hello_world_small Uart input

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originally posted by jakobjones@Feb 15 2007, 10:00 PM

i realize that this post is old and you probably already found a solution but here you go anyway:

# include "altera_avalon_uart_regs.h"

char ch;

ch = iord_altera_avalon_uart_rxdata(uart1_base);

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What if you are polling for a UART character? That command will just dump whatever&#39;s in the register, regardless of whether there&#39;s something there. I tried using this before reading the post, and I just get into a massive loop because there is no event that the code waits for.

I believe that you need to look at RRDY in the _STATUS register (bit mask 0x0080) to see if there&#39;s a byte there. I have been trying this, but I&#39;m getting "blank" data back. I believe that it&#39;s because I&#39;m also using printf() HAL functions, which the datasheet refers to there being a problem running both register access and HAL at the same time.

I&#39;m having issues with a "small" build, and the getchar() and file i/o methods seem to work fine, but don&#39;t compile properly when targeting a device that does not have enough room to cram a "full" C library (EP2S15).

Does anyone have a solution for polling for a UART character w/out getchar() or getc()?

I suspect that I could stop using fprint() - HAL, and do all of the character I/O using IOWR_ALTERA_AVALON_UART_TXDATA(UART_0_BASE, data) commands, but rewriting fprint() is not too appealing, since I&#39;m a hardware/FPGA guy that&#39;s dabbling in C.

Any thoughts/comments on this would be appreciated.

Thanks,

Jeff