()

begin_x = 5; begin_y = 5
height = 40; width = 40  

def temp_raw(sensor_str):
    f = open(sensor_str, 'r')
    lines = f.readlines()
    f.close()
    return lines

def read_temp(sensor_str):
    lines = temp_raw(sensor_str)
    while lines[0].strip()[-3:] != 'YES':
        lines = temp_raw(sensor_str)
    temp_output = lines[1].find('t')
    if temp_output != -1:
        temp_string = lines[1].strip()[temp_output+2:]
        temp_c = float(temp_string) / 1000.0
        return temp_c
init = 1
timer = 0
search = 1
curses.noecho()
curses.curs_set(0)
subdirectories = []
old_nbr_of_subdirs = 1
nbr_of_subdirs = 1
old_subdirectories = []
os.system('modprobe w1-gpio')
os.system('modprobe w1-therm')

while (1):
    timer = timer + 1

    while search == 1:
        stdscr.addstr(10,30, "Searching for sensors");
        subdirectories = os.listdir("/sys/bus/w1/devices/");
        nbr_of_subdirs = len(subdirectories);
        time.sleep(3)
        if nbr_of_subdirs > old_nbr_of_subdirs:
            stdscr.addstr(10,30, "Found %d new sensors           " % (nbr_of_subdirs-old_nbr_of_subdirs));
            stdscr.addstr(11,30, "Is this all sensors? (y/n)?");
            stdscr.refresh()
            c = -1;
            while(c == -1):
                c = stdscr.getch();
                if c == ord('y'):
                    stdscr.addstr(10,30, "                                   ");
                    stdscr.addstr(11,30, "                            ");
                    stdscr.refresh()
                    old_nbr_of_subdirs = nbr_of_subdirs;
                    init = 1;
                    search = 0;
                    timer = 0;
        else:
            stdscr.addstr(10,51 + timer, ". ");
            timer = timer + 1;
            timer = timer % 4;
            stdscr.refresh()



    if init == 1:
        init = 0
        alive_ticker = 0;
        temp_list = [];
        sensor_oldtemp = [0,0,0,0,0,0];
        sensor_temp = [0,0,0,0,0,0];
        active_sensor = [0,0,0,0,0,0];
        sensors = 0;
        alive_ticker = 0;
        active = 2;
        confirm = 0; 

        stdscr.addstr(17,0, "Number of subdirectories %d" % (len(subdirectories)));
        removed = 0;
        index = 0;
        length_old_subdirs = len(old_subdirectories);
        while (index < length_old_subdirs):
            length_old_subdirs = len(old_subdirectories);

            if old_subdirectories[index] in subdirectories:
                subdirectories.remove(old_subdirectories[index]);
                removed += 1;
                index += 1;     

            else:
                old_subdirectories.remove(old_subdirectories[index]);
                index = 0;


        stdscr.addstr(30,20, "Removed %d" % (removed))


        stdscr.addstr(18,0, "Number of CUT subdirectories %d" % (len(subdirectories)));


        stdscr.addstr(19,0, "Number of  old_subdirectories %d" % (len(old_subdirectories)));

        stdscr.addstr(13,20, "Press space to confirm active sensor!");
        stdscr.addstr(14,20, "Press r to reset!");

        for index in range(len(subdirectories)):
            if subdirectories[index].find("28") != -1:
                temp_list.append("/sys/bus/w1/devices/"+subdirectories[index]+"/w1_slave");
                sensor_temp[sensors] = 0;
                sensors = sensors + 1;
                old_subdirectories = old_subdirectories + subdirectories;
                temp_list.sort();

    if confirm == 1:
        stdscr.addstr(13,20, "Press space to confirm active sensor!");
        stdscr.addstr(14,20, "Press r to restart!");


    curses.halfdelay(1);
    c = stdscr.getch();

    if c == 32:
        confirm = 0;
        timer = 10
        for z in range(sensors):
            if active_sensor[z] > active:
                stdscr.addstr(z+5,20, "                                                                      " , curses.A_DIM)
                active_sensor[z] = 100  
                stdscr.refresh()
    elif c == ord('n'):
        init = 1
        continue

    elif c == ord('r'):
        for z in range(sensors):
            active_sensor[z] = 1;

    if (timer > 9):
        timer = 0
        nbr_active_sensors = 0
        for y in range(sensors):
            if 99 > active_sensor[y]:
                nbr_active_sensors = nbr_active_sensors + 1;
                sensor_temp[y] = read_temp(temp_list[y]);
                if ((sensor_oldtemp[y] + 0.1) < sensor_temp[y]):
                    active_sensor[y] = active_sensor[y] + 1;
                    sensor_oldtemp[y] = sensor_temp[y]

        stdscr.addstr(3,5, "nbr_active_sensors=%d" % (nbr_active_sensors))
        stdscr.addstr(4,5, "sensors=%d" % (sensors))

        if nbr_active_sensors == 0:
            search = 1
            timer = 0;
            continue

        for x in range(sensors):
            if (99 > active_sensor[x] and active_sensor[x] > active):
                confirm = 1         
                stdscr.addstr(x+5,20, "Sensor %d value %4.2f ID:%s : %d " % (x+1, sensor_temp[x], temp_list[x][20:-9], active_sensor[x]), curses.A_STANDOUT)
            elif active_sensor[x] <= active:
                stdscr.addstr(x+5,20, "Sensor %d value %4.2f ID:%s : %d " % (x+1, sensor_temp[x], temp_list[x][20:-9], active_sensor[x]))
        stdscr.refresh()
        alive_ticker = alive_ticker + 1
        stdscr.addstr(2, 55, "Alive ticker: %6d" % (alive_ticker))

Answer 1

Question : when you insert the 3rd cable (with 2-3 temp sensor on them) it just won't find any new sensors anymore.

If I recall properly there is a Limit of 2 Cable. Have you verified your Hardware supports more Cable?

I suggest to rewrite the Code and separate the Code into UI, Sensor and Wire Parts.

For instance:

class DS18B20(object):
    ...
    def read(self):
        ...

class One_Wire(object):
    def search(self):
        print("Searching sensors")
        ...

    def read(self):
        print('Reading sensors')
        for key in self.sensors:
            self.sensors[key].read()

    def refresh(self):
        print("Refreshing sensors")
        ...

    def history(self, alive=True):
        print('Reading History')
        ...

Usage :

if __name__ == '__main__':
    oWire = One_Wire()

    oWire.search()
    print(oWire)

    oWire.refresh()
    print(oWire)

    oWire.read()
    print(oWire)

    history = oWire.history()
    print(history)

Output :

Searching sensors
Sensors:5, active:5
id:i2c-0 CONNECT temp:None, id:i2c-3 CONNECT temp:None, id:i2c-1 CONNECT temp:None, id:i2c-5 CONNECT temp:None, id:i2c-6 CONNECT temp:None
Refreshing sensors
NEW Sensor:i2c-2
NEW Sensor:i2c-4
Sensors:7, active:6
id:i2c-0 CONNECT temp:None, id:i2c-2 CONNECT temp:None, id:i2c-3 CONNECT temp:None, id:i2c-1 disconnect temp:None, id:i2c-5 CONNECT temp:None, id:i2c-6 CONNECT temp:None, id:i2c-4 CONNECT temp:None
Reading sensors
Reading sensors
Reading sensors
Sensors:7, active:6
id:i2c-0 CONNECT temp:19, id:i2c-2 CONNECT temp:25, id:i2c-3 CONNECT temp:26, id:i2c-1 disconnect temp:None, id:i2c-5 CONNECT temp:25, id:i2c-6 CONNECT temp:18, id:i2c-4 CONNECT temp:30
Reading History
[{'i2c-0': [20, 27, 19]}, {'i2c-2': [30, 21, 25]}, {'i2c-3': [23, 29, 26]}, {'i2c-5': [30, 18, 25]}, {'i2c-6': [30, 21, 18]}, {'i2c-4': [24, 18, 30]}]