[sdiy] LFSR digital noise source

rsdio at audiobanshee.com rsdio at audiobanshee.com
Tue Nov 12 00:01:20 CET 2019

On Nov 11, 2019, at 1:35 PM, Gordonjcp <gordonjcp at gjcp.net> wrote:
> On Sun, Nov 10, 2019 at 02:19:32PM -0500, bbob wrote:
>> yes, hardware is what i seek
> The best way to do it in hardware is actually to just implement an LFSR
> in a small microcontroller.

The real problem here is all of the overhead required to get it working. A microcontroller doesn’t do anything when you first solder it to a board, or plug it into a breadboard. So, you have to buy a programmer and attach it to your prototype. Even then, you’re not done. You have to write the code, test the code, and iterate. Finally, even after you’ve finished getting all of the software bugs out, the non-volatile memory can forget your program, and you might be back to square one.

There are certainly problems that can’t be solved without a microcontroller. That’s why we have them. But they’re not always a win compared to logic circuits that perform the correct function as soon as power is first applied, without the need for additional tools, circuit adaptors, and software development. The most expensive part of any product design is the software. If you can design something without software, you’ve saved yourself the biggest cost. Whether you’re considering a one-off project or a product that you want to manufacture, there are many functions that are best done in hardware, without software.

> It's incredibly tweakable, without having to find long-obsolete parts
> that were profoundly shitty when new and are unlikely to have been
> improved by lying around for 30 years.

There’s no reason to design with obsolete parts that have been sitting around. There are plenty of modern, in-production logic chips. They are also available in a variety of performance levels, from the slowest TTL to much faster. Many of these chips operate at 40 V peak-to-peak, which an MCU can’t possibly handle without external help.


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