I use the free SDCC compiler for 8051 projects. Doing anything for the first time is tough, but learning C is well worth while. I don't know how you load code in to your SBC, but I assume it's got an RS232 port. I would try writing a main() function that prints "Hello World" out of the serial port repeatedly:

void main(void)
{
    for(;;)
    {
        printf("\n\rHello World");
    }
}

Then all you need to do is write putchar and getchar functions, which the compiler will link to!

It's easier said than done, but you have to start somewhere.

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