Category Archives: Raspberry Pi

Getting started with Pine64

Raspberry Pi – getting the RFM12b to work

Now that I know how to blink a LED, it is time to move to slightly more interesting applications of the GPIO interface on the Raspberry Pi. I have a few Arduino modules in and around the house monitoring the climate and various other measures. They are all battery operated and send their information to a relay that forwards all data to Thingsspeak.

My current relay module consists of an Arduino Uno with an Ethershield, connected over i2c to another Arduino pro mini. The second Arduino is connected to a RFM12b module and uses JeeLib to receive data from the sensing modules. Would it not be nice to receive that data on a slightly more powerful platform and be able to do more with it than just forwarding it elsewhere…

Raspberry Pi with RFM12b

I decided to give the rfm12b-linux kernel driver a try, as it explicitly supports the JeeLib format. I followed the instructions from rbi-source without problems. After changing the board type (RFM12B_BOARD) and group (RFM12B_DEFAULT_GROUP_ID) in rfm12b_config.h, the module compiled without problems. However, it would initially not load, showing errors in the dmesg output.

Following some suggestions here and here, I used rasps-config to disable the SPI, I2C and the Device Tree. After that, it did load and dmesg showed

[ 478.278166] rfm12b: added RFM12(B) transceiver rfm12b.0.1 [ 478.278391] rfm12b : driver loaded.

I compiled the example applications and used this

pi@hackpi:~/rfm12b-linux/examples/bin $ sudo ./rfm12b_read 

successfully opened /dev/rfm12b.0.1 as fd 3, entering read loop...

Fri Apr 29 20:07:50 2016
	32 bytes read
		4 0 0 0 115 24 0 0 87 14 109 64 102 230 11 65 41 44 124 68 
		0 0 192 127 0 0 192 127 115 162 189 253 
Fri Apr 29 20:08:14 2016
	32 bytes read
		2 0 0 0 59 77 2 0 122 233 110 64 210 225 148 65 0 0 192 127
		0 0 192 127 0 0 192 127 93 112 175 32

showing two messages from two modules. I recognise the pattern as

typedef struct payload_t {
  unsigned long id;
  unsigned long counter;
  float value1;
  float value2;
  float value3;
  float value4;
  float value5;
  unsigned long crc;
};

belonging to the lm35 and bpm085 modules that are sending their data approximately every minute.

Raspberry Pi – first steps to blink a LED with Python

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I already purchased my first Raspberry Pi in 2011, but have been postponing connecting any electronics to its GPIO interface. Instead, I have been using it for more general computing applications (media center, web server, remote ssh access and tunnel, etc.). Rather than using the Raspberry Pi for in refacing with hardware and IOT, I have been using a bunch of Arduino’s to implement sensors and actuators for home automation.

Since I recently have been brushing off my Python programming skills for the EEGsynth project and been teaching myself Node JS, I was triggered to revisit the Raspberry Pi for GPIO electronics. With the Raspberry Pi it will be easier to implement my own web server and to use webhooks to integrate my home automation hardware projects with online platforms such as IFTTT.

I decided to try Python first and after browsing the web decided to use the WiringPi interface, as it supports C programming in the same style as on the Arduino, but also has wrappers for more high-level languages (Python, PHP, Ruby and Perl).

I started with installing the WiringPi library as per instructions

git clone git://git.drogon.net/wiringPi
cd wiringPi/
./build

and tested it with a LED in series with a 680 Ohm resistor attached to the first GPIO pin, aka pin 17 on the Pi cobbler. I still have to wrap my head around the pin numbering, but understand that there are different numbering schemes.

Subsequently I ran the test from

cd examples/
make blink
sudo ./blink

and also tried out this on the Linux command line

gpio write 0 1
gpio write 0 0
gpio write 0 1
gpio write 0 0

This all worked as expected and the LED would nicely blink. I subsequently moved on with Python. Instead of following the detailed installation instructions, I simply tried

sudo pip install wiringpi

which worked like a charm. The following Python code

#### this is blink1.py #### 

import wiringpi
import time

wiringpi.wiringPiSetup()

wiringpi.pinMode(0,1)

while True:
    time.sleep(0.5)
    wiringpi.digitalWrite(0,1)
    time.sleep(0.5)
    wiringpi.digitalWrite(0,0)

works with sudo, i.e.

sudo python blink1.py

As with the pin numbering, it is still a bit of a puzzle to me when super user rights are needed and when not. But the following worked for me without sudo

#### this is blink2.py #### 

import wiringpi
import time
import os

wiringpi.wiringPiSetupSys()

os.system('gpio export 17 out')

wiringpi.pinMode(17,1)

while True:
    time.sleep(0.5)
    wiringpi.digitalWrite(17,1)
    time.sleep(0.5)
    wiringpi.digitalWrite(17,0)

and then on the Linux command line

python blink2.py

It is already rewarding to see a simple LED blink. Next challenges will include combining it with a RFM12B or RFM69CW module to have the Rasperry Pi receive the messages from the (battery operated) Arduino’s for which I use the RFM12B for communication.

Furthermore, Adafruit has a nice tutorial showing how to use Node JS with a Raspberry Pi. That is also something to explore…

Raspberry Pi as Eurorack synthesizer module

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Processing realtime EEG data from the OpenBCI system requires software running on a computer. For the EEGSynth project we do the rapid application development using the platforms that we are most familiar with, i.e. standard laptops and the FieldTrip toolbox, which is based on MATLAB. However, in the end we want to implement as much as possible using affordable and open hardware and software. Hence we opted for the Raspberry Pi, a credit card–sized single-board computer. It runs Linux, which makes it easy to use standard programming platforms and interfaces such as Python and Redis to implement the software stack.

In the first EEGSynth studio performance you can see Stephen in the middle, operating the MATLAB-based GUI for the EMG/EEG processing, and Jean-Louis at the back operating the synthesizer. The goal of the technological development is to put Jean-Louis completely in control and to make the interface of the EEG synthesizer as similar as his other modular synthesizer modules. Hence the need for fitting the Raspberry Pi into a Eurorack synthesizer case.

Here you can see some photo’s from the construction of the front panel.

The front plate has holes for the various interface ports to interface with the Raspberry Pi. For a sturdy mount I glued a section of L-profile rails to the front plate.

After mounting the Raspberry Pi, I connected the HDMI and audio port with a short cable to the front panel.

Here you can see the Raspberry Pi in the Eurorack case, next to the power supply.

Robert Oostenveld’s blog

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Category Archives: Raspberry Pi

Getting started with Pine64

Raspberry Pi – getting the RFM12b to work

Raspberry Pi – first steps to blink a LED with Python

Raspberry Pi as Eurorack synthesizer module

Raspberry Pi arrived