need .py code for reading Max31855 A/D temp converter

for Michael Conners

Below is the error code I got running the original code from Tackie before any changes

Same error code when I tried changing to cs_pins = [8] and using other pinout's same as I started with

Same error code when I tried changing to cs_pins = 24 then clk_pin = 23,and data pin 21, I moved jumpers to corresponding gp header numbers

When I tried to run the two sudo statements from IDLE 2, I got the last to two statements below

Is running in the root supposed to give access to /dev/mem ?

>>> ================================ RESTART ================================

>>>

Traceback (most recent call last):

  File "/home/pi/max31855.py", line 175, in <module>

   thermocouples.append(MAX31855(cs_pin, clock_pin, data_pin, units))

File "/home/pi/max31855.py", line 36, in __init__

   GPIO.setup(self.cs_pin, GPIO.OUT)
RuntimeError: No access to /dev/mem.  Try running as root!

>>> sudo python max31855.py

SyntaxError: invalid syntax

>>> sudo max31855.py

SyntaxError: invalid syntax
>>>

I am more confused than ever now!

I tried using the triple quotes to comment out the last 18 lines. I didn't get any error codes but no data out either.

If I may I want to put a few more questions to you!

1.If I change the pin #'s in the code close to end of the listing just above where I used the triple quotes is that actually changing where the code above it

       is supposed to read thermocouple values and do the chip select.

2. Is there a way to get all the code lines numbered for easier troubleshooting when error is detected in IDLE?

ONE more question for now:

In the Tuckie code the last line number in his code is 170 but the error codes generated by the python shell is calling for line 175 and that is not even the end of the code.

His is counting blank lines. How is that happening?

Sorry for all the time I take from you but you have helped me a great deal to understand the code.

for Michael Conners

Below is the error code I got running the original code from Tackie before any changes

Same error code when I tried changing to cs_pins = [8] and using other pinout's same as I started with

Same error code when I tried changing to cs_pins = 24 then clk_pin = 23,and data pin 21, I moved jumpers to corresponding gp header numbers

When I tried to run the two sudo statements from IDLE 2, I got the last to two statements below

Is running in the root supposed to give access to /dev/mem ?

>>> ================================ RESTART ================================

>>>

Traceback (most recent call last):

  File "/home/pi/max31855.py", line 175, in <module>

   thermocouples.append(MAX31855(cs_pin, clock_pin, data_pin, units))

File "/home/pi/max31855.py", line 36, in __init__

   GPIO.setup(self.cs_pin, GPIO.OUT)
RuntimeError: No access to /dev/mem.  Try running as root!

>>> sudo python max31855.py

SyntaxError: invalid syntax

>>> sudo max31855.py

SyntaxError: invalid syntax
>>>

I am more confused than ever now!

I tried using the triple quotes to comment out the last 18 lines. I didn't get any error codes but no data out either.

If I may I want to put a few more questions to you!

1.If I change the pin #'s in the code close to end of the listing just above where I used the triple quotes is that actually changing where the code above it

       is supposed to read thermocouple values and do the chip select.

2. Is there a way to get all the code lines numbered for easier troubleshooting when error is detected in IDLE?

ONE more question for now:

In the Tuckie code the last line number in his code is 170 but the error codes generated by the python shell is calling for line 175 and that is not even the end of the code.

His is counting blank lines. How is that happening?

Sorry for all the time I take from you but you have helped me a great deal to understand the code.

Hi Don,

As I said, I don't have that device, I also don't use idle, but here is what I did do,

I downloaded that file, the raw file from https://raw.github.com/Tuckie/max31855/master/max31855.py

i edited the file and replaced

  cs_pins = [4, 17, 18, 24]  with cs_pins = [8]
clock_pin = 23 with clock_pin = 11
data_pin = 22 with data_pin = 9

I then did

chmod 755 max31855.py

then

sudo ./max31855.py

chmod 755 changes the permissions of the file to read, write, execute by the owner, read, execute to everyone else, it's octal

the other thing that I did, was the spi setup had me edit the /etc/modprobe.d/raspi-blacklist.conf file, i restored that to the original by uncommenting the line about spi, if you didn't do this, don't worry about it.

This program executed perfectly for me with the changes I mentioned, even though I didin't have the device, it just read 0 all the time

Python is an odd language in that spacing and file formatting is important, deviate and you will get syntax errors

my advice is to redownload the file and make only the changes I suggested, you may have to play with the pin numbers.

The last 18 lines of the file are the 'main' routine, commenting those out will do nothing but cause you problems.

Good luck,

Mike

BTW, a # will comment out a single line of python

Mike

Another thing I failed to address, unix uses access permissions for everything, like I mentioned with the chmod 755 earlier.

/dev/mem has restricted access to normal users, running as root will allow you read write access to /dev/mem, running as root, or executing a file with sudo, will elevate your user to allow access to /dev/mem, which allows you to write to the system memory map to allow access to the gpio controller.

There are ways to change this behavior, but they are more advanced unix system administration functions. Let's get your device working, then you can worry about becoming a l33t sys admin.

Mike

Thanks again for all your time. I will try your suggestions and hope for the same results.

Don

when I run this line (chmod 755 max31855.py)  on LX terminal I get:

bash: cmod: command not found

When I run this line on IDLE (python shell) I get:

SyntaxError: invalid syntax

How should I execute this commands?

Thanks again Don

when I run this line (chmod 755 max31855.py)  on LX terminal I get:

bash: cmod: command not found

 

When I run this line on IDLE (python shell) I get:

SyntaxError: invalid syntax

 

         

These should be run from a shell prompt

The first error says cmod: command not found

it should be chmod, make sure you typed it in properly,

the second error is because you are trying to run shell commands in the python console.

Mike

Oh, and yes, LXTerminal is the proper window to enter these commands.

Mike

I made a typo when I ran the command the last time to get the result to type to you.

What actually happens is in the LX terminal, typing in the command  chmod 755 max31855.py

I get no action at all just a pi@raspberrypi prompt back so I type in sudo ./max31855.py I get:

  sudo: unable to execute ./max31855.py: No such file or directory

I am thinking the name should be the same with just the attributes changed, is this correct?

Am I missing a file on the SD card?

What should the file look like in the directory? I can't find any info in my doc's that tell me what ./ means!

Don

If you have a bunch of commands you do often, you can put them together in a socalled batch file. Or we call it "shell script" in the Unix-world.

so you can create a file with:

echo The time is

date

in it. But the system likes to know what "interpreter" to use for this script. (there are multiple).  So in this case you add:

#!/bin/sh
 

as the first line and it uses the shell "/bin/sh".

Now if you store this as test1, and then chmod 755 test1, you can execute this small program with "./test1".

If, however you type: ./test2, you'll get "no such file or directory" as the error message.
The confusing thing is: if the first line is wrong, you'll get the same error message. So in my example, if the first line would have been:

#!/bin/sh2

the error message will also be: "./test1: no such file or directory"

So... with that error message, you should take a gooooood look at the first line of your max31855 script!

 

What actually happens is in the LX terminal, typing in the command  chmod 755 max31855.py

I get no action at all just a pi@raspberrypi prompt back so I type in sudo ./max31855.py I get:

 

That is normal, that means the command executed without error, in *nix, no news is often good news

if you were to do

ls -al max31855.py

you should see something like

-rwxr-xr-x 1 pi pi 6171 Feb 14 20:13 max31855.py

in the output, that means you have set the (r)ead,(w)rite,and e(x)ecute bits for the owner

this is good

the prefix ./ simply means, in the current directory (./) find the file, and in this case execute it,

so

sudo ./max31855.py

means execute max31855.py as the super user

now the first line of that file, if you did as I said and downloaded it again, will have

#!/usr/bin/python

that means, use /usr/bin/python  to interpret the following commands contained in the file.

if you type

which python

at the command line, you should be treated to the output

/usr/bin/python

if it does not print that, then your python interpreter is installed in another location, and that should be the first line of your program.

I'm realizing that you are very new to all of this, but it's ok, that is what we are here for.

Good luck,

Mike

PS. I can't wait for you to get this to work.