is hserin slow?

[markedwards]

I am attempting to learn how to use serial communications
using the hardware serial port (16f627A) to receive a byte of data
but it seems to slow my program. The data looks clean (no noise).
I was expecting the hserin to quickly read the receive register.
can skip hserin and I read the rcreg directly? Do I need a interrupt?
Is there a better way?

DEFINE HSER_CLROERR 1 ' Automatically clear over-run errors
define HSER_BAUD 2400
RCIF VAR PIR1.5
command VAR
reponse VAR

loop:
if RCIF then
Hserin [command]
if command = 120 then
hserout [reponse] ' respond with data
endif
gosub refresh segment display
gosub read keypad

goto loop

or

loop:
if RCIF then
command=rcreg
if command = 120 then
hserout [reponse] ' respond with data
endif
gosub refresh segment display
gosub read keypad

goto loop



Thanks,

Mark

[mister_e]

You forgot DEFINE TXSTA and DEFINE RCSTA stuff. But indeed you can read RCREG directly of course you can. will it be faster??? can't say.
Here's a link for you
http://www.picbasic.co.uk/forum/showpost.php?p=8601&postcount=11

[markedwards]

Thanks Steve!

Is RCREG 2 bytes?
I only have 1 byte to send, Should I always send 2 bytes
and always read 2 bytes?

Thanks,

Mark

[picnaut]

Hi,

I think that RCREG can only "hold" 2 bytes.
If you don't retrieve your data before that 3rd byte comes along, you get an overrun or something. It probably just kicks the first byte it received "off the end".

:)

[mister_e]

YUP! RCREG is a 2 byte buffer. This help to miss character.
You don't need to read always 2 bytes ... well yes and no. Just make a check if the RCREG is now empty will suffice.

and you just need to send 1 bytes at the time as TXREG is a single 1 byte register.

HTH

[arniepj]

Here is a couple attached demo programs that might help,written for the 16F877.Modify for you needs.One uses the on interrupt command and the other the interrupt flag.

[markedwards]

Thank You all!

I was frustrated and a little weary but your suggestions were
timely and very helpful. My serial communications are working now.

Reading RCIF & RCREG appear much faster than HSERIN.

Thanks,

Mark

[mister_e]

It's like many built-in function.
HSERIN/HSEROUT
HPWM
ADCIN
are some in the list. When you need for speed, the best way is still acess the internal register. It also produce tighter code. Built-in function are great when you don't want to break your nuts with data handling and ... and ... and.. well you know what i mean ;)