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Re: [avr-gcc-list] Problems with ATMEGA8 USART

From: Dave Hylands
Subject: Re: [avr-gcc-list] Problems with ATMEGA8 USART
Date: Tue, 16 Aug 2005 19:06:00 -0700

Hi David,

> > The one clumsy part of code was in my_putchar() which had to reach
> > directly into the hardware for the specific port to restart the Tx
> > IRQ if the buffer had been empty, which causes my Tx IRQ routine to
> > shut itself off. Also there was a possible race condition.

Why not just store a copy of the UCSRxB register inside your Uart structure?

typedef struct
   ...other members...

   volatile uint8_t *ucsrb;
} Uart;

Then initialize the member

fp->ucsrb = &UCSR0B;

and in your putc routine:

*fp->ucsrb |= ( 1 << UDRIE );

If the shifts for the interrupt enable are different you can store
those in the structure as well.

Dave Hylands
Vancouver, BC, Canada

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