[En-Nut-Discussion] problem using fflush() (Klaus Kloos)

[Klaus Kloos]

Hello Ole
> 
> 
>> 	    outr(PIOA_PDR, _BV(1));     	// PIO Disable Register
>> 	   zeichen = 0;
>> 	   gesendet = fwrite(&zeichen, 1, 1, dmxOut);			// Startcode=0
>> 
>> 	    gesendet = fwrite(buffer, 1, 512, dmxOut);
here is the 200us delay
>> 	    fflush(dmxOut);
>> 	    NutSleep(10);
> 
> After disabling the PIO, the UART will gain back the control. You will
> see the default UART output level, until the data transmissions starts.
> It might take additional time until the first data is send out, as some
> thread switching might be needed before.
> 

Ive seen this while debugging, but that not 200us.
There is new understanding on my side. The delay is coming from the fwrite(buffer, 1, 512, dmxOut). 
If I write all the bytes one by one there is no delay. Using fflush() after each byte or after the block, does no change this.

	    #define blockgroesse 1	// 2^n, works up to 4, 8 generates delays
	    for(lauf=0; lauf<512/blockgroesse; lauf++){
			gesendet = fwrite(&buffer[lauf*blockgroesse], 1, blockgroesse, dmxOut);
	    }
	    fflush(dmxOut);

This is a solution for my needs, but there seems to be a problem.

> So you might better want to implement the break function directly into
> the UART driver.
> 
I think thats beyond my possibilities at the moment. Ethernut  and even ARM is new for me. Where to start? Is there an example somewhere?

Thanks and greetings
Klaus