The ADS1115 is a sigma delta converter which has a PGA and a programmable sampling rate from 8Hz..860Hz. It's perfect for slowly changing inputs such as pressure, temperature, heart rate etc.
This repo offers the class ADS1115rpi which manages the
communication between the ADS1115 and the client who just needs to
implement the callback hasSample(float sample) which is then called
at the requested sampling rate.
The class uses the ALERT/RDY pin of the ADS1115 connected to GPIO 17 to establish the sampling rate. Without this connection this driver won't work. The ALERT/RDY pin wakes up a thread when a sample is available which then calls the callback interface with the sample value.
apt-get install cmake
apt-get install libgpiod-dev
To build:
cmake .
make
sudo make install
Data printer: In the subdir example is a simple application which prints
the ADC data to the screen or you can pipe it into a file.
cd example
./ads1115_printer
Data plotter: In the subdir rtplotter is a simple QT plotting application.
The online doc is here: https://berndporr.github.io/rpi_ads1115/
You need to register a function:
void(float);
at registerCallback(f) which then receives the voltage readings at the
requested sampling rate. If you want to call another method in another
class you can use a lamda function.
myAD7705comm.start(settings)
Once start has been called hasSample will be called at the
specified sampling rate.
You can switch to another channel inside the callback handler by
calling setChannel (ADS1115settings::Input channel) and then cycle
through the channels. You might need to let the ADC settle to the
next channel so it's recommended to read every channel twice and
then discard the 1st callback event after having switched the channel.
myAD7705comm.stop();