Arduino send HEX values via XBee - arduino

Question

I'm trying to send HEX values via XBee from a Arduino to digi's Xbee program XCTU. But i have some problems with some bytes that i cant send
The list of bytes i cant send:
0x11
0x13
0x7D
0x7E
0x81
0xEC
0xEE
If i use any other bytes i can see it in the XCTU console window and i get a response back to the Arduino
I have enabled API mode (AP=1) on both of the Xbee's. Im using the XBee lib linked from Arduino web site (https://www.arduino.cc/en/Reference/Libraries)
My code looks like this:
#define XBEE_RX_PIN 8
#define XBEE_TX_PIN 9
SoftwareSerial xbeeSerial(XBEE_RX_PIN, XBEE_TX_PIN);
void setup()
{
Serial.begin(9600);
xbeeSerial.begin(9600);
xbee.begin(xbeeSerial);
}
void loop()
{
Serial.println("Send next 255 msg:");
uint8_t testMsg[1] = { 0x0 };
for (uint8_t i = 0; i <= 0xFF; i++)
{
test2[0] = i;
Tx16Request testTx = Tx16Request(0xFFFF, testMsg, sizeof(testMsg));
xbee.send(testTx);
Serial.print("Message send: ");
Serial.println(test2[0], HEX);
if (xbee.readPacket(5000)) {
Serial.println("SUCCESS");
}
else if (xbee.getResponse().isError()) {
Serial.println("isError");
}
else {
Serial.println("No Response");
}
}
Serial.println("");
delay(3000);
}

Answer 1

With AP=1, you can't send some special bytes like:
0x7E (start of frame)
0x11/0x13 (XOn XOff)
...
As mentioned in the XBee documentation (XBee®XBee-PRO® ZB RF Modules manual 90000976_W.pdf, starting page 112), you should use AP=2 mode which allows you to transmit these special bytes by escaping them:
Escape characters.
When sending or receiving a UART data frame, specific data values must be
escaped (flagged) so they do not interfere with the data frame sequencing.
To escape an interfering data byte, insert 0x7D and follow it with the byte to be escaped XOR’d with 0x20.
Note that, if not escaped, 0x11 and 0x13 is sent as is.
Data bytes that need to be escaped:
- 0x7E – Frame Delimiter
- 0x7D – Escape
- 0x11 – XON
- 0x13 – XOFF
Example - Raw UART Data Frame (before escaping interfering bytes):
- 0x7E 0x00 0x02 0x23 0x11 0xCB
0x11 needs to be escaped which results in the following frame:
- 0x7E 0x00 0x02 0x23 0x7D 0x31 0xCB
Note In the above example, the length of the raw data (excluding the checksum) is 0x0002 and the checksum of the non-escaped data (excluding frame delimiter and length) is calculated as:
0xFF - (0x23 + 0x11) = (0xFF - 0x34) = 0xCB.
Hope this helps