So, compadres, this (57) being my birthday, gimme some free advice!

I got am a (noobs) model B+  Rpi.  I got an LM75.  I have them connected, the I2C device shows up properly with I2Cdetect.  My question, to which there is no 'right' answer is: What computer code should I use here?

My background is that I have been coding since 1975.  I know BASIC, Pascal, C, C++ and Prolog pretty well.  I am new to Python, but I do have experience with procedural coding from OpenSCAD.  My OS chops are on the spectrum leading to expertise, somewhere in the middle.  Mostly an apps guy.

Hi Don,

Happy Birthday!

Most online examples use Python. But if you want to use C, then there is some example I2C code here that you could check out:

https://github.com/shabaz123/lcd3

To simplify things I created a few high-level functions that are defined in i2cfunc.h.

The actual underlying control is standard linux kernel i2c driver, I just wrapped it up with a tiny bit of code to make a more friendlier (to me)

API than the standard one.

To download the code type

git clone https://github.com/shabaz123/lcd3.git

The, follow the instructions at the section titled 'Software' at this URL:

Building a Low Power Compact LCD Display

Replace the code with the code below, which is a guess for LM75 (this code isn't tested and is also missing any error handling); if there

is a permissions issue then try running as root user. If it still doesn't run, check to see that /dev/i2c-1 exists. You also may need to change the

#define address value depending on what address is hard-coded on your LM75 board.

I hope it works but it is untested. The code at github did work with an I2C LCD. And I have used the I2C library for several different I2C devices, just not the LM75 yet.

#include <stdio.h>
#include "i2cfunc.h"


// look to see if /dev/i2c-x exists
// (where x is usually 1):
#define I2CBUS 1


// LM75 address range is 0x48 to 0x4f depending on A2..0 values
#define LM75_ADDR 0x48


int handle;
unsigned char buf[2];


int
main(void)
{
  
  handle=i2c_open(I2CBUS, LM75_ADDR);

  i2c_read(handle, buf, 2);
  
  printf("temperature register values read are 0x%02x, 0x%02x\n", buf[0], buf[1]);
  
  i2c_close(handle);
  return(0);
}

There are probably other Pi-friendly libraries for GPIO and I2C, however I like using my library since it is portable and works with the BeagleBone black too, and doesn't have API names with the text 'Pi' in it.

However, most on-line code examples for the Pi will probably use Python, which is not a language I'm familiar with to any real extent.

If you're interested in using Python, the magpi PDF magazines will likely have lots of info (there is a search capability but sadly it isn't very good). https://www.raspberrypi.org/magpi/

There is some general Pi GPIO information here, although I2C is not covered; the information is about a year old though, but most of it is still relevant although it doesn't mention the Pi 3 (since this wasn't available at that time):

Raspberry Pi GPIO Explained

Happy Birthday Don, I am really glad that Shabaz jumped in there and gave you a good answer. You young guys are so quick with all this computer coding stuff. Have fun with the Rpi.

John

Happy birthday. If you prefer C to Python, wouldn't this be a suitable starting point?

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/hwmon/lm75.c

Yeah, there really is no correct answer. Python is fairly simple to learn and much of the low level stuff is abstracted out.

I've done a few blog posts here on e14 and I've alternated between C and python. There are some cool toolkits available for python, such as flask which can allow you to easily make data read from sensors available via a URL.

It's probably not a bad answer to get familiar with both C and python.

Happy birthday!!!

Mike

Hi Don,

Congratulations on your milestone.

With an RPi, python is pretty easy to learn.

You could go to Sketch, but with your experience python would be a better choice.

DAB