Problem using 2 rs232 ports on 18f8722

Hern�n · Guest

Hello,

I'm using 2 rs232 ports with the PIC18f8722 in order to communicate with a PC and a GSM module. The thing is both communications seem to work fine in the beginning, but as soon as I send some information to the PC, the communication with the module starts to fail. I still can send info to the module, but I can`t receive from it. Using the very same code but not transmitting first to the PC the program works, and a very similar program communicating to a WiFi module instead of the GSM one works too (including the PC part).

Is there any issue about using both rs232 that I should know of? did anyone have this problem, or alike, before?

Thank you.

Mark · Joined: 07 Sep 2003 Posts: 2838 Location: Atlanta, GA

Be sure to include "ERRORS" in you #use RS232 statement.

ALFA 705 · Joined: 03 Jun 2005 Posts: 9

Hi,

I had SERIOUS problems with 18F8722 using the two UARTS at same time.
An Errata about that is showed on www.microchip.com

I hope this help you. If you need further detatais....

ALFA 705

Hern�n · Guest

Hi,

Thank you for the replies.

ALFA, I've scanned throught the erratas concerning 18f8722 in the microchip webpage, but were unable to find the one relating to the problem about using both UARTs at the same time, could you please give me some more details about it?

Thank you again.

ALFA 705 · Joined: 03 Jun 2005 Posts: 9

Hernan,

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1335&dDocName=en010327

This errata says "...when performing BACK-TO-BACK transmision..."
Yes, this errata only mention for 9 bits but you have believe me, in 8bits fails too under some conditions.

I receive from one EUSART and send to other the EUSART. In some cases (random) the PIC inserts an extra "0x00". Microchip say me that is an ERRATA.
Silicon revison is scheduled for next year 2007 !!!!!! Incredible.
Sorry for my Englsh.

ALFA 705