I'm F4HDK, the creator of these NPR modem. The unprotected telnet access is only for local management, especially when you connect only 1 PC to one NPR Client modem. If you need security for accessing configuration/management features of the modem, then you can deactivate the telnet server inside the modem, and put a R-Pi dedicated for that feature, which will be plugged locally to the modem via USB. Then you access the R-Pi via SSH. This is explained in the "advanced user guide". But of course trafic will be kept unecrypted, due to amateur-radio regulations. (telnet is only for management-configuration).

I still use wire-wrapping with veroboards quite often for my home hobby. I like this method, because above certain frequency, it is fairly difficult (quite impossible) to use Breadboards because of electromagnetic issues. The goal is to test different configurations, to rapidly test a new component, explore new ideas quickly. On Veroboard, the wire-wrapping method enables very dense connections.

Maybe I have not understood in details what you mean... but my A2Z CPU has no internal (hardware) stack pointer, unlike the 8051. The only available addressing mode is "direct addressing". Of course, you can emulate indirect addressing modes, and you can emulate 32 bits manipulations... But it will be not optimal at all (=very slow compared to programs using only direct addressing). Here, on A2Z, the compiler matches the simplicit of the CPU architecture, it is the same philosophy : only static allocation for variables. If I wanted a custom CPU compatible with a C compiler and with Linux, the CPU would have been totally different.

Thank you very much for this encouraging comment! I ended my studies 15 years ago, I made this project as an "autodidact". I don't know if I will work again on such projects, because I have tons of other electronic topics I want to work on (mainly radio). But if I pick it up again, it will be with a brand new CPU project.

Why do you compare my A2Z project with RISC-V? Have you read the pages and the blog posts on hackaday? Have you understood what A2Z is? A2Z is (only) a DIDACTIC project. The goal is learning by doing, and therefore the goal is to reinvent the wheel, just for fun. The "learning by doing" method is the best method I know. The principle is absolutely NOT to take an existing CPU or OS and assembling existing parts. And of course, I have learned a lot of things with this method. That's why I'm sharing this project. I hope some people will begin such project on their own, and learn as much as I did.

You are right, but my A2Z is not like old cars or vintage computer. It's more like designing and building from only few existing parts a karting, or a small buggie, without refering to existing drawings. A very simple machine, not very advanced, but that I understand in all its details.

It's like a form of art, and this is great artistry. Thanks/merci for sharing, it's motivational to see these things reach a "finished" state.

Yes, the "finished" status of A2Z is what I am the most proud of. Lots of "CPU on FPGA" projects only deal with the CPU itself, and will never become a fully "usable" computer. I managed to work on the 3 main topics : hardware, software dev toolchain, and software itself.

It really depends on you current skills. If you already know about electronics, and roughly what an FPGA is, and if you know C programming, then you can jump rapidly to FPGA and Verilog. One good and very condensed training course below: http://www.ee.ic.ac.uk/pcheung/teaching/ee2_digital/Altera%2...

You are 100% right. This project fits 100% with my personality. I like to understand in details what I'm working on, even if I need to "loose" time exploring things not directly linked to what I'm supposed to do. And I also like systems that are designed at necessary level.

Hi, this is fantastic! Thanks for sharing.

I would be curious to know what your level of proficiency was in some of these areas such as C, Verilog, writing assemblers, programming FPGAs, board wrapping, etc.

How much learning did you as you went vs how much prior exposure did you have to some of these things?

Are there any resources you found helpful or that you would recommend to others who want to undertake a similar project?

Cheers.

I started this project with only standard electronic knowledges. I had no experience of FPGAs, of writing compiler and assemblers. I learned these topics as an autodidact. It is a "learning by doing" project. And of course, I have learned tons of new things, this is a very rewarding project.

The source code is compatible with Altera Quartus II. You can also execute the A2Z emulator on your PC, without the Altera suite.

How long did it take you to do this? Did you have previous experience with all the various aspects (compiler, FPGA, instruction set etc) before or did you build it up as you went along?

I am an autodidact for all these things (FPGA, compiler). This is my first FPGA-Verilog project and my first compiler project. I have learned these things specifically for this project. It took me 2 years to complete this project, during evenigs and week-ends. I have not counted exactly, but probably between 200 and 400 hours of work.