SX/B serial comms problem

Invent-O-Doc

I'm having a bit of difficulty with an apparently simple SX/B program. The program sends SEROUT bytes to an XBee device in transparent mode (serial line replacement). The SX 28 runs at 5V and the XBee at 3.3v. The signal from RB.1 goes through a voltage divider to XBee's DATA IN @ 3.2V. Certain bytes make it through, but some consistently do not. Using a full 5V signal from the SX does not make any difference. I'm using 9600 baud 8N1, true and have tried this on more than one module. Any thoughts?

PROGRAM:

DEVICE SX28, OSC4MHZ, TURBO, STACKX, OPTIONX
FREQ 4_000_000
idx VAR Byte
serb VAR Byte
PROGRAM Start
Start:
OUTPUT RB.1
FOR idx = 0 TO 9
serb = 65 + idx
SEROUT RB.1, T9600, serb
PAUSE 100
NEXT
SEROUT RB.1, T9600, 13
GOTO Start

OUTPUT SHOULD BE: ABCDEFGHIJ

ACTUAL OUTPUT: (1st char wont display here)
ÂÃDEFG IJ
ÂÃDEFG IJ
ÂÃDEFG¨IJ
ÂÃDEFG¨IJ
ÂÃDEFG IJ
ÂÃDEFG¨IJ

SX/B version version 1.51.03 onan SX/28

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Thomas Talbot, MD
Gunpowder, MD, USA

JonnyMac

You cannot use the internal clock source for serial comms -- it's not stable enough. Add a 4MHz resonator and change the DEVICE line to OSCXT1

Invent-O-Doc

Doh, I didn't see that that tag didn't change! Of course you are right! Thanks!

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Thomas Talbot, MD
Gunpowder, MD, USA