2015-07-31

Ham-Comp / Raspberry Pi Session 7

Tomorrow is the postponed meeting at the Club House for Raspberry Pi and Ham-Comp. I say both because the Pi' is starting to get used for 'other' things...

I am going to be there from 13:00 to 17:00 with a short presentation on Peripherals and SPI/I2C. 

This all assumes I can defrost in time...

73
John ZS6WL
 


2015-07-24

So tomorrow is SCOPEX not Raspberry Pi

So you have to wait another week for the Raspberry Pi session. Any thoughts on what we might cover?
  • Maybe the use of an LCD panel with the Pi?
  • Maybe a temperature monitor 'app' ?
  • With a web server page that can be accessed from the Internet? [Oh sorry that's been done...maybe that is a project in itself?]

Hardware - I found an HDMI to DVI connector adapter at the China Mall. I also found that I could install REAL ENGLISH Dictionary into Firefox. So the spell checker in this blog does not consider me a Canadian!

Nico phoned me this week with an application for the Pi that measures pressure in a pipe. Unfortunately the sensor is an analogue sensor. So I went looking for an A2D chip that can do the job... maybe that is another subject for Saturday week?

73
John ZS6WL

2015-07-02

Raspberry Pi - Getting the temperature sensor to work.

I had 'issues' with getting the temperature sensor to work with the Raspberry Pi. So I did some more searching...

Add the following line to /boot/config.txt
dtoverlay=w1-gpio

Then you can 'probe' the Pi...


sudo modprobe w1-gpio
sudo modprobe w1-therm

To check this has 'worked':-
 
cd /sys/bus/w1/devices/
ls
 
This should show the temperature file:-
10-00080254a833 [ or similar file name][IF it doesn't, you need to check everything.]

Change directory to it:-

cd 10-00080254a833
 
To 'read' the DS18x20 [mine is so old...]
cat w1_slave

This should show something like this :-

pi@raspberrypi /sys/bus/w1/devices $ cd 10-00080254a833
pi@raspberrypi /sys/bus/w1/devices/10-00080254a833 $ cat w1_slave
23 00 5d 58 ff ff 04 10 3d : crc=3d YES
23 00 5d 58 ff ff 04 10 3d t=17500
pi@raspberrypi /sys/bus/w1/devices/10-00080254a833 $

Yes! It really was 17.5C in the study. Cool now to find a C program to get the reading...

Brad's Raspberry Pi Blog - has the answer. 

But only one 'gotcha'! The temperature sensor in current day use is a DS18B20 and mine is a DS1820. The 'output' is not '28-' but a '10-'. This requires a small change to the C program. A recompile later and all is well. Reading the sensor to three decimal places. Hmm.