I’d heard that pifm, the raspberry pi radio pin thing used 1-bit quantization techniques. I was wondering what they were.
The basic idea of no free lunch states that you can trade the very high speed excess of a fast digital circuit for more effective bit depth of reconstruction.
A natural technique is pulse width modulation, but then you need an integration stage. Low pass filtering elements are more common. Sigma-Delta conversion is a technique that pushes quantization noise into higher frequencies such that a low pass filter will reconstruct the signal well. Pins natural have capacitance so you might get a low pass filter with no external circuitry at all if you’re going really ghetto.
I did some things with dithering and Sigma-delta in python. Interesting.
The seller of the Cyclone IV RZ-EasyFPGA A2.1 had the following pinout on the page. I paid about 35$ and it took maybe 3 weeks to get here from china.
It came with a usb blaster programmer. and some usb cables. It can be powered from usb or from a 5 volt supply. I also got a camera.
This is better than the cyclone II chip I had before. More logic units, and I can use the newest version of Quartus II 16.1. I like having some accessories on board
So I have a couple boards now.
Make a new project. Select Cyclone IV E series. EP4CE6E22C8 is the right chip. EP4CE6E22C8N is what the seller says. What does the N mean?
Here is a very simple counter. The clk is 50Mhz clock so I attached bits 25 to the leds in the pin assignment. That should be slow enough for me to see.
make a new verilog file with the same name as the project. This is the top level design file
module blinkcyclone4 (
out , // Output of the counter
clk , // clock Input
output [25:0] out;
reg [25:0] out;
//-------------Code Starts Here-------
always @(posedge clk)
out <= out + 1;
In the programmer window select the .sof file in the output folder .
Now let’s try getting those LED digits up
The Dig signal needs to be clocked? It probably accepts on a positive edge or something. No. The dig signal is active low. I probably need to have the thing cycle through really fast. There is probably no memory in the led unit