Re: ****tability: Harmony between PC and microcontroller

Thanks for the reply.


On May 5, 3:42=A0am, Jack Klein <jackkl...@[EMAIL PROTECTED]
> wrote:

> Try doing another embedded project, this time with an ARM. =A0ST just
> announced some ARM parts with up to 2MB of flash and 96KB of RAM.


For my next hobby project, I want to make a very simple two-****t
router. When the router receives a packet, it will look up the IP
address in its routing table, and then decide what ****t to forward it
out on and what destination MAC address to use. That's pretty much all
it will do. Of course I'll have to make it do a few other things, like
send and receive ARP requests, but nothing too complicated.

I started throwing some code together in notepad, just to see how I'd
make it work. Now the thing is, I see no reason why I shouldn't be
able to move this code over to a PC. Here's the beginnings of it:

typedef uint_fast32_t IPv4addr;
typedef uint_fast64_t MACaddr;

typedef struct RoutingTableEntry {
    IPv4addr addr;
    IPv4addr mask;
    IPv4addr router_addr;
    uint_fast8_t ****t;   /* Here's a great example of where I'd
normally use "unsigned int" */
} RoutingTableEntry;


typedef struct InfoForForwarding {
    uint_fast8_t ****t;
    MACaddr dst_mac;
} InfoForForwarding;

#define LEN_ROUTING_TABLE 16u
RoutingTableEntry routing_table[LEN_ROUTING_TABLE];   /* Hold 16
routes max in the table */
#define pend_routing_table (routing_table + LEN_ROUTING_TABLE)

InfoForForwarding GetInfoForForwarding(IPv4addr const dst_ip)
{
    InfoForForwarding iff =3D { 0 };

    RoutingTableEntry const *p =3D routing_table;

    do
    {
        if ((dst_ip & p->mask) =3D=3D p->addr)
        {
            iff.****t =3D p->****t;

            /* Now consult ARP table to get MAC address of router */
            iff.dst_mac =3D GetMACaddr(iff.****t,p->router_addr);

            return iff;
        }

    } while (pend_routing_table !=3D ++p);

    return iff;
}

As I hope you'll agree from looking at this code, there's nothing
microcontroller-specific or PC-specific about it. There's no reason
why the code couldn't be used to make a PC program that would
implement a "virtual router" between two network cards.

It appears that quite a few people think that PC programming and
embedded programming are quite separate from each other, but I hope my
code example above shows why there's no reason why code can't migrate
and be ****table between the two. Many C programmers already are
enthusiastic about their code being ****table, but I just hope they'd
consider microcontrollers too.

Slightly off-topically, I don't know if you've been following my
thread entitled "Ethernet in its most basic form". I've been asking
around to see what microcontroller I should use for making my little
two ****t router. I've been given many suggestions of microcontrollers
that will work with one sole ethernet ****t, but obviously I'll need a
microcontroller that will work with two. (Or then again I might need
two microcontrollers that will communicate with each other... ?). I
don't suppose you'd have any idea what I should use for that? I want
to work at 100 MBps full-duplex.