berndporr/rpi_ad7705_daq

Test/demo program for using the AD7705 with the Raspberry Pi and demo how to display data on a website with FastCGI.

Data acquisition with the AD7705 on the raspberry PI!

The AD7705 is a two channel sigma delta converter which has differential inputs, a PGA and programmable data rates. It's perfect for slowly changing inputs such as pressure, temperature, heart rate etc.

This repo offers the class AD7705Comm which does all the low level communications with the AD7705. The user just need to register a callback handler which then returns the samples in realtime.

The class uses the DRDY of the AD7705 connected to Port 22 and waits for a falling edge on this port to read the data. This is done via interrupts / poll so that the ADC process sleeps until new data becomes available.

Hardware design

The design files (for EAGLE) are in the subdirectory "pcb".

Building:

To build:

cmake .

make

Install

sudo make install

Usage example

In the subdir example is a simple application which prints the ADC data to the screen.

cd example
sudo ./ad7705_printer

General usage

The online doc is here: http://berndporr.github.io/rpi_AD7705_daq/

Callback handler

class AD7705printSampleCallback : public AD7705callback {
	virtual void hasSample(float v) {
		// process your sample here
	}
};

Main program

Instantiate the AD7705 class and the callback handler:

	AD7705Comm ad7705comm;
	AD7705printSampleCallback ad7705printSampleCallback;
	ad7705comm.setCallback(&ad7705printSampleCallback);

Start the data acquisition:

	ad7705comm.start();

once start has been called the data will be arriving.

Stop the data acquisition:

	ad7705comm.stop();

Author: Bernd Porr

• [email protected]
• [email protected]
• www.berndporr.me.uk