Re: [lwip-devel] Porting advice for 8 bit OS OS-9

[address@hidden]

Am 22.01.2021 um 01:39 schrieb Walter ZAMBOTTI:
> Hi all,
>
> I'm considering using lwIP in a 8 bit RTOS called OS-9 (by Microware). 
> I'm using the original 8 bit version which came without a network stack.
>
> I have some constraints!!!
>
> 1. Memory limitation
>
> The kernel only has 64k for program and data.  A memory management unit
> allows for greater than 64k memory usage but each task and the kernel
> are limited to 64k. So the kernel and tasks run in their own 64k space.

64k for program and data are quite limited for lwIP. I don't know which
protocols you want to run, but I don't think this will suffice for lwIP.
It will get tough at least.

Typically, you'll want to look for something smaller than lwIP here
(e.g. uIP/contiki, but I don't know how well this is supported nowadays).

>
> Looking at memory constraints I want to know what options will give me
> the smallest footprint.

Look through opt.h and create your own lwipopts.h that turns
*everything* off that you don't need (or don't know if you need it).
Then, compile it and see how much memory for data you have left...

>
> Is it possible to configure the use of just IP4 without IP6 (if it makes
> it smaller one will suffice).
>
> 2. Multi threaded or not
>
> The RTOS is multitasking but not multi-threading so it does respond to
> interrupts and multiple tasks run concurrently.
>
> Looking at the porting guide I'm not sure if I should chose the threaded
> option or not!

No, chose the non-threading style (but I say so because of memory
constraints).

>
> 3. Timer/Interrupt resolution
>
> The interrupt resolution is 16 milliseconds (tied to the screen vertical
> interrupt) but i may be able to leverage the horizontal screen
> interrupts for finer resolution.
>
> Will this pose a problem?

I don't think so.

>
> ---
>
> Bottom line.  Do you think I can achieve this on such an architecture?

As I said above, I'm not sure you can. You'd have to try.

Regards,
Simon