High Speed Serial Comm PC - PIC and PIC - PIC

[SteveB]

By the way, I would like to know what is the benefit of using the USART module, with hserin or hserout commands, as they cannot be done in the backgroud. The benefit is clear, though, when using the module just like the datasheet says.
Perhaps you can achieve greater speeds using the USART??? Or less error percentage???

Manuel,

The advantage of the PBP HSEROUT command is that it has the flexability to
a) "format" the outgoing data as needed (such as sending the value 65 out as "65", "41", "A", or "01000001") and
b) send multiple bytes in sequence (such as HSEROUT [dec var_a, 10, "X", HEX2 var_b]) and
c) it uses the hardware USART, which speeds things along, since it change run at a higher baud rate and it can send out one byte in the background while the pic is processing the next byte in the foreground.

The disadvantange to the HSEROUT is that it will occuply the PIC if it has a large amout of data to send. Take, for example, the command:
HSEROUT ["This is a long string of data for the PIC to send out the USART!"]
This command, even though it uses the USART, would monopolize the PIC until the last byte was sent to the USART. So, it is very much running in the forground (preprocessing and queing the data), even though it uses the hardware USART in the background to actually send the data.

What about writing directly to the TXREG? If the data did not need any "pre-processing", and in combination with an interrupt driven queing scheme, this would likely be the fastest, most efficient method, leaving more time for foreground processing. The foreground task is only interrupted, when the USART is done sending the last byte, long enough to write the next byte to the TXREG. It then resumes the foreground processing until the USART is done sending out that byte. This is not the "easiest" way to do things, just another alternative.

Now, what you need to determine is how critical timing and processing time are going to be in your application. If your forground tasks are not that demanding, the HSEROUT, sending a burst of 96 bytes would be the easiest. Otherwise, you may need to set up an interrupt based scheme which will take maximum advantage of the USART.

As for percentage of error, since the HSEROUT uses the USART to send the data, the timing error is the same. How it compares to the timing error of PBPs bit-banged serial commands? I haven't got any data on that.

Steve B