AVR Freaks

I use an Arduino with a ready built library from Adafruit to run WS2812's  Should work on the WS2811.

But the Arduino UNO is a Mega328.  Not sure if the library will work on the 4809.

Jim

OK so some of the build problems I can fix and some I can't. The first stems from:

#define ws2812_PORTREG  CONCAT_EXP(PORT,ws2812_port)
#define ws2812_DDRREG   CONCAT_EXP(DDR,ws2812_port)

That is in light_ws2812.h. It is making the assumption (that is true for real tiny/mega AVR) that GPIO registers have names like PORTB and DDRB. But 4809 (because it's not really an AVR) uses Xmega naming. So the equivalent of PORTB is PORTB_OUT and the equivalent of DDRB is PORTB_DIR. Now these existing lines are trying to do something "clever" where "PORT" and "DDR" are fixed then the "B" (to pick the port)  comes from somewhere else. In fact they use:

#if !defined(ws2812_port)
#define ws2812_port B   // Data port
#endif

than all this "CONCAT()" nonsense is gluing the two bits together. So I'd actually forget all that and just go with:

#define ws2812_PORTREG  PORTB_OUT
#define ws2812_DDRREG   PORTB_DIR

replacing "B" in that with whatever port you want to use. But the next problem (I tried to use "Rainbow" as an example) is that while the port is defined in the above way they had a separate:

int main(void)
{

	uint8_t j = 1;
	uint8_t k = 1;

	DDRB|=_BV(ws2812_pin);

where they've gone and used the tiny/mega "DDRB" name again (so much for "configuration"!). So anyway you could just also change this line to be:

	PORTB_DIR |= _BV(ws2812_pin);

to use the "new name". 

However this just clears the "easy" errors but now you start getting errors like:

D:\test\test\light_ws2812.c(119,5): warning: asm operand 2 probably doesn't match constraints
		     asm volatile(
		     ^
D:\test\test\light_ws2812.c(119,5): error: impossible constraint in 'asm'

and this is a real problem. It's because the code is using things like:

    asm volatile(
    "       ldi   %0,8  \n\t"
    "loop%=:            \n\t"
    "       out   %2,%3 \n\t"    //  '1' [01] '0' [01] - re

but while you can "OUT" to "PORTB" on a Tiny/Mega you cannot OUT to PORTB_OUT on an Xmega. That's because in XMEGA all the PORT (and DIR) registers are not in range of the OUT opcode.

One might think that a simple solution would be:

    "       STS   %2,%3 \n\t"    //  '1' [01] '0' [01] - re

(change OUT to STS) but this is not going to work for a number of reasons. For one the asm() constraint says that %2 is an "IO location" but it isn't and WS2818 is so timing critical that if you change an OUT to an STS you change the number of CPU cycles so the cirtical timing will be thrown out by making such a change (and there are more OUTs to follow in the asm() too).

So the actual solution here is to use a special Xmega feature called Virtual Ports (VPORTs) that remap the PORT registers back in to the IN/OUT IO space where they should have been all along.

Only thing is that I haven't a clue how you do VPORTs on a 4809. I *think* it could be as simple as the VPORTs being configured by default as PORTA/B/C/D in which case it'd just be replacing PORTB_DIR/PORTB_OUT with VPORTB_DIR/VPORTB_OUT (or whatever weird and whacky name they've given them) and it might all work.

But as I say this isn't one I can fix as I don't have the enthusiasm to learn a whole new micro architecture - I'm happy with tiny/mega - won't care about Xmega. But perhaps someone who does use Xmega chips can advise more detail abvout VPORTs work on 4809 ??

Here is my program for the Tiny85: For the tiny10 I simply change the F_CPU.

#define F_CPU 16000000

Exactly how true is the 16000000UL in that? 

Also exactly how is this library "timed" anyway? If it too relies on knowing F_CPU then there is no point in only putting that at the top of main.c - when main () calls ws2812_setleds() how will the code in ws2812_setleds() know the CPU speed to get its timing right?

exactly as clawson explained in #19 !

Now please mark the solution - see Tip #5 in my signature.

EDIT

Rather than having to add - and maintain - the same definition in multiple source files, consider adding it to the Project options:

https://www.avrfreaks.net/commen...

https://www.avrfreaks.net/commen...