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...

John ZS6WL


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?

John ZS6WL


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

Then you can 'probe' the Pi...

sudo modprobe w1-gpio
sudo modprobe w1-therm

To check this has 'worked':-
cd /sys/bus/w1/devices/
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.