This project is a simple waveform generation using the MCP4802 DAC on the Raspberry Pi.
Wire up the breadboard as shown below.
The output of the DAC is on pin 8 (channel 0). The example software is a triangle waveform.
To install the software:
wget http://skpang.co.uk/dl/mcp4802.tar
Unpack the tar file and change into directory by:
tar xf mcp4802.tar
cd mcp4802
Compile the software by:
make all
Start the example by:
sudo ./dtoa
Using an oscilloscope the output waveform can be viewed. The main routine is in dtoa.c file
To stop the program running press CTL-C
We are struggling to get an analog output from our Pi. We are using a MCP4921, which differs from yours in that it is 12 bit and it uses an external V_Ref. While attempting to use your method, I’ve come to receive seemingly nothing at the output of the DAC. I have it connected just as yours with the exception of the V_Ref pin. I’ve changed a couple lines of code (gb_spi.c 106 and 112 by adding one F to the equation to accommodate one additional byte.) The four most significant bits should be the same on our chips. I am receiving some square signals at the MOSI, clock and CS pins, which seem reasonable. Do you have any thoughts as to where the issue lies?
-Shane