xport code, have example, confused though

[Charles Linquis]

I'm with mister_e -

ALWAYS use the hardware USART if your PIC has one!
Use a crystal when you use RS-232.

The default baud rate of an XPORT is 9600 baud.
The XPORT is a 3.3V device. Are you running it off 3.3V?

You should use a level shifter (like a 74HC gate) between the XPORTs output and the PICs input to insure that the output level of the XPORT is high enough for the PIC. In a pinch, you can use a 1K pull up resistor (to 5V) on the line connecting the ouput of the XPORT to the PICs input. Since the XPORT is 5V compliant, you don't need to do anything with the line connecting the output of the PIC to the XPORT.

[kenpo]

haven't hooked it up yet, so currently running at 0v

not sure how to run something at 3.3v is there something like a 7805?


and still no idea what USART is so I guess I'll do some reading.

xport defualt is 9600, but it can be brought down.

I'm excited to try this thing out, but I'm waiting for a breadboard compatible breakout board before I try it, rather than rush in and break something my first try.

[mister_e]

To run at 3.3 volt, yup you'll need a 3.3v voltage regulator. Now double check your specific datasheet to know if the PIC can run @3.3 volt without problem, case not, you may need to use a sort of level shifter between your PIC running @5volt and the Xport running @3.3v.

USART is just another built-in PIC feature, listed in the datasheet. You will need to use HSERIN/HSEROUT + some DEFINEs all listed in the PBP manual.

with 4MHz you can run the internal USART to have a really decent/accurate 9600 bauds.

DEFINE HSER_RCSTA 90h ' Enable serial port & continuous receive
DEFINE HSER_TXSTA 24h ' Enable transmit, BRGH = 1
DEFINE HSER_SPBRG 25  ' 9600 Baud @ 4MHz, 0.16%
DEFINE HSER_CLROERR 1 ' Clear overflow automatically

[kenpo]

thanks everyone! I'm going to muck around with all of this now!

[Charles Linquis]

You can get a 3.3V regulator. I use an LM3940
You obviously haven't read section 12 of the 16F628 datasheet - where it describes the USART!
There is no need to run the XPORT at a speed slower than 9600 baud.