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.

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

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